Class 10

UP Board Notes for Class 10 Science Chapter 10 Nervous System

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UP Board Notes for Class 10 Science Chapter 10 Nervous System Learning Objectives

After completing this chapter, you will be able to:

  • State the functions of the nervous system;
  • Describe the structure of a neuron, list its various types and state their specific functions;
  • Describe the transmission of nerve impulses across a synapse,
  • Categorize nervous sytem into central and peripheral nervous systems;
  • List the parts of CNS and state their functions;
  • Describe the structure of the brain and the spinal cord and explain their functions;
  • Describe the structure and functions of peripheral nervous system;
  • Differentiate between sympathetic and parasympathetic nervous systems.

We perform many activities consciously or unconsciously, for example, when we eat food, our eyes help to locate the food, the nose smells it, hands bring the food to the mouth, teeth chew and masticate it, the tongue pushes the food inside the alimentary canal, and so on. All these activities occur in a coordinated manner. The organ system in our body, which brings about coordination and integration of body activities is the nervous system. In this chapter, you will learn about the nervous system in the human body.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Major Divisions of Nervous System

  • The nervous system in human beings is divided into two main parts.
  1. Central nervous system (CNS): It includes the brain and the spinal cord, and is the site of information processing in the nervous system.
  2. Peripheral nervous system (PNS): It consists of nerves that emerge and enter the brain and spinal cord and run between the CNS and different parts of the body. These nerves are divided into three groups sensory or afferent nerves that transmit information to the CNS, motor or efferent nerves that carry messages from the CNS to the effector organ, and mixed nerves.
  • The PNS is further divided into two sub-divisions:
  1. The somatic nervous system (SNS) regulates voluntary activities and transmits messages to the skeletal muscles.
  2. The autonomic nervous system (ANS) works independently to regulate involuntary activities. It consists of nerves and ganglia which connect the visceral organs like smooth muscles of heart, lungs, digestive tract and other internal organs and perform a variety of involuntary actions that are not under the control of our will.
  3. It has two components, viz. sympathetic and parasympathetic, which are antagonistic (opposite) to each other in their functions. You will learn about the autonomic nervous system in a later section.
  • The broad organization of nervous system in humans is shown in Let us first learn about nerves and functioning of the nervous system before discussing about the two divisions of nervous system.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Nervous System Nerves

  • Nerves are composed of nerve fibers (axons) of separate neurons bundled together like the wires of a telephone cable enclosed by a tubular sheath. These nerve fibers or nerve cells are called neurons which form the basic unit of the nervous system.
  • The  Structure of Nervous system is shown below.

Nervous-System-Organization-of-the-nervous-system-in-human-beings

Nervous System Structure of the human nervose system

 

  • A neuron is the longest cell in the body. It receives information and transmits it from one part of the body to another part. Thus, a neuron is the structural and functional unit of nervous system and is highly specialized for responding to stimuli.
  • Messages are conducted by nerves in the form of electrical impulses.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Types of Nerves

  • There are three types of nerves depending upon the direction in which they transmit the impulse.
  1. Sensory nerves: These are also called afferent nerves (afferent: carry toward). These nerves contain sensory fibers which carry messages (impulses) from sensory receptors (in sense organs) toward the brain or spinal cord. Example: Optic nerve from eye leading to brain.
  2. Motor nerves: These are also called efferent nerves (referred: to carry away). The nerves contain motor fibers which take messages away from the brain or spinal cord towards the effector organ (such as muscles and glands). Example: Nerves arising in rain and leading to the muscles of the eyeballs for rotating it.
  3. Mixed nerves: These nerves comprise both sensory and motor nerve fibers. Example: Most cranial and spinal nerves are mixed nerves.

Ganglia (singular: ganglion)

These are the aggregate of nerve cells from where the nerve fibers arise.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Structure Of A Nerve Cell (Neuron)

  • Each nerve cell consists of three main parts.
  1. Cell body or cyton
  2. Dendrites
  3. Axon

1. Cell body:

The cell body or cyton (or Perikaryon) has a large, central nucleus surrounded by the granular cytoplasm. The cytoplasm contains (also called neoplasm) Nissl granules and neurofibrils. It has all the cell organelles (like mitochondria, Golgi apparatus, endoplasmic reticulum, microfilaments, and microtubules). There is no centrosome in the cyton because the nerve cells have lost the ability to divide.

Nervous-System-A-nerve-cell-or-neuron

2. Dendrites (dendron: tree): These are short, thread-like branches which arise from the cell body. The dendrites conduct nerve impulses to the cyton.

3. Axon: One of the branches (of dendrites) grows very long in comparison to others. This branch is called the axon. The axon is covered on the outside by three layers.

  • Axolemma (the innermost layer)
  • Myelin sheath or medullary sheath (the middle layer)
  • Neurolemma (the outermost white insulating sheath)

The axolemma and neurotrauma are continuous sheaths, whereas the myelin sheath is not a continuous one. The myelin sheath shows gaps across its length at intervals. These gaps are known as nodes of Ranvier.

The axon ends have swollen bulb-like ends which store acetylcholine (a neurotransmitter). These are called axon endings. Axon endings are closely placed near the dendrites of another neuron but are not connected. Such gaps in between are called synaptic clefts or synapses.

Synapse

  • The neurons are not attached to each other. There is a small gap between them. The fine gap or loose connection between the axon endings of one nerve cell and cyton or dendrite of the next nerve cell is called the synapse. We can also say that the point of contact between two neurons is known as synapse. Signals travel from one neuron to another neuron across these junctions.

Structure of the synapse

The neurons do not touch at the synapse. The space between adjacent neurons is called the synaptic cleft.

  • The axon terminal of a presynaptic neuron has a bulb-like appearance known as a synaptic bulb  The transmission.
    across synapses is done by chemical means. The synaptic bulb contains chemicals known as neurotransmitters.
  • When a nerve impulse (action potential) arises at the axon terminal, it causes synaptic bulbs to release neurotransmitters in the synaptic cleft. chemical transmitter
  • These neurotransmitters diffuse easily across the synaptic cleft. In this way, the impulse is transmitted from one nerve cell to another nerve cell.
  • There are many neurotransmitters but the principal ones are acetylcholine and norepinephrine.Nervous-System-Structure-of-the-synapse

What does a synapse do?

  • Allows information to pass from one neuron to another.
  • Ensures that the nerve impulse travels in one direction only.
  • Allows the adjoining neuron to be excited or inhibited.
  • Amplifies a signal (makes it stronger).
  • Helps in information processing by adding together the effects of all impulses received.
  • Filters out low-leveled stimuli.

There are three types of neurons:

  1. Sensory neurons: These carry impulses from sense organs to the brain or spinal cord.
  2. Motor neurons: These carry impulses from brain or spinal cord to effector organs (muscle or gland).
  3. Association neurons: These interconnect sensory and motor neurons.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Communication Through The Nerve – Nerve Impulse

The nervous system receives a stimulus through a receptor organ, integrates or coordinates it, and effects a response through the effector organ. Thus, coordinated behavior has six main components – stimulus, receptor, impulse, coordinator, effector, and response.

  • In such a coordinated behavior, any stimulus of sound, sight, smell, etc., is perceived by receptor organs like eyes, ears, skin, etc.
  • A stimulus is an agent or sudden (external or internal) change that results in a change in the activities of an organism.
  • An impulse is a wave of chemical disturbance that travels through the nerve cell.
  • Receptors are sensory organs that receive stimulus and send waves in form of impulses towards CNS (coordinator).

Nervous-System-Components-of-coordinated-behavior

  • Effectors are the muscles or organs which show response due to motor nerves. Response is a change that occurs in an organism due to a stimulus.
  • The brain and spinal cord are the coordinators that receive information in the form of messages called nerve impulses, from receptor organs via neurons. The information flows to the effector organs, i.e. muscles, which contract or relax or secrete substances to show response.

Nervous-System-Flow-chart-showing-direction-of-nerve-impulse

Transmission of the nerve impulses

  • Nerve impulses pass along a neuron in one direction only. At one end, the neuron is connected to a sensory receptor that receives the stimulus and converts it into electrochemical waves which are carried by the neuron. The nerve fiber at this stage is said to be excited.

Nervous-System-Transmission-of-nerve-impulse-through-a-synapse

  • The events that take place during the conduction of an impulse along a nerve are given as follows.

UP Board Notes for Class 10 Science Chapter 10 Nervous System At Resting State – Polarised state

At normal (resting) state, the outer side of the nerve fibers carries more positive (+) charge due to more Na* ions outside the axon membrane. This is called a polarised state.

Nervous-System-Polarised-state-of-nerve-fiber

UP Board Notes for Class 10 Science Chapter 10 Nervous System At Stimulated (excited) state – Depolarisation

  • On receipt of a stimulus, the axon membrane at the place of stimulus becomes more permeable to Na+ ions and as a result, the Na* moves inside causing loss of polarity, i.e. depolarization. This region, thus, becomes an exciting region. This region of depolarisation moves forward to next area which in turn becomes depolarised.

Nervous-System-Depolarisation-of-nerve-fibre

UP Board Notes for Class 10 Science Chapter 10 Nervous System Returning To Normal State – Repolarisation

  • The previous area (which has received stimulus) becomes repolarised due to active transport of Nat ions outside. This transport is achieved by sodium pump for which energy in the form of ATP is required. Thus, conduction of nerve impulses is a wave of depolarisation followed by repolarisation.

Nervous-System-Transmission-of-nerve-impulse

UP Board Notes for Class 10 Science Chapter 10 Nervous System Central Nervous System

  • The central nervous system consists of the brain and The spinal cord.

The human brain

  • The human brain is a highly developed organ and is situated in the cranium (brain box) of the skull. In an adult, it weighs about 1200-1400 g, about 2% of body weight.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Covering Of Brain (Meninges)

  • The brain is covered on the outside by membranes called meninges (singular: menix ). Meninges are protective coverings of the brain which consist of three layers.

Nervous-System-Parts-of-the-human-brain

Meningitis

The inflammation (swelling) of the meninges is known as meningitis.

  • The outer tough, protective layer dura mater is formed of fibrous tissue.
  • The middle arachnoid layer is a delicate membrane which gives a web-like cushion.
  • The inner thin, transparent, and highly vascular layer the pia mater. It is richly supplied by blood.

The cerebrospinal fluid

  • It is the watery fluid which fills the spaces between the meninges and also brain cavities or the ventricles. It also acts like a cushion to protect brain from shocks.

Parts of the brain

  • The human brain is divisible into three major parts
  1. Forebrain
  2. Midbrain
  3. HindbrainNervous-System-Divisions-of-the-human-brain-and-their-components

UP Board Notes for Class 10 Science Chapter 10 Nervous System Forebrain

  • It is the anterior region of the brain. It has the following parts:
  • Cerebrum (seat of intelligence, memory, consciousness, and voluntary action)
  • Diencephalon (thalamus, hypothalamus, pineal and pituitary glands)

1. Cerebrum (L. cerebrum: brain)

The cerebrum is the main part of forebrain.

  • Cerebrum is the largest and the most prominent part of the brain. It is divided into two halves – the right and left cerebral hemispheres.
  • The two hemispheres are connected by a thick band of nerve fibers called corpus callosum. Corpus callosum helps in the transfer of information from one hemisphere to another.Nervous-System-Different-regions-of-the-brain-are-associated-with-different-functions
  • Each hemisphere is hollow internally and its walls have two regions an outer cortex and an inner medulla. The outer portion or region of the cerebrum (cerebral cortex) contains cell bodies of neurons and is called grey matter (due to its greyish in color).
  • The layer of grey matter is highly convoluted in appearance with ridges and grooves. The fold of ridges are called gyri (singular: gyrus) and depressions (grooves) between them are called sulci (singular: sulcus). The ridges and grooves increase the surface area for more nerve cells.
  • The number and pattern of convolutions in the cerebrum are associated with the degree of intelligence.
  • The inner region of the cerebrum consists of white matter that has axons of nerve cells.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Functions Of Cerebrum

  • Because of highly developed grey matter the cerebrum governs mental abilities like thinking, reasoning, learning, memory, and intelligence.
  • It also controls all voluntary functions; willpower, emotions, and speech.
  • It enables us to observe things around us through sense organs.
  • It also controls feelings of love, admiration, and hatred. Centers for subconscious mind are also located in the cerebrum. Overall the cerebrum is the seat of intelligence, memory, and willpower.

2. Diencephalon

  • The diencephalon mainly consists of the pineal gland, pituitary gland, thalamus, and hypothalamus. It encloses a cavity called the third ventricle. The thalamus is a relay station for sensory impulses going to the cerebrum. The hypothalamus is situated at the floor of the brain and helps in thermoregulation.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Functions Of Diencephalon

  • The diencephalon contains reflex centers for muscular and glandular activities. It also has centers of emotions, hunger, and thirst. It also helps in controlling the body temperature (thermoregulation) and water-salt balance in the body (osmoregulation).

UP Board Notes for Class 10 Science Chapter 10 Nervous System Midbrain

  • It is a thick-walled structure and is a smaller portion of the brain. The midbrain or mesencephalon connects the anterior region of the brain to the posterior region and therefore all nerve fibers pass through this region. On the dorsal side of the midbrain lie optic lobes which control vision.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Hindbrain

  • The hindbrain has three main parts.
  1. Cerebellum
  2. Pons
  3. Medulla oblongata

1. Cerebellum (Little brain)

  • The cerebellum is situated in the dorsal region. of the hindbrain. Cerebellum is a much smaller area and is located at the base under the large cerebrum.
  • There are no convolutions, but many furrows.
  • It has an outer cortex made of grey matter and an inner section consisting of white matter.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Functions Of Cerebellum

  • It maintains body balance and controls muscular activities. It makes the body movements smooth, steady, and coordinated. It regulates and coordinates contraction of skeletal muscles.

2. Pons

  • Pons forms the part of the brain stem at the floor of the hindbrain. It is a bridge of transverse nerve tracts extending from the cerebrum to the cerebellum. It also connects the forebrain to the spinal cord.

3. Medulla oblongata

  • The medulla oblongata is the third main part of the hindbrain. It is the lowermost part of the brain located at the base of the skull. It is continued as spinal cord in posterior region.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Functions Of Medulla Oblongata

  • It contains vital reflex centers, such as cardiac center, respiratory center, and centers for swallowing,\ sneezing, and coughing. Thus, it controls involuntary functions of the body like a heartbeat, swallowing, and breathing.
  • Injury to medulla oblongata may lead to death
    Medulla oblongata is main part of the hindbrain. It controls vital reflex centers and Involuntary functions like heartbeat, breathing, and swallowing of food. Any Injury to medulla oblongata will affect these functions and may cause death due to stopping of the heartbeat and breathing.

Nervous-System-Main-functions-of-various-parts-of-the-brain

UP Board Notes for Class 10 Science Chapter 10 Nervous System Nervous System Spinal Cord

  • The spinal cord is a cylindrical, long cord which arises from the medulla oblongata and runs along the vertebral column. It passes through the neural canal of the vertebral column. Like the brain, it is also protected by the three meninges, cerebrospinal fluid, and a cushion of adipose tissue.
  • In the transverse section of spinal cord, a central canal can be seen. This canal is filled with cerebrospinal fluid. Immediately surrounding the canal are clusters of cytons which form the grey matter. In the peripheral part, axons are concentrated and this area is called the white matter.
  • On each side of the spinal cord, there are two horns, the dorsal horn, and the ventral horn. The dorsal root ganglion contains the cell bodies of sensory neurons. A nerve joined to the dorsal horn or dorsal root ganglion picks up sensations from various organs. It is called the sensory nerve.
  • The ventral root contains the axons of large motor neurons. The cell bodies of these motor neurons are located in the spinal cord. Thus, from the ventral horn or ventral root, the motor nerve arises which takes the messages from the spinal cord to the organs concerned.

Nervous-System-structure-of-the-spinal-cord
Nervous-System-components-of-reflex-arc

UP Board Notes for Class 10 Science Chapter 10 Nervous System Functions Of The Spinal Cord

  • It is the center for reflex actions. The spinal cord conducts reflexes below the neck.
  • It conducts sensory impulses from skin and muscles to the brain.
  • It conducts motor responses from brain to the muscles of trunk and limbs.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Reflex Arc And Reflex Action

  • There are certain body responses that are immediate and do not require any processing by the brain. These responses or actions are controlled by the spinal cord. These are called reflex actions.
  • A reflex action may be defined as a spontaneous, automatic, and mechanical response to a stimulus controlled by the spinal cord without the involvement of the brain.
  • The pathway followed by sensory and motor nerves in a reflex action is called the reflex arc.

Components of a reflex arc

  • A reflex arc has four main components.
  1. Receptor or sensory organ to perceive the stimulus.
  2. Sensory or afferent nerve that carries the message from receptor to the spinal cord.
  3. Relay or association neurons of the spinal cord that transmit impulses from the afferent (sensory) neurons to the efferent (motor) neurons.
  4.  Motor or efferent nerve that carries the message from the spinal cord to the muscles or glands (effector organ).
  • The entire sequence of events that constitute a reflex arc are summarized in.

UP Board Notes for Class 10 Science Chapter 10 Nervous System Nervous System Reflexes

  • There are mainly two types of actions – voluntary actions and involuntary actions.
  • Voluntary actions are those actions which are performed consciously. For example, if you wish to play, or switch on TV to watch some programs are voluntary actions.

Nervous-System-Sequence-of-events-in-a-reflex-arc

  • Involuntary actions are those actions that occur unknowingly without our will. For example, you withdraw your hand when it accidentally touches a hot iron; or you start shivering if it is too cold or you start sweating when it is too hot. All involuntary actions are reflexes and involve some kind of sensory stimulation. Differences between voluntary and involuntary actions are given in Table.

Nervous-System-Differences-between-voluntary-and-involuntary-actions

UP Board Notes for Class 10 Science Chapter 10 Nervous System Types Of Reflexes

  • There are two types of reflexes:
  •  Simple or natural reflexes
  •  Conditioned or acquired reflexes

1. Simple or natural reflexes are those reflexes that do not require any previous learning experience. Such reflexes are inborn and inherited from parents.

Some examples of simple reflexes are:

  • Blinking of eyelids in response to a foreign particle that approaches the eye.
  • Closing of the eyelid in response to a strong beam of light being flashed on the eyes.
  •  Withdrawal of the leg, if you suddenly step on a nail.
  • Knee-jerk response, if a sharp tap is made below the kneecap, then the leg is involuntarily extended.
  • Sneezing when any irritant enters the nose.
  • Coughing when the swallowed food wrongly enters the windpipe. Immediate withdrawal of hand, if suddenly pricked by a thorn or after touching a hot object.
  • Peristaltic reflex to allow movement of food (chyme) when intestine becomes full and distended.

2. Conditioned or acquired reflexes are those which develop due to some previous experience or training. The conditioned reflexes are not inborn and result due to some learning in one’s lifetime.

Some examples of conditioned reflexes are:

  • Watering of mouth (salivation) at the sight of tasty food.
  • Applying sudden brakes of your bicycle if someone suddenly comes in front.
  • Typing on the keyboard of a computer.
  • Playing a musical instrument such as guitar.
  • Surfing the channels while watching the television.
  • Tying one’s shoelace.
  • The hand signal automatically shows direction to turn the cycle without thinking.Nervous-System-Differences-between-simple-and-acquired-(or conditioned)-reflex

UP Board Notes for Class 10 Science Chapter 10 Nervous System Peripheral Nervous System

  • The peripheral nervous system (PNS) comprises the nerves that connect the central nervous system with different parts of the body.
  • Peripheral nervous system is divided into two subdivisions- somatic nervous system and autonomic nervous system.

1. Somatic nervous system

  • The somatic nervous system includes both motor neurons and sensory neurons. The fibres of motor and sensory neurons are bundled together into nerves, which are of two types.

Nervous-System-Autonomic-nervous-system-showing-sympathetic-and-parasympathetic-divisions

  • Cranial nerves connected directly to the brain, such as the optic nerve (for eye), auditory nerve (for ears), mixed nerves (for face), etc. There are 12 pairs of cranial nerves.
  • Spinal nerves emerge from the spinal cord. There are 31 pairs of spinal nerves. Every spinal nerve is a mixed nerve having both sensory and motor nerves.
  • The somatic nervous system regulates voluntary activities while the autonomic nervous system performs a variety of functions that are not under the control of an individual.

2. Autonomic nervous system

The autonomic nervous system (ANS) includes a chain of 22 pairs of ganglia that lie close to the spinal cord and are associated with the organs they control. ANS is primarily a motor system consisting of neurons that control the functioning of many organs.

  • Heart muscles
  • Glands
  • Smooth muscles (muscles of blood vessels, digestive, respiratory, and reproductive tracts) The ANS can stimulate or inhibit the activity of its target organs. The ANS is divided into two divisions -sympathetic and parasympathetic nervous systems.
  • These two divisions are anatomically and functionally distinct. The sympathetic fibers arise from the thoracic (chest) and lumbar (waist) region of the spinal cord, whereas the parasympathetic fibers arise from the brain and the sacral (pelvic) region of the spinal cord.
  • The effect of the two systems is antagonistic. In general, the sympathetic system stimulates a particular function and prepares the body for violent actions against unusual emergency conditions, while the parasympathetic system has an inhibitory or calming down effect, i.e. it re-establishes normal conditions after the violent action is over. The major differences between sympathetic and parasympathetic nervous systems are given in Table.

Nervous-System-Effect-of-sympathetic-and-parasympathetic-nervous-systems-on-major-organs

UP Board Notes for Class 10 Science Chapter 10 Nervous System Nervous System Summary

  • The nervous system in humans is divided into two parts: central nervous system and peripheral nervous system.
  • The central nervous system includes the brain and the spinal cord and is the site of information processing in the nervous system.
  • The peripheral nervous system consists of nerves that run between central nervous system and different parts of the body.
  • The structural and functional unit of the nervous system is a highly specialized cell called a nerve cell or neuron. Each neuron has three principal parts – the cell body or cyton, the axon, and dendrites.
  • Nerves can be sensory, motor, or mixed.
  • The nervous system receives a stimulus through a receptor organ, integrates or coordinates it, and effects a response through the effector organ.
  • The human brain has three main divisions the forebrain comprising of cerebrum and diencephalon, the midbrain, and the hindbrain comprising of the cerebellum, pons, and medulla oblongata.
  • The cerebrum is the largest and the most prominent part of the brain. It has ridges and grooves (girl and sulci) which increase surface area for nerve cells. The outer cortex of cerebrum contains grey matter. Cerebrum governs mental abilities like thinking, reasoning, learning, memorizing, intelligence, will, and emotions. lotions.
  • Cerebellum is the smaller part located at the base under the large cerebrum. It maintains body balance and controls postures and coordinates muscular activities.
  • Medulla oblongata is the lowermost part of the brain located at the base of the skull. It contains vital reflex centers and controls the activities of the internal organs.
  • The spinal cord is a long cord that arises from the medulla oblongata and runs along the vertebral column.
  • Reflex action is a spontaneous, automatic, and mechanical response to a stimulus controlled by the spinal cord without the involvement of the brain. Sympathetic and parasympathetic nervous systems are two divisions of autonomic nervous system and these are antagonistic (opposite to each other) in their functions.

UP Board Notes for Class 10 Science Chapter 15 Human Evolution

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UP Board Notes For Class 10 Science Chapter 15 Human Evolution Learning Objectives

After completing this chapter, you will be able to:

  • Define the term evolution;
  • Describe the evolution of humans;
  • Discuss and describe the morphological features of human ancestors;
  • List theories of evolution;
  • Describe Lamarck’s theory of inheritance of acquired characteristics with examples;
  • Describe Darwin’s theory of natural selection: survival of the fittest.

The process of evolution involves a gradual irreversible change or variation in the organisms generation after generation. t means that the organisms of the present day have arisen from ancestors who were more simple in organization.

The following are the causes of evolution:

1. Variations in the gene pool of members of a population.
2. Natural selection favouring accumulation of advantageous variations.
3. Genetic drift or chance selection.

The word evolution has been derived from a Latin word evolvere (L. e: out; volvo: to roll) means to unroll or unfold to reveal modifications or gradual changes. Therefore, evolution is defined as a naturally occurring slow, continuous and irreversible process of change.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Evolution Of Human

In order to study the evolution of man, various tools such as time dating, excavating and studying fossils as well as determining DNA sequences have been used. There is a great diversity of human forms and features across the planet.

Earlier, skin colour used to be the commonest way of identifying human races. However, there is no biological basis to this notion of human races. All humans belong to a single species, Homo sapiens.

Place of origin of human

  • The family of humans (Hominidae) evolved about 20 million years ago. At the same time, its close relatives, the family of chimpanzees, gorillas and orangutans (Pongidae) diverged from it.
  • The fossils of prehuman and ancestral human forms are found in East Africa, Asia and Europe, indicating that human’s centre of origin was probably in Africa. The evolution of bipedalism marks the beginning hominids. Hominids is a term used for humans and their immediate ancestors.
  • Humans, Homo sapiens, evolved about 1.5 million years ago. The Homo sapiens evolved further to the Neanderthal man followed by the Cro-Magnon man and further the Modern man.

In 1871, Charles Darwin published a book named The Descent of Man. In this book, he suggested that humans evolved from same African ape ancestors that gave rise to the gorillas and chimpanzees.

How did they migrate?

The genetic footprints of humans can be traced back to the African roots. About two-three hundred thousand years ago, some of human ancestors migrated from Africa to West Asia, then to Central Asia, Eurasia, South Asia and East Asia. Then, these ancestors travelled down the islands of Indonesia and the Philippines to Australia. From Australia, they crossed the Bering land bridge to America. They went forward and backward, even moving in and out of Africa. There were various factors such as availability of food, habitat and environmental suitability which directed human evolution.

Evolutionary changes in humans

1. Erect posture (to stand and walk straight)
2. Bipedal locomotion (to free forelimbs)
3. Forelimbs adapted to hold objects
4. Increase in brain size and its complexity (to think intelligently and logically)
5. Articulation of speech for better interaction and communication
6. Formation of chin
7. Reduction in the size of canines
8. Loss of brow ridges.

Human-evolution-Summary-of-human-evolution-1

Ancestors of human beings

The Lemur and Loris are said to be the early ancestors of human beings. Lemur is a small monkey-like animal with a long tail. It lives on trees. The Lemur is the oldest of living primates. A fossil ape Dryopithecus is considered to be the common ancestor of humans and great apes (orangutan, chimpanzee and gorilla). It had large brain, large canines, and feet fossils indicate its semi-erect posture.

Human-evolution-Evolution-of-humans

The prehistoric man Ramapithecus, lived some 15 million years ago, evolved from Dryopithecus. Dryopithecus was more ape-like while Ramapithecus was more man-like hominid.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Australopithecus

Australopithecus are believed to have appeared some 3.9 million years ago in grasslands of East Africa. They were able to walk or run on two legs but still retained many ape-like features including adaptations of tree-climbing (long arms, short legs), a small brain, a long protruding jaw, and cone-shaped ribcage.

The cranial capacity was about 400-600 cubic centimetres (cc) and they were 1.2 to 1.5 metres tall. They had a low, sloping forehead, brow ridges projecting over the eyes and a projecting face.

Canine teeth were pointed and of size between that of apes and humans. They used simple tools like sticks and other non-durable plant parts which were found in their immediate surroundings.

Homo habilis (The handy man)

The words Homo habilis is derived from Latin words Homo meaning human and habilis meaning handy or skillful. They were the first early true man to have lived on earth between 2.3 and 1.5 million years ago.

They had a height of about 1.5 metres and cranial capacity of 650-800 cc. The face was slightly protruding, had round skull and teeth with small canines. Brow ridges were present, and they had lightly built lower jaw.

H. habilis had an erect posture and bipedal locomotion. Since they were the first fossil man to have used chipped stone tools, H. habilis were also known as toolmaker.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Homo Erectus (The upright man)

Homo erectus lived between 1,00,000 and 1.6 million years back and were much larger than H. habilis, about 1.5-1.7 metres tall.

Homo erectus had bigger brain with cranial capacity of around 900 cc and showed structure of brain similar to that of modern humans. The bones of the skull were thick, and they had sloping forehead, flatter face, massive brow ridge, smaller chins and rounded jaw. Arms and legs were in proportion as in modern humans.

They had small canines but molar teeth had large roots. They were first hominid to use fire. H. erectus successfully hunted large animals using flint and bone tools and cooked them over fire.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Homo Sapiens Neanderthalensis

The Neanderthal man lived in Europe and east and central Asia between 40,000-1,00,000 years ago. Compared to modern humans, they were short and had robust skeletons with muscular bodies adapted for cold.

They had massive skulls with brain capacity of 1300-1600 cc and were 1.5 to 1.6 metres tall. They had protruding face, with thick but rounded brow ridge that lay under a flat and receding forehead. The mandible was strong and jaw lacked the projecting bony chin.

They had larger teeth than those of modern humans. The Neanderthal man lived in caves and built hut- like shelters. They were skilled hunters, made flint-flake tools, cared for their sick and buried their dead.

Homo sapiens fossilis (Cro-Magnon man)

The fossils of Cro-Magnon man were discovered from Cro-Magnon cave in France, hence its name. They lived 20,000-50,000 years back and become extinct about 10,000 years ago.

They were about 1.8 metres tall with less body hair. They had brain capacity of about 1650 cc. They had large skull, broad flat face with high forehead, strong jaws and wisdom teeth with teeth placed together, prominent chin and inconspicuous brow ridges.

They were cave-dwellers; good hunters, made sophisticated tools like stone spears and arrows, knew the use of fires and used ornaments made of ivory. They loved art paintings on cave walls. They domesticated animals.

Homo sapiens sapiens (Modern man)

The modern man appeared some 25,000 years back and spread all over the world about 10,000 years ago. They had undergone slight morpho anatomical changes, such as thinning of skull bones, development of four curves in the vertebral column and brain capacity of about 1200-1600 cc.

Face is reasonably small with a projecting nose, brow ridge is limited and tall forehead. The teeth are relatively small compared to earlier species. This is especially noticeable in the front incisors and canines.

Their jaws are smaller and less protruding. They have wider pelvis, S-shaped spine, angled femur and toe aligned. They have longer thumb and shorter fingers for tool use.

They underwent cultural evolution to adapt to and control surrounding environment. They started cultivating plants and domesticating animals.

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UP Board Notes For Class 10 Science Chapter 15 Human Evolution Theories Of Evolution

From time to time, several theories have been put forth to explain the process of evolution of the plants and animals. Some of these theories are described here.

Lamarck’s Theory of Inheritance of Acquired Characters

Jean Baptiste Lamarck (1744-1829) was a French evolutionist. He explained the principal behind evolutionary process in his book named Philosophie Zoologique. Lamarck stressed on adaptation as means of evolutionary modification. His theory is known as theory of inheritance of acquired characters or Lamarckism. The main features of his theory are:

1. Every living organism tends to increase volume of its body and hence increase size upto a certain limit.

2. The development of an organ is directly proportional to its use. The use and disuse of an organ by an organism leads to acquiring of variation or change in the feature of that organ. Continuous and extra use of an organ makes it more efficient while the continued disuse of other organs lead to their degeneration and ultimate disappearance. So, Lamarckism is also called theory of use and disuse of organs. This change occurs due to interaction with the environment.

During its life span, the organism acquires certain new characters due to the environmental influences and are called acquired or adaptative characters.

3. All these changes or variations (called acquired characters) acquired during the life of an individual are transmitted to its offspring, i.e. they are inherited (hence the name theory of inheritance of acquired characters).

4. The favourable variations caused due to use and disuse after long period of time result in evolution of a new species.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Examples To Support Lamarckism

1. Lamarck took the example of the giraffe in support of his theory.

a.According to Lamarck, there was a time when the giraffes were short-necked.

b.When this short-necked giraffe did not find any vegetation to feed on the ground, they tried to reach the upper part of a tree to eat its leaves.

c. Thus, by making continuous efforts, the neck and forelimbs of giraffe started becoming longer gradually.

d. These acquired characters were inherited by the offspring of the giraffe in successive generations.

e. After a considerable long period of time, the giraffe evolved having a long neck and longer forelimbs than hindlimbs.

This is an example of effect of extra use and elongation of certain organs.

2. Vestigial organs refer to the organ structures that have lost all or most of its original function present in another species, generally present in rudimentary conditions.

For example, vermiform appendix, an appendage of caecum, is believed to have been used by humans’ herbivorous ancestors to digest cellulose.

Wisdom teeth and pinnae (external parts of car in humans) are other examples of vestigial organs. These are some examples which are taken in support of disuse of organ.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Objections To Lamarck’s theory

Lamarck’s theory of inheritance of acquired characters was strongly criticized by August Weismann. He cut the tails of white mice for continuously 21 generations, however, their progeny did not show any cut tails. Thus, if the inheritance of acquired characters (i.e. cut tail in this case) was a fact then, the tailless mice should have born, which did not happen.

Darwin’s Theory of Natural Selection

Charles Robert Darwin (1809- 1882) explained the evolutionary principle in his famous book The Origin of Species in 1859. He described the origin of species by means of natural selection. His theory is known as Theory of natural selection or Darwinism.

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In 1831, Darwin went on a voyage of world exploration on a ship named HMS Beagle and studied the flora and fauna of South America, the Galapagos islands and other islands during his journey. He also studied the population theory of Malthus and then proposed his theory of natural selection. The main points of Darwin’s theory of natural selection are as follows:

1. Living beings have a biotic or reproductive potential and their number grows geometrically.

For example, Paramecium divides three times by binary fission in 24 hours under favourable conditions. At this rate, it can produce about 280 million clones in a month and in five years, it can produce Paramecia having mass equal to 10,000 times than size of the earth.

This will lead to numb of species which will be much more than what can be supported on earth.

2. Limited food and space together form major part of carrying capacity of environment, which is maintained by food chains and biogeochemical cycling. Despite having enormous potential of having large progenies, the size of population of any kind of organism remains within a limit.

This population size limitation is due to struggle between members of a species i.e.intraspecific struggle and within members of different species i.e. interspecific struggle for food, space and mate.

3. There is a competition amongst the organisms for obtaining resources. The struggle eliminates the unfit individuals. The fit organisms possess some favourable variations and they survive and reproduce. This is called natural selection.

For example, during drought, only those plants will survive which transpire less and are able to absorb water from deeper layers of soil.

4. The organisers having favourable variations reproduce and pass on these variations to their progenies generation after generation.

These variations, when accumulated for a long time, lead to origin of a new species.

Later on, with the progress in genetics, the sources of variations were explained and Darwin’s theory was modified. This modified theory is known as Synthetic theory of evolution and nowadays, it is the most acceptable theory of evolution. This theory states that the origin of species is based on the interaction of genetic variations and natural selection.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Example To Support The Theory Of Natural Selection

The case of the peppered moth in England is the most frequently discussed example of natural selection. This refers to an increase in the number of dark-coloured moths due to increased industrial pollution. This is also referred as industrial melanism.

  • There were two varieties of peppered moth, grey or light-coloured and dark-coloured. Before industrial revolution, dark-coloured moths were hardly known. The light-coloured species could easily blend with the lichen-covered trunks of trees while resting. Dark-coloured moths on the other hand, were easily picked up by the predatory birds.
  • But due to the increase in sulphur dioxide in air (because of industries), the lichens started to reduce on tree trunks, exposing darker bark which was further darkened by falling smoke particles.
  • Now, the light-coloured species became conspicuous and attracted its predators. While dark-coloured species had the advantage of protection.
  • Within a period of few years, the industrial or polluted areas saw that the dark species had almost replaced the light species. Through this, moth showed natural selection at work.

UP Board Notes For Class 10 Science Chapter 15 Human Evolution Objections To Darwin’s Theory

Although Darwin’s theory of natural selection got wide acceptance, however, it had certain drawbacks, such as it could not explain how variations arise. Darwinism could not explain the origin of new characters. Scientists also claim that natural selection explains the survival of fittest but could not explain the arrival of fittest.

The main differences between Lamarckism and Darwinism are given in Table.

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UP Board Notes For Class 10 Science Chapter 15 Human Evolution Human Evolution Summary

  • The evolution is defined as a naturally occurring slow, continuous and irreversible process of change.
  • Dryopithecus was more ape-like while Romapithecus was more man-like.
  • Australopithecus had cranial capacity of 400-600 cc, was able walk or run, had projecting brow ridges over eyes and small brain.
  • H. habilis had cranial capacity of 650-800 cc, having small canines and brow ridges were present.
  • H. Erectus had cranial capacity of 900 cc, massive brow ridges and small canines.
  • The Neanderthal man were short and robust with brain capacity of 1300-1600 cc, round brow ridges and lived in caves and hut-like shelters.
  • Cro-Magnon men were about 1.8 m tall with less body hair and cranial capacity of about 1650 cc.
  • Modern man had a brain capacity of 1200-1600 cc and developed four curves in vertebral column.
  • Lamarck proposed theory of inheritance of acquired characters also called Lamarckism.
  • Darwin proposed theory of natural selection, also called Darwinism.

UP Board Notes for Class 10 Science Chapter 16 Pollution

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UP Board Notes For Class 10 Science Chapter 16 Pollution Learning Objectives

After completing this chapter, you will be able to:

  • Define pollution and differentiate between pollution and pollutant;
  • Classify materials into biodegradable and non-biodegradable;
  • List various types f pollution – air, water, soil, radiation and noise;
  • Describe the sources, effects and control of air, water, soil, noise and radioactive pollution;
  • Explain the cause and effect of global warming, acid rain and ozone layer depletion;
  • Describe the effect f pollution on climate, environment, human health and other organisms and its abatement.

Environment (derived from the French word environ meaning to encircle or surround) can be defined as the physical and biological world where we live. We depend on our environment, both for our natural and technological needs.

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UP Board Notes For Class 10 Science Chapter 16 Pollution Environment has three major components.

1. Physical surroundings: These include the air that we breathe, the water that we drink and the soil (land) on which we live. The physical components together contain nutrients like oxygen, carbon dioxide, nitrogen, mineral salts, water and many other substances.
2. Living organisms: These constitute the biotic environment, that is, plants and animals including humans and microorganisms like bacteria and fungi.
3. Climatic factors or meteorological components: These constitute another part of the physical environment and include sunlight, temperature, rainfall, humidity, pressure, wind speed, etc.

Overpopulation, urbanization and industrialization have contributed in various ways in the deterioration of the environment. It has resulted in the depletion of natural resources and disturbance of the ecological balance. This general deterioration of the environment has resulted in environmental pollution.

UP Board Notes For Class 10 Science Chapter 16 Pollution And Pollutants

Pollution can be defined as an undesirable change in the physical, chemical and biological characteristics of our surroundings, which adversely affects the natural quality of the environment, human life and other living beings.

Pollution can be natural or man-made. The substances that cause such changes (pollution) are called pollutants.

Pollutants can be categorized as follows:

1. According to source: Natural sources such as volcanic ash, forest fire, dust from storm, pollen grains in air and decay of organic matter. Man-made sources such as water from industries, motor transport emissions, oil from furnaces, sewage waste, fertilizers and pesticides, etc.

2. According to biodegradability: Pollutants can be biodegradable and non-biodegradable depending on their degradation into simpler substances by biological agents.

Air pollution

Air pollution can be defined as the occurrence or addition of foreign particles, gases and other materials into the air, which adversely affect the biological communities (human beings, plants, and animals) and physical surroundings (roads, buildings).

The World Health Organization (WHO) has defined air pollution as befouling the air by human activities to such an extent, that it is sufficient to cause harmful effects on the health, vegetation and property.

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Sources of air pollution

There are two sources of air pollution – natural and man-made.

 Natural sources

  • Forest fires, ash from smoking volcanoes, dust from torm, decay of organic matter
  • Pollen grains floating in air

UP Board Notes For Class 10 Science Chapter 16 Pollution Man-made Sources

  • Transportation: Motor transport and internal combustion engines that burn petrol, diesel, kerosene, etc., which causes release of carbon monoxide, hydrocarbons and nitrogen oxides
  • Fuel combustion: Industrial plants and power stations using coal or crude oil
  • Burning of vegetable oils, kerosene and coal in households
  • Furnaces using coal, cow dung cakes, firewood, kerosene, etc.
  • Burning of garbage and dust from brick kilns

Air pollutants

The air pollutants may be grouped under two categories.

1. Particulate air pollutants: The particulate air pollutants include solid particles suspended in air, smoke, soot, aerosols, dust and mists. They also include dust of cement, brick kilns, glass, ceramics and aerosols. Particles given off in the manufacture of metal items, cotton dust from textile industries and even pollen grains are also particulate air pollutants.

2. Gaseous air pollutants: These include smoke given out from burning of coal, firewood, cow dung cakes, kerosene oil, etc. and also from cigarettes, Biri, cigars and other tobacco products. Some of the important air pollutants are discussed
below.

Carbon dioxide

Carbon dioxide is one of the natural gases present in the atmosphere and is used by plants for photosynthesis. It is chiefly produced during the combustion of fossil fuels in households, factories, power stations, etc. The increasing content of CO₂ in the atmosphere is likely to have the following effects.

  • A rise in atmospheric temperature due to greenhouse effect would cause a decrease in the precipitation and soil moisture content.
  • More CO₂ will dissolve in water and the water in the oceans would be more acidic. This will

 

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lead to reduced productivity of the marine ecosystem.

  • The rise in temperature due to more CO₂ would cause melting of continental and mountain glaciers, leading to flooding of coastal areas of some countries.

UP Board Notes For Class 10 Science Chapter 16 Pollution Greenhouse Effect

Atmospheric concentrations of carbon dioxide, water, ozone, methane, nitrous oxide and chlorofluorocarbons. are key role players in maintaining the global temperature. Collectively, these gases act somewhat like a pane of glass in a greenhouse.

These impede the escape of longer, infrared wavelengths (heat) from the earth into the space. Thus, heat builds up in the lower atmosphere. This is called greenhouse effect.

  • In greenhouse effect, the greenhouse gases such as CO₂ and methane, produced by burning of fossil fuel, agriculture and deforestation trap heat radiated from earth and lead to increase in the earth’s temperature.
  • Rays of sunlight penetrate the lower atmosphere and warm the earth’s surface.
  • The earth’s surface radiates heat (infrared wavelengths) to the lower atmosphere. But greenhouse gases and water vapour absorb these infrared wavelengths and reradiate a portion back towards the earth.

    Pollution-A-summary-of-the-energy-received-and-lost-from sunlight-3

 

  • As the concentration of greenhouse gases increases in the atmosphere, the surface temperature of the oceans rises, more water evaporates into the atmosphere, and the earth’s surface temperature also rises.

An increase in the temperature of the atmosphere might cause sea levels to rise. Temperature near the ocean surface would increase and make glaciers and the polar ice sheets melt faster. This would flood the low-lying coastal regions like Bangladesh, Lakshadweep and the Andaman and Nicobar islands.

Carbon monoxide

  • It is produced as a result of incomplete combustion of fossil fuels like coal, petroleum and wood charcoal. Automobiles using diesel and petroleum are the major sources of carbon monoxide.
  • Carbon monoxide is more dangerous than carbon dioxide. It is a poisonous gas leading to respiratory problems. When it reaches the blood stream, due to its high affinity for haemoglobin, it replaces oxygen, and reduces oxygen carrying capacity of the blood. It also causes giddiness, headache and heart disease. In much higher concentration it can also cause death.

Sulphur dioxide

It is produced by the burning of coal in powerhouses and automobiles. It is mainly absorbed by water and goes into the soil as sulphuric acid. It causes chlorosis and necrosis of vegetation, irritation in eyes, asthma and bronchitis. It is also responsible for discolouration and deterioration of buildings, fabrics, leather, etc. and causes acid rain.

UP Board Notes For Class 10 Science Chapter 16 Pollution Acid Rain

  • Emissions of sulphur dioxide and oxides of nitrogen from power stations, factories and motor vehicles cause the formation of sulphuric and nitric acids in rain clouds. If rain falls through polluted air, it picks up more of these gases and increases its acidity. This is called acid rain.
  • Effects of acid rain: Damage to plants: Acid rain causes progressive death of young shoots; leaves turn yellow and fall off; fine root structure is damaged; and the whole tree eventually dies.

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  • Damage to soil: Acid rainmay make the soil more acidic. damaged by acid rain It may cause mineral nutrients to be washed away. It may help to release toxic chemicals, such as aluminium and mercury into the soil. Thus, acid rain changes soil salinity, which make soil less fertile.
  • Damage to freshwater life: Fish may be killed when acidity releases aluminium into the water. This builds up as a layer of aluminium hydroxide in the gills of fishes.

Can acid rain be reduced?

There are several ways in which sulphur dioxide emissions can be reduced.

  • Coal can be crushed and washed before burning.
  • Oil can be treated to remove sulphur.
  • Cleaning systems can be fitted into chimneys to remove sulphur dioxide before it can be released. into the atmosphere.
  • Furnaces that burn fuel more effectively and produce less pollution can be used.
  • Vehicle exhausts can be fitted in vehicles, which remove pollutants from engine emissions.

Smog

Smog is a mixture of smoke, dust particles and small droplets of fog. Smog may cause necrosis and develop a white coating on the leaves (silvering) of plants. In human beings and animals, it may cause asthma and allergies.

Hydrocarbons

Hydrocarbons are produced due the to incomplete combustion of burnt fuel. The most prominent hydrocarbon in air is methane (CH₂). Hydrocarbon is a cause of smog and cause skin cancer, irritation in eyes and respiratory system.

Aerosol spray propellants

The suspended fine particles in the air are known as aerosols. It is a group of chemicals, which are released into the air with force in the form of vapour or fine mist. Aerosols contain chlorofluorocarbons (CFCs) and fluorocarbons which cause depletion of the ozone layer.

Oxides of nitrogen

A few oxides of nitrogen, such as nitric oxide (NO), nitrous oxide (N₂O) and nitrogen dioxide (NO₂) are important air pollutants. Oxides of nitrogen are produced by natural processes as well as released from thermal power stations, factories, automobiles and aircrafts (due to the burning of coal and petroleum). They reduce the oxygen carrying capacity of blood, may cause irritation in eyes and skin cancer in human beings.

Pesticides

Extensive use of pesticides pollute the environment as they are not biodegradable. For example, DDT that gradually accumulates in the cells and tissues of plants is harmful to animals as well as human beings.

Peroxyacetyl nitrate (PAN)

  • PAN is formed due to the photochemical reaction of nitrogen oxides and hydrocarbons. In human beings, it causes stinging of eyes, cough, headache, pulmonary congestion, haemorrhage, dry throat, breathing problems and early ageing of the lung tissues.
  • Air pollution from brick kilns Brick is one of the most important building materials in our country. Brick preparation consists of clay preparation, shaping, drying and firing operations. The burning of fuel for firing bricks results in the emissions of gaseous pollutants and ash into the atmosphere. Some of the air pollutants that are produced from brick kilns are:
  • carbon dioxide and sulphur dioxide due to the burning of coal and wood.
  • Suspended Particulate Matter (SPM) generated due to the incomplete combustion of fuel or released from fine coal dust and ash,
  • hydrocarbons and carbon monoxide due to incomplete combustion of fuel.
  • dust and fly ash.

These pollutants causes irritation of skin and eyes, and their inhalation causes pulmonary diseases such as silicosis. Pollution due to brick kilns also affects agricultural crops and fruit plantations.

UP Board Notes For Class 10 Science Chapter 16 Pollution Effects Of Air Pollution On Human Health

  • Carbon monoxide combines with the haemoglobin molecules in human blood and causes suffocation.
  • Depletion of ozone layer due to CFCs causes skin cancer as a result of over exposure of the human skin to UV rays.
  • Sulphur dioxide originated smog blocks the human respiratory system leading to the death of the sufferer.
  • Sulphur dioxide pollution also causes diseases of the eyes, throat, nose and lung infections.
  • Sulphur dioxide pollution also causes acid rain, which pollutes the water, and thus, affects the health of persons consuming such polluted water.
  • Nitric oxide (NO) in high concentration causes respiratory problems, gum inflammation, internal bleeding, oxygen deficiency, pneumonia and lung cancer.
  • Air pollutants like SPM cause asthma, lung cancer and asbestosis.
  • Some pesticides like DDT (Dichloro-diphenyl- trichloro ethane) are very toxic. When these pesticides enter our food chain and accumulate in our body (a process known as biomagnification), cause kidney disorders and brain and circulatory system-related disorders.
  • Sudden leakage of poisonous gases from factories and chemical plants kills hundreds of people and livestock. The Bhopal gas tragedy of December 1984 is a burning example of such a deadly disaster. The leakage of methyl isocyanate (MIC) gas from the Union Carbide factory claimed thousands of animal and human lives in Bhopal.

Table summarizes the sources and effects of some major air pollutants on human health.

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UP Board Notes For Class 10 Science Chapter 16 Pollution Occupational Hazards

There are many diseases that are related to our occupation. These diseases are known as occupational hazards. Some of these diseases are given below.

  • Silicosis or Silicotuberculosis: This disease is caused due to the inhalation of free silica or silicon dioxide (SiO₂) while working in industries related to pottery, ceramic, glass, mining, building and construction work. The persons suffering from these diseases get chronic coughs and pain in the chest.
  • Byssinosis: This disease occurs due to the inhalation of cotton fibres over a long period of time. The person suffering from this disease experiences chronic cough and chronic bronchitis.
  • Asbestosis: This disease is caused due to inhaling asbestos powder used in making ceilings. Asbestos also causes cancer.

UP Board Notes For Class 10 Science Chapter 16 Pollution Effects Of Air Pollution On weather And Climate

  • Depletion of ozone layer caused by CFCs may change the radiation balance at global level. This may result in an increase in the UV radiation reaching the earth’s surface and, therefore, could lead to a rise in the air temperature (global warming). Global warming would cause melting of continental glaciers and ice caps. This would cause a rise in the sea level and consequent submergence of coastal lands and lowland countries.
  • Increase in the concentration of CO₂ and other Ozone layer depletion What are the ill effects of ozone layer depletion? greenhouse gases would cause greenhouse effect. This would lead to an increase in temperature and result in climatic changes.
  • When smog is mixed with air pollutants causes deadly health hazards to humans, low visibility and increased road accidents.
  • Acid rain due to SO₂ destroys and defaces buildings, sculptures and monuments resulting in damage to property and national heritage.

UP Board Notes For Class 10 Science Chapter 16 Pollution Methods of Controlling Air Pollutants

  • Combustion: This technique is used for controlling those air pollutants that are in the form of organic gases or vapour. In this technique, organic pollutants are converted into less harmful products such as CO₂ and water vapour.
  • Absorption: In this technique, gaseous pollutants are passed through absorbing material like scrubbers. These scrubbers contain a liquid absorbent. This absorbent modifies or removes one or more of the pollutants present in gaseous effluents. Thus, the air coming into scrubber become free from pollutants and it is then discharged into atmosphere.
  • Adsorption: In this technique, gaseous effluents are passed through porous solid adsorbent kept in suitable containers. The gaseous pollutants either stick or get adsorbed at the surface of the porous material and clean air passes through. The organic and inorganic constituents of gaseous effluents

UP Board Notes For Class 10 Science Chapter 16 Pollution Ozone Layer Depletion

What are the ill effects of ozone layer depletion?

Ill effects of ozone layer depletion are:

At ground level, ozone is a harmful pollutant that damages plants and building materials and is hazardous to human health. However, in the upper atmosphere, ozone is like a life cover that protects us by screening the dangerous ultraviolet (UV) rays of the sun.

Without the ozone layer shield, the organisms on the earth would be subjected to life-threatening radiation burns and genetic diseases. Do you know that a 1% loss of ozone in the stratosphere results in a 2% increase in UV rays reaching the earth’s surface.

This could result in about one million times increase in the human skin cancer worldwide if protective measures are not taken.

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What causes ozone layer depletion?

Causes ozone layer depletion are:

The exceptionally cold temperature (-85 °C to -90 °C) in Antarctica plays a role in ozone layer depletion. Ozone and chlorine- containing molecules are absorbed on the surface of ice crystals at high altitudes in Antarctica.

In the presence of sun’s rays, these chlorine ions are liberated and destructive chemical reactions take place. We also release a variety of chlorine-containing molecules into the atmosphere.

The most important for ozone depletion are CFCS and halogen gases. CFCs are very stable molecules, thus, they persist for decades, even centuries, once released. When they diffuse into the atmosphere, the intense UV irradiation releases chlorine atoms that destroy ozone.

International Ozone Day is held on 16 September every year. are trapped at the interface of solid adsorbent by physical adsorption.

UP Board Notes For Class 10 Science Chapter 16 Pollution Methods to Control Particulate Air Pollutants

The particulate air pollutants such as dust, soot, fly ash, etc., can be controlled by using fabric filters, electrostatic precipitators, wet scrubbers and mechanical devices, etc. These are given below.

  • Mechanical devices: The mechanical devices work either by gravity in which the particle settle down by gravitational force, or by sudden change in the direction of gas flow in which particles separate out due to greater momentum.
  • Fabric filters: In this technique, gaseous emission containing dust, soot and fly ash is passed through porous fabric filters made of fabric (woven or filled fabric). The particles of pollutants present in the gas get trapped in this fabric and are collected in the filter and the gases free from the pollutant particles are discharged.
  • Wet scrubbers: The wet scrubbers are used in chemical, metallurgical and mining industries. The wet scrubbers trap SO₂, NH3 and metal fumes in their tank and clean gases are discharged in the atmosphere.
  • Electrostatic precipitators: An electrostatic precipitator is a device containing a chamber that induces an electric charge on the particles of polluted air. These particles are then attracted to the oppositely charged electrode and are deposited there. In this technique, a gas or air steam containing aerosols in the form of dust, mist or fumes, is passed between the two electrodes of the electrostatic precipitator. During this process, the aerosol particles get precipitated on the electrode.

In addition to this, air pollution may also be prevented and controlled by the following measures.

  • Using better-designed equipment and smokeless fuels/hearths in industries and at home.
  • Using environment-friendly fuels, such as compressed natural gas (CNG) in automobiles instead of petrol/diesel.

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  • Locating industries discharging heavy smoke and toxic fumes at places far away from human habitation.
  • Planting more and more trees surrounding industrial establishments, along the roadside and in residential areas to reduce CO₂ level in the environment.
  • Strictly adhering to emission-control standards for automobiles – BS-IV norms.
  • Harnessing renewable energy resources, such as wind, solar energy and ocean currents, and minimizing the use of fossil fuels.

Euro-Bharat vehicular standards Euro-Bharat vehicular standards are instituted by the government of our country which regulates the output of air pollutants such as nitrogen oxides, carbon monoxide, hydrocarbon, particulate matter, soot and sulphur dioxide by motor vehicles.

In many cases they are similar to European emission standards, (Bharat Stage 1 equivalent to Euro I, BS II: Euro II, BS III: Euro III and BS IV: Euro IV). Since 1 April 2017, the Supreme Court of India has banned the sale of BS-III vehicles and BS-IV norms are now applicable across our country.

UP Board Notes For Class 10 Science Chapter 16 Pollution Water Pollution

Water pollution can be defined as a change in physical, chemical and biological properties of water by the addition of undesirable substances which may have harmful effects on human and aquatic life.

 

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Sources of water pollution

Water pollution occurs due to its two sources –

1. Point sources: These sources discharge water pollutants directly into the water. For example, factories, power plants, underground coal mines,

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oil wells situated near water bodies, etc., are point sources of water pollution.

2. Non-point sources: These sources do not have any specific location for discharging pollutants in the water body. For example, run offs from field, lawns, gardens, construction sites, water-logged areas, roads and streets are some non-point sources of water pollution.

Pollution of freshwater

Freshwater is naturally occurring water on the earth’s surface in ponds, rivers, lakes and streams, and groundwater in underground streams. Freshwater has salt concentration of less than 1% and hence is not saline.

Pollution of freshwater is contamination by substances that make it unfit for natural or intended use such as drinking and washing purposes. Freshwater may be polluted in many ways, which are described as follows.

  • Domestic sewage discharged into rivers without treatment. Phosphate and nitrate ions from excretory wastes of humans and animals pollute the water. This may cause diseases like typhoid, cholera, dysentery, etc., in the persons drinking such water.
  • Organic wastes from agricultural fields along with phosphate and nitrogen fertilizers that reach lakes, rivers and sea (water becomes deoxygenated and poisonous, thus, cannot support aquatic life).
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  •  Industrial wastes (effluents) from urban areas contain high concentrations of oil, heavy metals, synthetic detergents and alkalis.
  • Pesticides, insecticides such as DDT and some industrial wastes containing mercury pollute the water and reach the food chain and ultimately in humans, affecting aquatic and human health.

UP Board Notes For Class 10 Science Chapter 16 Pollution Industrial Discharge

Industrial wastes contain harmful chemicals, oils, heavy metals, radioactive wastes and suspended solids which when discharged into water, make it poisonous. Since it is difficult to breakdown wastes, they affect the quality of water and pollute it.

Detergents

Inorganic pollutants like synthetic detergents, acids, salts and toxic metals contain compounds that make the water unfit for use and pollute it. Detergents primarily omprise phosphate, thereby increasing the phosphate levels in water, thus making it unfit for use.

UP Board Notes For Class 10 Science Chapter 16 Pollution Thermal Pollutants

Thermal pollution is the degradation of water quality by any process that changes the temperature of water. Thermal pollution is caused by the water which is used as a coolant by power plants, nuclear power plants and industries.

When this water (after cooling) returns to the natural streams, it is at a very high temperature, making it inappropriate for use. The change in temperature decreases oxygen supply, making it unfit for flora and fauna to survive. It also results in the growth of algae.

Radioactive pollutants

Radioactive materials enter the water through nuclear power plants, due to conducting nuclear tests and spillage from industries, and through mining of radioactive elements.

When radioactive substances enter the water bodies, especially seawater and oceans, they cause severe damage to the marine ecosystems and even cause gene mutation and other human diseases.

Marine pollution

Marine pollution is the contamination of oceans and seawater. The oceans and seawater mostly get polluted due to sewage, industrial waste, radioactive waste and oil spills.

UP Board Notes For Class 10 Science Chapter 16 Pollution Oil Spills

Oil pollution of oceans and rivers is caused due to spillage of oils from oil tankers, accidental spillage, refineries, offshore drilling and cleaning of fuel tanks of ships. On discharge, oil spreads on water and forms a layer of oil (oil slick). This is very harmful to aquatic life including fish, mammals and marine birds.

Effects of water pollution

  • The presence of acids and alkalis in water destroys microorganisms, thereby hindering the self-purification process in rivers.
  • Water pollution adversely affects aquatic life.
  • The toxic materials may enter the food chain and cause serious health hazards in human beings and other aquatic animals.
  • Polluted water causes epidemics, such as cholera, tuberculosis, jaundice, dysentery, typhoid and diarrhoea in human beings.
  • The use of polluted water from lakes, ponds and rivers for irrigation of agricultural fields damages crops and decreases the agricultural production.
  • Heavily polluted water affects the soil, decreases its fertility and kills soil microorganisms and even certain useful bacteria.
  • The use of water contaminated with salts increases the alkalinity of the soil.
  • Contamination of seawater due to oil slicks caused by the leakage of crude oil from oil tankers results in the death of sea organisms including fishes.

Prevention and control of water pollution

Some steps to reduce water pollution are listed below.

  • Setting up sewage water treatment plants before its disposal into rivers.
  • Using septic tanks in houses to avoid direct outlet of faecal matter and other wastes.
  • Avoiding contamination of rivers, lakes and ponds by washing clothes, bathing, etc.
  • Not throwing waste food materials, paper, biodegradable vegetables and plastic into open drains.
  • Diverting effluents from distilleries and solid waste containing organic matter to biogas plants to generate energy.
  • Treating industrial effluents before discharging into rivers, separate channels for river and sewage water.
  • Totally baning on nuclear waste dumping in water.
  • Generating public awareness about the maintenance of ponds, river, lakes and wells in rural and urban areas.
  • Disposing of safely biomedical wastes like needles, syringes, soiled dressings, etc.

UP Board Notes For Class 10 Science Chapter 16 Pollution Soil Pollution

Any substance that reduces the productivity of soil is known as soil pollutant and the process, as soil pollution.

Causes of soil pollution

Soil pollution (also known as land pollution) is mainly caused due to the following reasons:

  • Solid wastes (farm and animal manure)
  • Agricultural wastes like plant remains, fertilizers, pesticides and other chemicals.
  • Dead animal carcasses
  • Industrial waste chemicals like fly ash and residues of combustion of solid fuels.
  • Domestic garbage, paper pulp, plastic, rubber, cloth, leather, metal scrap and glass.
  • Biomedical wastes such as used syringes, cotton pads, needles, dirty dressings and discarded biological research materials. When disposed of in the garbage pollutes soil and affects soil organisms.

Prevention and control of soil pollution

  • Effluents from industries and factories should not be allowed to enter the soil indiscriminately.
  • Drainage system should be so developed that the polluted water does not get mixed up with the soil.
  • Proper toilet facilities should be provided to all and awareness should be created about the harmful effects of defecation in open places.
  • Fertilizers, pesticides and insecticides should be used judiciously so that excess chemicals are not washed into the soil.
  • Safe methods of disposal of domestic, agricultural and industrial solid wastes should be adopted.

UP Board Notes For Class 10 Science Chapter 16 Pollution Of Waste Materials Biodegradable And Non-biodegradable

We produce various kinds of waste materials due to our day-to-day activities. The waste materials can be broadly classified into two types – biodegradable wastematerials and non-biodegradable waste materials.

Pollution-Biodegradable-and-non-biodegradable-wastes-11

Biodegradable waste materials

  • The waste materials that can be broken down or decomposed into simple substances in nature, by the action of microorganisms, such as bacteria, in due course of time are called biodegradable waste materials.
  • The biodegradable waste decomposes naturally and becomes harmless to humans, and other environments after some time. For example, dead plants and animals (including bones), animal excreta (cattle dung, urine), leather goods, tea leaves, wool, paper, plant parts, hay and wood, cotton clothes, cardboard, seeds, grains and compost (manure made from decayed plants and vegetable stuff) are all biodegradable materials.
  • For example, plastic, polythene bags, synthetic fibres, glass objects, metal articles like aluminium cans, silver foils, certain detergents, fertilizers, pesticides like DDT and radioactive wastes. For instance, DDT is a non-biodegradable waste. It cannot be degraded or decomposed into simple compounds by the action of microorganisms in nature. Thus, it gets accumulated in the environment and harms humans, other animals, and even vegetables and plants. Thus, DDT has been banned for use in most of the countries.
  • gives a summary of the main differences between biodegradable and biodegradable wastes.

Recycling of biodegradable wastes

Some of the biodegradable wastes can be recycled to restore our natural resources and ecological balance. We may again use the products of recycled materials for our day-to-day activities.

Pollution-Difference-between-biodegradable-and-non-biodegradable -wastes-12

UP Board Notes For Class 10 Science Chapter 16 Pollution Noise Pollution

Noise pollution can be defined as unwanted or offensive sounds that unreasonably affect our daily activities. The term noise is very subjective. Sometimes when you are concentrating on your work then even a mild conversation or whisper sound may become a noise.

On the other hand, if you are in light mood in a party, then even many people talking does not seem to be noise.

The unit of sound intensity measurement is decibel (dB). Decibel is the unit for measuring the relative loudness of sounds that human ears can normally detect.

Major sources of noise pollution

  • Road traffic: Road traffic noise one of the most widespread and growing environmental problems.
  • Air and rail traffic: In areas close to the airports and railway tracks, the sound of aeroplanes and trains are major sources of noise pollution.
  • Neighbourhood and domestic noise: Barking dogs, car horns, loud music, TVs, loudspeakers, construction and household noise are some of the major sources of noise pollution.
  • Noise from industries: At many places, industries are located in close proximity of the residential areas or within the residential areas. Sound of machines, etc., causes noise pollution.

Harmful effects of noise pollution

  • Noise can affect human health and well-being in a number of ways, including annoyance reaction, sleep disturbance, interference with communication, performance effects, effects on social behaviour and hearing loss.
  • Noise can cause annoyance and frustration as a result of interference, interruption and distraction.
  • People experiencing high noise levels have increased incidences of headaches, greater susceptibility to minor accidents, increased reliance on sedatives and sleeping pills, and increased mental sickness.
  • Exposure to noise is also associated with a range of possible physical effects including cold, changes in blood pressure, other cardiovascular changes,
  • problems with the digestive system and general fatigue. Prolonged exposure to noise levels at or above 80 dB can cause deafness because of the damage to the organ of Corti in the internal ear.

How to control noise pollution?

The noise pollution can be minimized in following ways.

  • Reduce the noise at its source in industries and automobiles, etc.
  • Try not to put the TV on high volume. When playing music, turn it down at a reasonable level. Better use headphones if you want to play your music loud or late at night.
  • Plant trees at roadsides; put curtains on the doors and windows; instal glass panes at the windows, etc., to interrupt the path of the noise. This will reduce the noise to some extent.
  • Do not unnecessarily blow horns. This disturbs others.
  • If the source of noise is unavoidable cover your ears by hands or use ear plugs to avoid noise.

UP Board Notes For Class 10 Science Chapter 16 Pollution due To Radiation

The radioactive substances are generated due to nuclear activities in nuclear reactors and nuclear power plants. The radiations from these radioactive substances harm human health and health of other flora and fauna. There are three types of radiations generated from nuclear activities.

1. Alpha particles that cannot penetrate human skin or a sheet of paper.
2. Gamma rays usually produced from cobalt source, which can penetrate human skin and harm body cells. Gamma rays are most harmful to human beings.
3. Beta rays that can penetrate skin but not glass and metal.

The source of radiation pollution are nuclear reactors, X-rays, nuclear power plants, radioisotopes,gamma chambers, radioactive ore mining.

Effects of radiation pollution

There are many effects of radiation pollution which may be short-term and long-term. The short-term effect may be skin burns and skin cancer. The long-term effect of radiation include gene damage by mutation in genes; and cancer of intestine, bone marrow, gonads and spleen. Radiation can also cause loss of immunity, loss of hair and chromosomal abnormalities.

UP Board Notes For Class 10 Science Chapter 16 Pollution Swachh Bharat Abhiyan -A mass Movement To Clean India

  • Swachh Bharat Abhiyan is a campaign launched by the government of India to make India a clean and green country. It was officially launched by the Prime Minister of India on 2 October 2014 at Rajghat, New Delhi.
  • It is India’s largest ever cleanlisness drive. One of the key objectives of Swachh Bharat Abhiyan is to reduce or eliminate open defecation by constructing toilets. The government’s objective was to make an Open Defecation Free (ODF) India by 2 October 2019, by constructing 12 million toilets in rural India.
    The government has allocated special budget for Swachh Bharat Abhiyan. The railways is also planning to have facility of clean bed-rolls from automatic laundries, and bio-toilets etc., under this Abhiyan. The government has nominated key social personalities as ambassadors for this Abhiyan.

Swachh Survekshan

With an aim to foster a spirit of competition among the cities on cleanliness and assess their sanitation status, the government of India has started ranking cities on the basis of cleanliness surveys known as Swachh Survekshan. The performance of each city is evaluated on key parameters like

  • sweeping, collection and disposal of wastes.
  • open defecation free / availability of toilets.
  • capacity building and e-learning. provision for public and community toilets.
  • information dissemination and behavioural change. As per Swachh Survekshan 2017,
  • Indore, Madhya Pradesh was ranked the top city on cleanliness. indicators.

 

Pollution-biodegradable-and-non-biodegradable-wastes-collectionstes

UP Board Notes For Class 10 Science Chapter 16 Pollution Summary

  • An undesirable change in the physical, chemical and biological characteristics of our surroundings which harms the human life and other living beings is known
    as pollution.
  • Air pollution may be defined as the occurrence of foreign particles, gases and other materials in air, which have adverse effects on biological communities and physical surroundings.
  • Carbon monoxide, carbon dioxide, sulphur dioxide, fluorides, smog, aerosol spray propellants, oxides of nitrogen, suspended particulate matter, pesticides, and peroxyacetyl nitrate (PAN) are some common air pollutants.
  • Water may be polluted by pesticides, chemicals, industrial and domestic wastes, mineral and organic wastes, and radiation wastes.
  • Solid and agricultural wastes, dead animals’ carcasses, industrial wastes and domestic garbage cause soil pollution.
  • The waste materials that can be broken down or decomposed into non-poisonous substances by the action of microorganisms are called biodegradable materials.
  • The materials that cannot be decomposed to non-poisonous substances in nature by the action of microorganisms are called non-biodegradable waste materials.
  • Unwanted or offensive sound that unreasonably affects our daily activities is called noise pollution.
  • Radiations from radioactive substances cause radiation pollution.

UP Board Notes Class 10 Science Chapter 12 Endocrine System and Adolescence

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UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Learning objectives

After completing this chapter, you will be able to:

  • Discuss the role of endocrine system in maintaining homeostasis;ZZ
  • Define the term hormone;
  • Describe the location of the major endocrine glands in the human body,
  • List the major hormones secreted by the following endocrine glands and discuss their functions:
  • Adrenal gland
  • pancreas
  • Thyroid gland
  • pituitary glan
  • Explain the effects of hyposecretion and hypersecretion of major hormones on the body;
  • Describe the mechanism of hormonal action and regulation or the feedback mechanism.
  • All organs, tissues, and cells in our body work in coordination. There are two regulatory systems involved in control and coordination of our body, namely, nervous system and endocrine system.
  • In the previous chapters, you have read about nervous system and the functions performed by it. There is one more system involved in coordinatingEndocrine-system-Differences-between-the-functioning-of the-endocrine-system-and-the-nervous-system 1

various body activities. This is known as the endocrine system. The endocrine system affects body activities by releasing chemical messengers, called hormones, into the bloodstream. The endocrine system consists of many glands; however, in this chapter, we will learn about adrenal, pancreas, thyroid, and pituitary glands only.

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Adjusting To Changes – Homeostasis

  • The activities in our body occur in a coordinated manner and have to be regulated at a proper time. If any step in the coordination misses out, then our body is severely affected.
  • Let us consider an example to understand this. We tend to sweat a lot on a hot day. Evaporation of the  sweat cools down our body and helps to cope with the heat. We feel thirsty and drink more fluids on a hot day. Thus, our internal system adjusts itself to cope with the external stress and attempts to maintain a steady state of functioning.

The capacity of an organism to adjust itself to cope with the external changes and maintain a steady state of functioning is called homeostasis.

In our body, homeostasis is achieved by both the nervous and the endocrine systems, but in different ways, as given in

Endocrine-system-Differences-between-nervous-control-and-hormonal-control 2

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence What Are Hormones?

Hormones:

  • Hormone means to set in motion or to spur on. Hormones are chemical secretions secreted by specific endocrine glands, which are carried by blood to the target organs elsewhere in the body to stimulate a specific activity. Thus, hormones are special chemicals that regulate the physiological or biochemical processes in our body.

Bayliss and Starling, two British scientists, coined the term hormone in 1905 while working on hormonal secretions.

Characteristics of Hormones

  • Hormones are regulatory chemicals that are secreted by endocrine glands directly into the blood.
  • Some hormones are chemically made of proteins or polypeptides (e.g. insulin) which are water soluble;

Endocrine and Exocrine Glands

Hormones are secreted by endocrine glands (Gk. endo: within or inside; crin: secretion). These are also called ductless glands because they do not have their own ducts, and their secretions are directly released into the tissue space next to them from where these are carried by the blood to the target organ. On the other hand, an exocrine gland secretes material directly into the duct. They have their own ducts which carry the secretions directly to the target organs.

 

Endocrine-system-glands-with-and-without-ducts

a. An endocrine gland secretes hormones into the extracellular fluld.

b. An exocrine gland secretes material into a duct.

some are amines (e.g. adrenaline and noradrenaline) which are also water-soluble, and some are steroids which are derived from cholesterol, and other steroids (e.g. testosterone and progesterone) which are lipid-soluble.

  • Hormones are produced in very minute quantities.
  • They are biologically very active but are slower than nervous control.
  • They act only on target organs or cells located away from their sources. Thus, they are produced by one organ but act on some other organ.
  • They regulate the physiological process of the body by bringing about chemical changes. Thus, they bring about metabolic regulation in the body.
  • They are destroyed soon after their action, and thus, they are not stored in the body.
  • Steroid hormones They are steroids In nature. They diffuse through the cell membrane and bind to Internal receptors. Examples: Oestrogen, progesterone, androgens, cortisol, aldosterone, thyroid hormones, etc.
  • Peptide or non-steroidal hormones These are amino acid derivatives, peptides, or proteins. They bind to receptors located on the surface of target cell. Examples: Glucagons, ADH, oxytocin, Insulin, somatotropin, prolactin, FSH, LH, TSH, etc.

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Endocrine Glands

Major endocrine glands in our body are as follows:

1. Adrenal glands
2. Thyroid gland
3. Pancreas (pancreatic islets clusters)
4. Pituitary gland (anterior and posterior)
5. Parathyroid glands (four in humans)
6. Thymus gland
7. Pineal gland
8. Gonads

In addition, endocrine cells of stomach, duodenum, liver, kidney, placenta, etc. also secrete hormones.

Endocrine-system-Location-of-endocrine-glands-in-our-body-4


In this chapter, we will study about thyroid, adrenal, pancreas, and pituitary glands only. Location of various endocrine glands and their secretions are given in

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Adrenal Glands

In our body, two adrenal glands are present, one on top of each kidney; hence, they are also called suprarenal glands. Each adrenal gland has following two parts:

1. Adrenal cortex (on the outer periphery)
2. Adrenal medulla (inside central part)

 

Endocrine-system-Position-of-adrenal-glands-on-kidney

a. Kidney

b.Cross section of adrenal gland

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Adrenal cortex

Adrenal cortex secretes two main hormones – glucocorticoids and mineralocorticoids.

Endocrine System Glucocorticoids

Glucocorticoids are group of hormones such as cortisol, corticosterone, and cortisone. Of the three, cortisol is the major hormone. Glucocorticoids,

  • Regulate the metabolism of proteins, fats (lipids), and carbohydrates in the body;
  • Regulate the blood sugar level and ensure energy supply to the body;
  • Adapt the body to external stress such as severe heat or cold, infections and burns, etc.

Apart from these, certain cortical hormones act as sex hormones causing premature sexual maturity in children.

  • Hyposecretion of glucocorticoids causes Addison’s disease. person suffers from mental lethargy, nausea and vomiting, weight loss, and muscular weakness. Hypersecretion of glucocorticoids causes Cushing’s syndrome. In this condition, person becomes obese, has high blood sugar levels, osteoporosis, weakness, and salt and water retention.

Mineralocorticoids (Aldosterone)

Aldosterone is a major mineralocorticoid secreted by adrenal cortex. Aldosterone,

  • Controls mineral metabolism by reabsorption of sodium in urinary tubules and maintains Na* and K* ratio in the extracellular and intracellular fluids;
  • Regulates salt-water balance in the body.

Hypersecretion of aldosterone causes  increased sodium and decreased potassium concentration in the blood, leading to hypertension (high blood pressure).

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Adrenal Medulla

  • Adrenal medulla secretes two major hormones – adrenalin (also known as epinephrine) and nor-adrenalin (norepinephrine). Adrenalin accounts for almost 80 percent of the total secretion of the adrenal medulla.
  • Both adrenalin and noradrenalin together control emotions, fear, anger, blood pressure, heartbeat, respiration, and relaxation of smooth muscles. Adrenalin is also known as an emergency hormone as it prepares the body for fight-or-flight situations.
  • Adrenalin increases heartbeat and blood supply to muscles and decreases blood supply to visceral organs. We have high levels of adrenalin while playing or running. Effect of adrenalin on some organs of our body is given in

Endocrine-system-Effect-of-adrenaline-on-some-body-organs-6

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Thyroid Gland

The thyroid gland is a large endocrine gland located in front of the neck region just below the larynx. It has two lateral lobes, one on either side of the trachea. The two lobes are connected by a narrow mass of tissue called isthmus. The thyroid gland has a rich blood supply. Thus, thyroid gland can deliver large amounts of hormones in a short period of time, if necessary. Four small round parathyroid glands are embedded in the posterior surface of the thyroid gland.

 

 

Endocrine-system-the-thyroid-gland-is-ocated-in-neck

a. Anterior suface

b. posterior surface

The thyroid gland secretes two hormones thyroxine and calcitonin.

a. Thyroxine

  • It regulates basal metabolism by stimulating rate of cellular oxidation, resulting in energy production and maintenance of body temperature.
  • It regulates general growth of the body, ossification of bones, and mental development.
  • It regulates activities of the nervous system. Undersecretion (hyposecretion) as well as
    oversecretion (hypersecretion) of thyroxine result in an abnormal growth of the body.

Undersecretion of thyroxine (Hypothyroidism)

Undersecretion of thyroxine may cause,

1. Simple goiter: In this condition, the thyroid. gland of adults enlarges and becomes visible as a swelling in the neck. Undersecretion of thyroxine or insufficient amount of iodine in diet may cause simple goiter.

Endocrine-system-Enlargement-of-neck-region-due to-simple-goiter-8

Simple goiter is common in people living in hilly areas because the soil of hilly areas is deficient in iodine. Thus, the food crops grown there have less iodine content.

2. Cretinism (in children): This is caused due to defective development or early atrophy
(degeneration) of thyroid gland. This condition is observed in children. Children suffering from cretinism have stunted growth (dwarfism), short club-like fingers, and deformed bones and teeth. Their abdomen becomes pot-bellied, and skin becomes rough, dry with scanty hair growth. Mental retardation f various degrees is also observed.

3. Myxoedema (in adults): The hypothyroidism in adults causes myxoedema. In this condition, facial tissues swell and look puffy. Other symptoms include slow heart rate, low body temperature, sensitivity to cold, dry hair and skin, muscular weakness and general lethargy.

Endocrine-system-Aperson-suffering-from-myxoedema-9

Oversecretion of thyroxine (hyperthyroidism)

Oversecretion of thyroxine may cause exophthalmic goitre. A person suffering from this disorder shows increased metabolic rate, rapid heartbeat, protruding eyes and short breathing rate.

b. Calcitonin (Not included in the syllabus)

Calcitonin is another hormone secreted by thyroid gland.

  • It regulates calcium and phosphate levels in the blood.
  • It facilitates absorption of calcium released by bones.

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Endocrine System Pancreas

Pancreas is a compound gland located posterior to the stomach and attached to the duodenal loop in the abdominal region. It secretes both enzymes (digestive juices) as well as hormones. It has two parts –

1. An exocrine (duct) part, which produces digestive juices, and
2. An endocrine (ductless) part, which secretes hormones.

Endocrine-system-Exocrine-and-endocrine-portions-of-the -pancreas-10

Its endocrine part contains hormone-secreting cells called islets of Langerhans, which are scattered in the entire gland (islets: little islands). The islets of Langerhans in pancreas contain alpha, beta and delta cells that secrete glucagon, insulin and somatostatin hormones, respectively.

Insulin

Insulin is secreted by beta cells of islets of Langerhans.

  • It regulates blood sugar level by regulating conversion of glucose into glycogen. Whenever there is an increase in blood glucose, insulin is secreted which induces absorption of glucose through cells. This glucose is burnt or stored as glycogen. This reduces the blood glucose level.
  • It stimulates deposition of extra glucose as glycogen in the liver and muscles.
  • Undersecretion (hyposecretion) of insulin causes diabetes mellitus or hyperglycemia. A person suffering from diabetes mellitus has high concentration of glucose in the blood and urine. The sufferer feels thirsty because of loss of water through excessive urination and becomes weak.
  • Oversecretion (hypersecretion) of insulin causes insulin shock or hypoglycemia. In this condition, sugar level in bloodis severely reduced and in adverse condition brain may enter into a state of coma. The person may also becom onscious at frequent intervals.

Why is Insulin Injected and Not Taken Orally?

When required, insulin is injected into the body, and not taken orally because if taken orally, it will be digested by the protein-digesting enzymes in the digestive tract.

Glucagon

Glucagon is secreted by alpha cells of islets of Langerhans.

  • It stimulates glycogen breakdown in the liver and converts some carbohydrates back to glucose.
  • It increases sugar level in the blood.

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Pituitary – the Master Gland

  • The pituitary is a small gland about 1 cm in diameter (about size of a pea). It lies just below the hypothalamus (the midbrain) connected to it by a stalk-like structure called hypophyseal stalk.
  • It is popularly known as master gland because it controls the functioning of all other endocrine glands. Since most hormones secreted by pituitary stimulate other glands to produce their hormones, they are called tropic hormones. Thus tropic

Endocrine-system-The-pituitary-gland-11

  • hormones are those hormones that stimulate other endocrine glands to secrete their own specific hormones. For example, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are also called gonadotropic hormones because they regulate functioning of gonads (ovaries and testes) to produce sex hormones.
  • Except for human growth hormone, melanocyte-stimulating hormone (MSH), and prolactin (PRL), all the other hormones are tropic hormones.

The pituitary is mainly divided into three lobes.

1. The anterior lobe
2. The posterior lobe
3. The intermediate lobe (almost absent in humans)

Hormones of the anterior pituitary

The anterior pituitary releases at least six different hormones some of which are as follows.

1. Growth hormone (GH) or somatotropic hormone (STH) or somatotropin

  • It controls the overall development or growth of the body, muscles and bones.
  • It also stimulates fat metabolism.
  • It increases the rate of protein synthesis.
  • Deficiency (hyposecretion) of GH in the childhood causes dwarfism. In this condition, the muscles and skeleton do not grow much and the body proportions are like a child’s.
  • Oversecretion (hypersecretion) of GH in the childhood causes gigantism. In this condition, the child has very tall skeleton and proportionately large muscles The oversecretion of GH in an adult leads to overgrowth of the bones and jaw bone and bowing of the spine. This condition is called acromegaly.

 

Endocrine-system-Effect-of-hypersecretion-and-hyposecretion-of -GH

a. Gigantism

b. Dwarfism

Thyroid-stimulating hormone (TSH)

  • It controls the growth and functioning of the thyroid gland.
  • It stimulates the thyroid gland to produce thyroxine.

Adrenocorticotropic hormone (ACTH)

  • It regulates the activity of adrenal cortex.

Gonad stimulating (Gonadotropic) hormones

a. Follicle stimulating hormone (FSH)

  • In males, it stimulates the process of spermatogenesis.
  • In females, it stimulates the follicle cells in the ovaries to develop into mature eggs and also stimulates them to produce estrogen.

b. Luteinizing hormone (LH)

  • In males, it stimulates the secretion of testosterone, which in turn influences the appearance of secondary sexual characteristics.
  • In females, it stimulates the secretion of estrogen and progesterone, which in turn influence the process of ovulation, formation, and maintenance of corpus luteum and appearance of secondary sexual characteristics.

Tropic hormone

A hormone that stimulates other endocrine glands to produce/secrete their specific hormone.

Prolactin hormone (PRL)

  • In females, it enhances mammary gland development and milk production.
  • In males, it enhances the production of testosterone.

Hormones of the posterior pituitary

  • The posterior pituitary stores two hormones, antidiuretic hormone (ADH) also called vasopressin, and oxytocin. Both these hormones are produced and released by hypothalamus (and not by the pituitary as given in most books). These hormones are transported to posterior pituitary and stored there.

Antidiuretic hormone (ADH) or vasopressin

  • It promotes reabsorption of water from the kidney tubules. Thus, it causes the kidney to form more and more concentrated urine.
  • It constricts blood vessels with the rise in blood pressure.
  • The deficiency of ADH causes diabetes insipidus. In this disease, a person urinates more frequently and a large amount of urine is produced each time. This results in the loss of water from the body and the person feels thirsty. In diabetes insipidus, the urine does not contain any sugar.

Oxytocin

  • It stimulates vigorous contraction of the uterus during labor, leading to the childbirth.
  • It also causes the release of milk from the breast of a nursing mother.

Hormones of intermediate lobe of pituitary

It secretes melanocyte-stimulating hormone (MSH), that stimulates skin to secrete melanocytes (melanin pigment).

Summary of major hormones secreted in human body, their source glands and principal functions are given in Table

Endocrine system Major hormones secreter in the human their source and principal functions 14

Endocrine system Major hormones secreter in the human their source and principal functions 15

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Feedback Mechanism Of Hormone Secretion

As we know, hormones are required for various functions in our body. To perform these functions, a

Endocrine-system-Feedback-mechanism-by-pituitary-to-release-TSH-16

  • particular hormone may be required in a particular amount at a particular time, for which a control system is required. A control system should have a feedback mechanism to prevent excessive reaction or over-reaction. For example, the hypothalamus produces thyrotropin-releasing hormone (TRH), which in turn stimulates the anterior pituitary to produce thyroid-stimulating hormone (TSH). The TSH activates the thyroid gland to
  • secrete thyroxine. If the level of thyroxine in the blood is less than normal, it has a positive feedback effect on the hypothalamus and pituitary to produce more TRH and TSH, respectively. If the level of thyroxine is more than normal in the blood, a negative feedback effect is seen on the hypothalamus and the pituitary so that they produce less of TRH and TSH, respectively. Positive feedback systems are relatively rare in higher vertebrates as they lead to instability.
  • Thyroid-stimulating hormone (TSH) and thyroxine regulate each other’s level just like the requirement-supply kind of situation. Such a system of opposing effects leads to proper control and balance in a system. The two opposing systems work in coordination and help the body to adjust its output accordingly. The ultimate. effect of such a feedback system is to maintain homeostasis.

UP Board Notes For Class 10 Science Chapter 12 Endocrine System And Adolescence Summary

  • Hormones are chemical messengers secreted by endocrine glands and carried by blood or lymph to a target organ elsewhere in the body to stimulate a specific physiological change.
  • Hormones (1) are secreted in minute quantity, (2) are specific chemical messengers, (3) regulate physiological processes by chemical means, (4) are secreted by ductless (endocrine) glands, (5) are poured directly into the bloodstream, and (6) their action is very rapid and they act on a specific target, away from the source.
  • Adrenal glands are also called suprarenal glands. Each
  • adrenal gland has an outer region called cortex and an inner region called medulla.
  • Adrenal cortex secretes glucocorticoids and mineralocorticoids.
  • Glucocorticoids regulate metabolism of proteins, fats and carbohydrates in the body and regulate blood
  • pressure and heartbeat rate and are called emergency hormones.
  • Mineralocorticoids (aldosterone) control reabsorption of sodium in kidney tubules.
  • Adrenal medulla secretes adrenalin and noradrenalin hormones. Both these hormones together control emotions, fear, anger, blood
  • Thyroid gland is situated in the neck region. It secretes two hormones – thyroxine and calcitonin.
  • Thyroxine stimulates rate of cellular oxidation and basal metabolism.
  • Calcitonin regulates calcium and phosphate levels in the blood.
  • Pancreas produces Insulin from beta cells and glucagon from alpha cells of islets of Langerhans.
  • Insulin regulates conversion of glucose to glycogen.
  •  Hyposecretion of insulin causes diabetes mellitus.
  • Glucagon regulates the conversion of glycogen and some non-carbohydrates back to glucose.
  • Pituitary gland has three lobes – anterior lobe, posterior lobe, and intermediate lobe.
  • Anterior pituitary secretes six main hormones –
  • Growth hormone (GH) controls the overall growth of the body. Its hyposecretion causes dwarfism and hypersecretion causes gigantism in children.
  • Adrenocorticotropic hormone (ACTH) controls the growth and function of the adrenal cortex.
  • Thyroid-stimulating hormone (TSH) controls the growth and function of the thyroid gland. It stimulates thyroid gland to produce thyroxine.
  •  Follicle-stimulating hormone (FSH) stimulates process of spermatogenesis in males and ovulation in females.
  • Luteinizing hormone (LH) stimulates secretion of testosterone in males and estrogen and progesterone in females.
  • Prolactin (PRL) causes mammary gland development and milk production in females.
  • Posterior pituitary stores two hormones – antidiuretic hormone (ADH) and oxytocin.
  • ADH controls reabsorption of water in the kidney tubules. Its deficiency causes diabetes insipidus.
  • Oxytocin controls contraction of uterine muscles at the time of childbirth. It also helps in milk ejection from mammary glands.
  •  Hormone production is regulated by a feedback mechanism.

UP Board Notes for Class 10 Science Chapter 13 Reproductive System

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UP Board Notes For Class 10 Science Chapter 13 Reproductive System Learning Objectives

After completing this chapter, you will be able to:

  • Define reproduction and differentiate between asexual and sexual reproduction;
  • Illustrate male and female reproductive systems in humans and state the functions of each part;
  • Draw labelled diagrams of male and female reproductive systems;
  • Describe the histology of human testis and ovary;
  • Describe the main events in the process of reproduction In humans, starting from the production of gametes to pregnancy and childbirth;
  • Describe the process of exchange of nutrients and respiratory gases between an embryo and Its mother,
  • Explain how twins are produced.

Reproduction is a process by which a living organism is able to produce more of its own
kind. Reproduction involves the transmission of genetic material from the parents to the children, thereby ensuring that characteristics not only of the species but also of the parents, are perpetuated. Reproduction ensures continuity of life and survival of a species on the earth. In this chapter, you will learn about the organs for reproduction, fertilization, menstruation, and development of embryo in human beings.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Types Of Reproduction

There are two types of reproduction in living organismis – asexual and sexual reproduction.

Asexual reproduction involves the production of offspring from a single organism without the fusion of gametes. It is a common process of reproduction in lower group of plants and lower group of animals.

Sexual reproduction is a type of reproduction in which both sexes, the male and the female, are generally involved. It is the production of offspring by the fusion of the genetic material contained in the sex cells or gametes. As a result of fertilization, the male and the female gametes unite to form a zygote, which develops into an organism. Most animals and higher group of plants multiply by sexual reproduction.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Sexual Reproduction In Humans

Humans reproduce sexually. The reproduction in humans can be studied in two parts –

  • reproductive system in human beings, and
  • fertilization, pregnancy and development of the embryo.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System In Human Beings

The reproductive organs in human beings become functional after attaining sexual maturity. The period during adolescence in which the body attains sexual maturity is called puberty. Girls (females) attain puberty earlier than boys (males). In males, sexual maturity is attained at an age of 13-14 years. In females, onset of menstruation takes place around the age of 13 years. This age is known as the age of puberty. During sexual maturity, hormonal changes take place in males and females, and under the influence of these hormones, secondary sexual characteristics are developed.

Secondary sexual characteristics in males develop under the influence of testosterone, a hormone secreted by testes in males. These characteristics Include deepening of voice, widening of shoulders, appearance of beard and moustache, growth of axillary and pubic hair, enlargement of external genital organs and formation of sperms.

Secondary sexual characteristics in females include growth of axillary and pubic hair, widening of pelvis and hip, enlargement of breasts and onset of the menstrual cycle.

Primary reproductive parts and accessory reproductive parts

Primary reproductive parts include gonads (testes in males and ovaries in females). These are the sites of gamete production – sperms in testes and eggs in ovaries.

Accessory reproductive parts include all other structures that help in transfer of sex cells (gametes) and their fusion leading to fertilization and also growth and development of zygote till the birth of the baby.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Male Reproductive System

The male reproductive system consists of the following organs – a pair of testes, a pair of epididymis, a pair of sperm duct (vasa deferentia; singular: vas deferens), urethra, penis and accessory glands.

Reproductive-system-Position-of-male-reproductive-organs in-human-body-b.-Male-reproductive-organs-in-vertical-section-1

Reproductive-system-Functions-of-main-reproductive-organs-in-the-human-male-2

Testes

  • Testes (singular: testis) are the male gonads. A pair of testes are present in a human male.
  • These are present in a thin pouch made up of skin and connective tissue called scrotal sac or scrotum. Thus, testes are extra-abdominal. The scrotum is divided into right and left compartments by a muscular septum. One testis lies in each compartment.

Reproductive-system-Testis-and-associated-structures-3

  • In the embryonic stage, the testes are contained within abdomen. They descend down just before birth.
  • The high temperature of body does not allow maturation of sperms. Thus, the scrotum acts as thermoregulator, and it helps in maintaining the temperature at about 2-3°C lower than the body temperature. This temperature is suitable for the development of sperms.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System  Structure Of Testes

  • Each testis is encased in a capsule of white fibrous connective tissue called tunica albuginea. This tissue extends internally as septa, dividing the testis into 15-20 lobules.
  • Each testicular lobule has several highly coiled tubules called seminiferous tubules which are the sites of the maturation of spermatozoa. The process of maturation and differentiation of sperm inside the testes called spermatogenesis.
  • Between the seminiferous tubules, clumps of interstitial cells (packing tissue), also called Leydig cells are present. These cells secrete the male sex hormone, testosterone. This hormone regulates the maintenance of primary and secondary sexual characteristics in males.

Epididymis

From each testis arises a network of ducts called efferent ducts. These open into a common tube-like structure. This single, 6 m long, highly coiled tube where sperms are stored, get concentrated and become physiologically (mature) active, is called epididymis. It remains attached to the testis and lies within the scrotal sac.

Vas deferens (Sperm ducts)

  • Each epididymis continues from its lower end as a vas deferens. It enters the abdominal cavity through the inguinal canal, passes over the urinary bladder and joins the duct of seminal vesicle to form the ejaculatory duct. The ejaculatory duct opens into the urethra.
  • The inguinal canal allows the descent of the testes along with their ducts, nerves and blood vessels from the abdomen to the scrotal sacs just before birth. Sometimes, because of high pressure in the abdomen, the intestine bulges into the scrotum through this inguinal canal and causes inguinal hernia.

Urethra

  • The male urethra is about 15-20 cm in length and is differentiated into three parts – an anterior prostatic
  • part which passes through the prostate gland, a middle membranous part, and a posterior penile part which passes through the copulatory organ, the penis.
  • The male urethra functions as a passage for both semen and urine. The sperm ducts from each testis open into the urethra near its anterior end.

Penis

  • Penis is the copulatory organ in males. It is a cylindrical, spongy and a highly vascular organ. It consists of erectile tissue permeated by blood sinuses. The urethra runs through it centrally and serves as a common passage for the exit of urine and semen. It is used to deposit spermatozoa in the female genital tract.
  • During sexual excitement, the spongy tissue gets filled up with blood, as the arteries in it dilate. This condition is known as erection. Externally, the penis is covered by skin. The tip of the penis is soft and highly sensitive. It is called glans penis. It is covered by a loose retractile fold of skin called prepuce.

Accessory glands

There are three accessory glands in males. These include seminal vesicles, prostate gland and Cowper’s glands.

1. Seminal vesicles: A pair of seminal vesicles are present at the base of the urinary bladder. The function of the seminal vesicles is to secrete seminal fluid that acts as a medium of transport for the spermatozoa through the sperm duct. The seminal fluid is an alkaline viscous fluid which contains fructose, which provides energy to the sperms. This secretion forms about 60 per cent of the ejaculate. Sperms get active when mixed with seminal fluid.

2. Prostate gland: It is a single gland that surrounds the upper part of the urethra. The alkaline nature. of this fluid neutralizes the acid in the female tract which would otherwise inactivate and kill the sperms.

3. Cowper’s glands or lbourethra glands: These paired glands lie below the prostate gland and join the urethra at a short distance from that of the prostate gland. They secrete a white, viscous, alkaline secretion resembling mucus, which acts as a lubricant.

Spermatozoa and semen

The spermatozoa are minute gametes produced by the testes in males. They are immotile when stored in the epididymis but get activated and motile by the secretions from the accessory reproductive glands in males. The secretions of various accessory glands along with sperms form the semen.

The sperms are released in millions. In one ejaculation about 200,000,000 (2 x 10³) sperms are discharged. Sperms move with the speed of
2 mm/minute in the female tract.

Structurally, a human sperm has three main parts – head, neck and tail. The tip of a sperm is covered by a cap-like structure, acrosome, which helps the sperm to penetrate inside the egg during fertilization.

Acrosome also releases an enzyme (hyaluronidase) which enables the entry of the sperm into the egg by dissolving the proteinaceous wall around the egg. The general structure of a sperm is shown in.

Reproductive-system-Structure-of-a-sperm-4

The nucleus of the sperm contains genetic material that is transferred to egg and mixes with the female nucleus during fertilization. The middle piece of the sperm contains mitochondria that provide energy for sperm penetration and sperm motility.

The tail helps the sperm in moving forward through the liquid medium while swimming.

The course of sperm movement from their production in the testes to reach the urethra in penis is given in.

Reproductive-system-the-course-of-sperm-movement-in-male

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Female Reproductive system

The female reproductive system consists of the following organs – a pair of ovaries, a pair of Fallopian tubes, uterus, vagina and external genitalia. Important functions of the main reproductive organs in the human female are listed in.

Ovaries

A pair of almond-shaped or ovoid-shaped ovaries lie in the lower part of the abdominal cavity, one on each side of the uterus. Each ovary is attached to the

Reproductive-system-Female-reproductive-organs-in-human-beings-6

Reproductive-system-Functions-of-main-reproductive-organs-in-the-human-female-7

Reproductive-system-enlarged-view-of-fallopian-tube-and-ovary

Oogenesis

Eggs can be observed in various stages of development inside the ovary. The egg mother cells or oogonia are diploid cells that undergo meiosis to produce the haploid egg or ovum.

  • During the process of development the egg gets surrounded by some special cells called
    follicular cells or nurse cells. Nurse cells provide nourishment to the developing egg cell.
  • The egg cell along with its surrounding nurse cells is called a follicle.
  • Towards the end of oogenesis, the follicle develops a fluid-filled cavity amongst the nurse cells and is called the tertiary follicle or Graafian follicle.
  • Upon maturation, the follicle ruptures, the ovarian wall ruptures and the ovum is released out of the ovary. This egg is sucked by the funnel of the oviduct or Fallopian tube. The egg is in the secondary oocyte stage as the meiosis is not yet complete. It has a proteinaceous layer around it called the zona pellucida.

Fallopian tubes (Oviducts)

There are two oviducts or Fallopian tubes or uterine tubes in the human female reproductive system. Each oviduct is about 10-15 cm long. The proximal funnel-shaped end of each oviduct lies near the ovary and is called infundibulum.

Its margin bears finger-like projections called fimbrae. Each infundibulum continues as a thin and coiled tube called oviduct or Fallopian tube. Both Fallopian tubes open into the uterus.

The egg released from the ovary is sent into the Fallopian tube by the infundibulum. The Fallopian tube transports the ovum from the ovaries into the uterus by cilia along the wall of funnel and peristaltic contractions of the muscles of the tube wall. Fertilization of ovum and sperm is taking place in Fallopian tube.

Uterus

The uterus is a hollow, pear-shaped, muscular, thick- walled organ located in the pelvic cavity between urinary bladder and rectum. Its upper broader portion is called corpus uteri (body of the womb) and the lower narrow portion is called cervix uteri (neck of the womb).

The innermost wall of the uterus is called endometrium. It is richly supplied with blood vessels as implantation of the embryo takes place in the endometrium. Cervix is mainly a sphincter muscle that closes the lower end of the uterus where it joins the vagina.

Vagina

It is a muscular tube, about 7-10 cm in length. Vagina is the organ where the spermatozoa are deposited during coitus (act of copulation) by the penis. It serves as the birth canal during childbirth (parturition) and also acts as a duct for the passage of uterine secretions and menstrual flow.

The opening of the vagina in young girls is partially closed by a thin membrane called hymen.

External genitalia (Vulva)

The external genitalia in human female (also called vulva) mainly consists of labia majora, labia minora and clitoris.

The labia majora (large lips) is a pair of thick folds of skin containing hair, sweat glands and sebaceous. glands. These folds lie one on either side of the vagina. The labia majora is equivalent to scrotum in males.

The labia minora (small lips) are two small folds of mucous membrane situated on the inner side of labia majora. They are devoid of hair and glands. The two folds of labia majora and labia minora, comprise the vulva. The clitoris is a small erectile organ which

is highly sensitive and is located at the junction of the labia minora. The clitoris corresponds to the penis in males.

The vagina opens to the outside by an opening into the depression between the vulva called vestibulum. In a human female, the urethra and the genital duct have separate openings.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Menstrual cycle in human females

In a human female, the fertility period extends from the age of puberty, i.e. about 12-13 years up to menopause, i.e. 45-50 years. The stage of puberty is marked by the appearance of secondary sexual

Reproductive-system-Transverse-section-through-an-ovary-9

Transverse section through an ovary

Reproductive-system Scanning-electro- micrograph of egg-surrounded-by-follicle-cells-10

Scanning electron micrograph of egg surrounded by follicle cells

characteristics. Thus, puberty is a period in which reproductive system matures and becomes capable for reproducing. At the time of menopause, ovulation and menstruation stop and the reproductive organs decrease in size.

During each menstrual cycle, an ovum is matured and released once every 28 days. The period of menstrual cycle is counted from the day of onset of menstrual flow to the next onset after about 28 days. There are four phases of menstrual cycle as given below.

Menstrual phase

The menstrual cycle starts with the menstrual flow, during which the cellular lining of the uterus, with blood flow, is shed off. This process continues for 3-5 days. During menstrual phase, the ovary starts to process a new egg in follicle.

Follicular phase

From the 5th day up to the 13th day of the onset of menstrual cycle, growth and maturation of the Graafian follicle take place. Graafian follicle is the final stage in the maturation of an ovum inside the ovary.

It consists of an ovum and a mass of nurse cells or follicular cells surrounding it. The Graafian follicle produces a hormone, oestrogen. This hormone stimulates the uterus to prepare itself to receive the ovum. The cells lining the uterus grow rapidly and develop a dense network of blood vessels.

Reproductive system Changes in the female reproductiv-system-that-occur-during-the-menstrual-cycle-11

Ovulatory Phase

In this phase, ovulation takes place. The Graafian follicle ruptures to release the ovum. The cells of the ruptured follicle form the corpus luteum that secretes the hormone, progesterone.

The release of the ovum from the ovary is called ovulation. The ovum reaches the uterus via the Fallopian tube on the 13th or 14th day and remains = there up to the 16th day (for 48-72 hours).

Luteal Phase

If the ovum does not get fertilized by any sperm during the ovulatory period then it degenerates. At the end of the 28th day, this ovum is rejected along with the uterine lining.

This marks the onset of the disintegration of the thickened endometrial lining of the uterus – the next menstrual cycle. The remnant corpus luteum develops of the Graafian follicle in the ovary turns into corpus luteum.

If the ovum gets fertilized while in the Fallopian tube, it starts dividing by repeated mitotic divisions called cleavage divisions. The egg is now an early embryo. It reaches the uterus within 5-7 days of fertilization and implants itself in the thick endometrium.

The female is now pregnant and shall give birth to a baby after the development of embryo in 38-40 weeks. This is the gestation period.

What happens to the menstrual cycle if the ovum receives sperm?

If the ovum receives sperm, menstruation (and ovulation) cease for as long as the woman is pregnant. This is because level of progesterone increases by the corpus luteum (which persists in the ovary) and later by the placenta. Progesterone prevents egg maturation in the ovary.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Fertilization, Pregnancy And Development Of The Embryo

  •  Fertilization: The sexual intercourse, also known as coitus, is the first step towards pregnancy.

Reproductive-system-Highly-magnified-view-of-a-human-ovum-and-stages showing-ts-fertilization-12

  • During intercourse, the semen containing sperms is ejaculated in the vagina. This is known as copulation. A single ejaculation may contains 2-4 hundred million sperms, only one will actually fertilize the egg.
  • The spermatozoa are deposited high up in the vagina close to the cervix. They reach the top of the Fallopian tube within 5 minutes of their release due to their motility and contractions in the walls of uterus and Fallopian tube. Spermatozoa remain viable in the female genital tract for 24-72 hours.
  • If the ovum receives a sperm during the ovulatory period, the two fuse to form a zygote. This act of fusion of the male gamete (sperm) and the fernale gamete (ovum) to form zygote is called fertilization. About 13-15 days of the menstrual cycle are most favourable for conception. Of the millions of sperms ejaculated in the vagina, the first one to reach the ovum fertilizes it. Only one sperm can fertilize the ovum. This is possible due to a protein coat formed around the ovum soon after the first sperm comes in contact with the ovum.

Reproductive-system-developmentof-an-egg-ovulation-fertillization and-its-implantation

  • Implantation: The zygote immediately begins to divide by rapid mitotic divisions called cleavage. The daughter cells produced by cleavage divisions get smaller and smaller progressively. Successive cleavages produce a solid mass of cells called the morula which appears like mulberry on the outside. It’s volume is the same as that of the zygote. With further development, this ball of cells becomes hollow and is called blastocyst. The cells of blastocyst are now differentiated into two types.
  • Trophoblast: outer compact layer cells
  • Inner Cell Mass (ICM): inner mass of cells located at one end of the hollow ball. Also called embryoblast cells.

The blastocyst is still enclosed in Zona Pellucida which was present around the ovum at ovulation. The blastocyst passes down to the uterus and fixes itself to the endometrium wall of the uterus. The fixing of blastocyst in the endometrium of the uterus is called

implantation and the female is said to be pregnant or in the stage of pregnancy. Implantation takes place about a week after fertilization.

How does the blastocyst implant in the uterine wall?

Site of implantation: Endometrium of the uterine wall Time of implantation: 5-7 days of fertilization

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Process Of Implantation

  • Trophoblast cells secrete enzymes that perforate the Zona pellucida and the blastocyst oozes out.
  • The special trophoblast cells secrete enzymes that digest and liquefy the endometrial cells at a point creating a pit.
  • Blastocyst starts burrowing itself into the pit.
  • Eventually, the blastocyst gets completely buried in the endometrium.
  • Blastocyst is oriented in such a direction that the ICM faces towards the wall.
  • Trophoblast develops further to form a connection between the embryo and the mother called the placenta.

Placenta

The developing embryo is attached to the uterine wall by the placenta. Placenta is an association between maternal and foetal tissue meant for physiological exchange. Umbilical cord is a tough structure that serves as the blood-vascular connection between the foetus and placenta. It develops from embryonic cells.

Reproductive-system -Placenta-14

The placenta is formed of fine finger-like processes called villi. There are two sets of villi. One set of villi is given out by the uterine wall which opens up in a pool or sinusoid of blood of mother while the other set is an extension from the embryo.

These two sets of villi are interlocked but they do not open into each other. Thus, although the blood of the mother and the embryo are in close contact with each other, the two do not get mixed.

Oxygen and nutrients diffuse from the mother’s blood into the capillaries of the villi. From here they

Reproductive-system -Development-of-embryo-within-the-uteru-15

are carried by the blood vessels in the umbilical cord to the foetus. Conversely, carbon dioxide and other wastes are carried back by foetal blood and transferred to the mother’s blood through the villi in placenta.

The villi from the embryonic side arise from the trophoblast cells and get lined by chorion and not allantois in humans, which is the outermost lining of the developing embryo.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Functions Of Placenta

  • Nutrition: Placenta serves as a tissue through which oxygen and nutrients (glucose, amino acids and salts) are supplied from the maternal blood to the foetus.
  • Excretion: It also transports carbon dioxide and excretory waste from the foetal blood to the maternal blood.
  • All these substances move across the placenta by diffusion. Placenta is permeable to respiratory gases, nutrients and antibodies. It prevents harmful material from reaching the embryo. It does not allow the passage of germs from the mother to the embryo. However, certain exceptions like German measles virus and HIV can pass through the mother’s blood to the embryo.
  • Endocrine: Placenta also produces two hormones – progesterone and oestrogen. Under the influence of these hormones, neither ovulation nor menstruation takes place till pregnancy continues. However, these phenomena are resumed after childbirth.

Reproductive-system-Sequence-of-events-in-development-of-the-embryo-16

Foetal membranes

During development, the embryo gets surrounded by four special membranes which protect and nourish it. These are as follows:

  •  Yolk sac: contains nutrients
  • Allantois: acts as a waste bag

The first two are non-functional in humans as this work is done by placenta.

  • Chorion: outermost membrane, takes part in placenta formation from the embryonic side.
  • Amnion: a membranous sac filled with amniotic fluid, completely envelops the developing foetus.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Functions Of Amnion

  • Acts as a shock absorber for the developing foetus and protects from any physical damage.
  • Assists in regulation of foetal body temperature.
  • Prevents adhesion (sticking) of skin of foetus to the surrounding tissues.
  • Allows movements of the foetus in the mother’s womb, in a restricted manner.

Amniocentesis Embryonic cells are sloughed off in the amniotic fluid. These cells found in the amniotic fluid are studied by a technique called amniocentesis. In this method, some amount of amniotic fluld is taken by a surgical needle inserted into the amniotic sac through the abdomen.

The embryonic cells are studied for any genetic abnormalities in the child months before birth, by 16-18 weeks of development.

Gestation and parturition

Parturition is the process of childbirth. The sequence of events that occur during childbirth is called labour.

What happens during childbirth?

During Childbirth  

  • The uterus undergoes rhythmic contractions. The amnion bursts and the amniotic fluid is discharged.
  • The uterus contracts powerfully, expelling the baby.
  • The baby’s lungs start functioning and the baby takes its first breath.
  • The umbilical cord is tied and cut.
  • The lung bypasses close so that blood flows to the lungs.
  • The placenta is discharged (after birth).
  • The breasts start producing milk.

The period of complete development of the foetus from the beginning of the last menstrual period till birth of the baby is called gestation period. It is of about 280 days.

Reproductive-system-Birth-of-a-chil-17

Test tube babies Some women are unable to have babies due to certain reasons. This problem can be overcome by the test tube baby technique.

Reproductive-system-Production-of-test-tube-babies-18

In this technique, one or more ripe ova are sucked from a woman’s ovaries using a special syringe. These ova are placed in a dish containing sperms from her partner. During this time, sperm fertilizes the ovum to form zygote which divides to form an embryo. The embryo is then inserted into the woman’s uterus where there is a chance it will implant and develop into a baby.

The entire process is performed under optimum conditions in a laboratory. The general notion is that people in a laboratory work with test tubes, hence the name test tube baby.

UP Board Notes For Class 10 Science Chapter 13 Reproductive System How Twins Occur?

Occurrence Of Twins

Usually, only one ovum is released by an ovary in every reproductive cycle. If this ovum gets fertilized, one baby is born. But sometimes more than one egg may be released and fertilized. Or an ovum may divide into two or more separate cells after fertilization. This is how twins, triplets, quadruplets, etc. are produced.

Identical twins

Identical twins are the result of a fertilized egg/zygote separating into two cells after the first cleavage division. Both of which continue to divide, so two identical embryos come from the same egg and sperm. Such twins look alike and are of same sex. Since identical twins develop from the same zygote, these are called monozygotic twins.

Non-identical or fraternal twins

Non-identical twins occur when two eggs are produced at the same time and each is fertilized by a different spermatozoa. These twins do not resemble each other physically. They can be of the same sex or different sexes. Since fraternal twins develop from two different zygotes, they are called dizygotic twins.

Reproductive-system-Types-of-twins-19  

UP Board Notes For Class 10 Science Chapter 13 Reproductive System Summary

  • Reproduction is a process by which a living organism is able to produce more of its own kind.
  • In sexual reproduction, both male and female gametes are produced and the process of fertilization takes place. The humans reproduce sexually.
  • The age of 13-14 years in males and 12-13 years in females is called puberty. At this age, sex organs get matured and several secondary sexual characteristics appear in them.
  • The male reproductive system consists of – a pair of testes, a pair of epididymis, a pair of vasa deferentia, urethra, penis and accessory glands.
  • The female reproductive system consists of a pair of ovaries, a pair of Fallopian tubes, uterus, vagina and external genitalia.
  • The fusion of male gamete (sperm) and female gamete (egg) to form a zygote is called fertilization.
  • The fixing of a fertilized egg in the form of mass of cells (blastocyst) in the uterine wall is called implantation.
  • Placenta Is an association between maternal and foetal tissues meant for physiological exchange.
  • Amnion contains amniotic fluid which surrounds the foetus in placenta and acts as a shock absorber.
  • Twins are of two types – fraternal and identical twins.

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UP Board Notes for Class 10 Science Chapter 8 The Circulatory System

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UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Learning Objectives

After completing this chapter, you will be able to:

  • Describe the composition, physical characteristics and functions of blood; describe the ABO blood groups and the Rh factor;
  • Describe the structure and functions of the heart;
  • Trace the pathway of blood circulation through the heart;
  • Name the major blood vessels entering and leaving the heart;
  • Describe the cardiac cycle and heart sounds;
  • Differentiate between arteries, veins and capillaries;
  • Differentiate between systemic and pulmonary circulations;
  • Describe the structure and distribution of lymphatic vessels and their functions;
  • Differentiate between blood and lymph.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Circulation Of Fluids In Humans

  • In human beings, a rapid supply of nutrients, oxygen and hormones to various tissues and the immediate disposal of waste products are essential requirements. So, our body has a specialized circulatory system. The circulatory system has three main parts.
  1. Circulatory medium – Blood, tissue fluid and lymph
  2.  Blood vessels – Arteries, veins and capillaries
  3.  Pumping organ – Heart The circulatory system, in different animals, are of two types – open and closed. The differences between the two are given in Table.

The-circulatory-system-Differences-between-closed-circulatory-system-and-open-circulatory-system

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Circulatory Medium – Blood, Tissue Fluid and Lymph

Our body has three different types of fluids:

  1. Blood- Found in the heart and blood vessels (arteries, veins and capillaries)
  2. Tissue fluid – Found in the intercellular spaces
  3. Lymph-Found in the lymph vessels and lymphatic organs (e.g. spleen and tonsils)

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Blood – Composition And Functions

  • An average human being has about 5.5 litres of blood in his body. About 50-60 per cent of the blood is a fluid called plasma and the remaining 40-50 per cent is made of cellular elements called corpuscles that are held in suspension. Blood always flows from the heart through the arteries and back to the heart through the veins.

Physical properties of the blood

  • Blood is a red-coloured, viscous and complex tissue fluid. It is salty in taste and slightly alkaline with a pH range of 7.35-7.45. Blood constitutes about 6 to 8 per cent of the total body weight.

Composition of blood

  • Blood is made up of two main components – plasma (fluid part) and cellular or formed elements (blood corpuscles, solid part).

The circulatory system Composition of blood

Plasma – the fluid part

  • Plasma is a straw-coloured aqueous part of the blood in which formed elements remain suspended. It forms about 50-60 per cent of the blood volume. Plasma contains water (about 90-92 per cent), inorganic salts (about 1-2 per cent) and organic compounds (about 7-8 per cent).
  1. Plasma = Blood – Formed elements
  2. Plasma from which the protein fibrinogen has been removed is called serum.
  3. Serum Plasma – Fibrinogen

Cellular elements

  • In human beings, three types of cellular elements are found suspended in the plasma.
  • Red blood corpuscles (RBCs) or erythrocytes
  • White blood corpuscles (WBCs) or leucocytes
  • Platelets or thrombocytes

The process by which new blood cells are formed is called haemopoiesis or haematopoiesis.

The circulatory system Three types of cellular elements suspended in the plasma

The circulatory system Centers of blood cell production

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Red Blood Corpuscles (RBCs)

  • Red blood corpuscles or erythrocytes (Gk. erythrose: red) are biconcave and enucleated (i.e. without a nucleus), disc-like cells which are flat in the centre, and thick and rounded at the periphery. Young RBCs have a nucleus, but as they mature, the nucleus degenerates. Such a shape is of great advantage to RBCs as it increases their surface area.
  • Due to the lack of organelles (such as mitochondria and endoplasmic reticulum), their oxygen demand is negligible.
  • The RBCs are very small in size. This small size helps them in absorbing oxygen and enables them to move in very fine blood capillaries throughout the body of a person.
  • RBCs are produced in the bone marrow of long bones, ribs, vertebrae and skull bones. The average life span of erythrocytes is about 120 days.
  • Their average number ranges from 5 million to 5.5 million in human males and 4.5 million to 5 million in human females.The circulatory system Erythrocytes

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Haemoglobin (Hb)

  • The RBCs have a colourless spongy body which contains haemoglobin. The haemoglobin is the respiratory pigment which is composed of an iron-containing part known as haeme and a protein part known as globin.
    The oxygen after diffusing into blood capillaries combines with the iron-containing part of RBCs and forms oxyhaemoglobin.
  • Absence of a nucleus and other organelles makes RBCs more efficient

1.  RBCs in mammals are enucleated when mature, that is, they lack a cell nucleus. This is attributed to their oxygen-carrying capacity. These cells become more efficient in their work because of the following reasons:

  •  More space is available for haemoglobin which carries oxygen.
  • The shape changes to a biconcave disc rather than a normal sphere, increasing the surface area volume ratio for a better exchange of oxygen and carbon dioxide.
  • The biconcave shape optimises the flow of the blood within blood vessels as these cells move in a laminar flow, i.e. in parallel rows without any swirls.
  • No nucleus means no DNA, so proteins cannot be synthesized. Their inability to carry out protein synthesis means they cannot be attacked by many viruses.

2. RBCs in mammals do not have mitochondria which is the site of cellular respiration. This ensures that all of the oxygen taken up by these cells from the lungs is delivered to the target tissue and not utilised by the cell itself.

3. RBCs also lack organelles like the Golgi apparatus and endoplasmic reticulum. This decreases their size markedly from 24 u to 7-9 μ and makes them small enough to pass through the smallest capillaries.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System White Blood Corpuscles (WBCs)

The circulatory system Differences between closed circulatory system-and-open-circulatory-system

White blood corpuscles

  • White blood corpuscles or leucocytes (Gk. Leucos: white) are rounded or Fig. irregular-shaped cells. They are capable of amoeboid movement. They are colourless since they lack haemoglobin.
  • They are produced in the bone marrow. Leucocytes are of two types –
  • granulocytes (contain granules in their cytoplasm and have lobed nuclei) and
  • agranulocytes (lack granules in their cytoplasm and have unlobed nuclei).

1. Granulocytes

Granulocytes are spherical in shape and larger than the red blood cells. They have lobed nuclei and their cytoplasm contains granules. There are three types of granulocytes – (a) neutrophils, (b) basophils and (c) eosinophils.

  • Neutrophils: Neutrophils account for 50-70% of the WBCs in our blood. Their cytoplasm contains very fine granules. The nucleus has 3-6 lobes. The granules stain with both acidic and basic. Dyes. Neutrophils are highly phagocytic in nature. Neutrophils contain special proteins called defensins, which have an antimicrobial activity against germs.
  • Basophils: Basophils account for only 0.5% of the total WBCs. They are of the same size or slightly smaller than neutrophils. The nucleus is indistinctly lobed. The cytoplasmic granules stain with basic dyes. Basophils produce histamine and heparin, which intensify the inflammatory response in an allergic reaction. During inflammation, the blood vessels dilate making their walls leaky for leucocytes to squeeze out of the blood capillaries and engulf the germs. This process is known as diapedesis.

The-circulatory-system-Inflammatory-response

 

  • Eosinophils: Eosinophils account for 1-4% of the total WBCs. The nucleus is two-lobed. The cytoplasmic granules are large and rough and stain dark red with acidic dyes (e.g. eosin). They phagocytose the antigen-antibody complex. They release chemicals to combat inflammation during an allergy.

2. Agranulocytes

Agranulocytes’ nucleus is single and typically spherical or kidney-shaped. The cytoplasm does not contain granules. There are two types of agranulocytes – (a) lymphocytes and (b) monocytes.

  • Lymphocytes: Lymphocytes account for about 25% of the total WBCs. The nucleus is large, and spherical, with a dent-like depression on one side, which occupies most of the cell volume. They produce antibodies and play a crucial role in immunity.
  • Monocytes: Monocytes are the largest leucocytes and account for 3-8% of the total WBCs. The nucleus is large and U- or kidney-shaped. They arephagocytic in nature and ingest germs and clean up damaged cells. Hence, monocytes are referred to as wandering macrophages.

The-circulatory-system-Type-of-white-blood-cells

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Functions Of WBCs

  • WBCs help in destroying solid substances and germs, especially bacteria, by engulfing them. This defensive process of fighting against disease-causing germs is termed as phagocytosis. Neutrophils are most active in this role. By doing so they protect the body from diseases, i.e. they are responsible for

immunity.

  • They also help in the formation of antibodies which neutralize or kill the germs that enter our body.

Inflammation

  • It is a defensive response of the body to tissue damage by microbes, physical agents or chemical agents. It is characterised by four fundamental symptoms – redness, pain, heat and swelling.
  • The following reasons of inflammation are given below:
  • Vasodilation, i.e. increase in diameter of surrounding blood vessels.
  • Increased permeability of blood vessels. It allows defensive substances in blood to enter the injured area and phagocytosis occurs.
    Thus, it is to be clearly understood here that inflammation is not a role of WBCs but phagocytosis at the point of inflammation is carried out by neutrophils and monocytes. In case of an allergic reaction, basophils intensify the inflammatory response.

Pyogenesis

  • (pyo = pus; genesis = to produce)
  • The phenomenon of pus production during an inflammation is pyogenesis. Pus is a thick whitish fluid which contains living and dead WBCs and dead tissue debris.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Blood Platelets (Thrombocytes)

  • Blood platelets are colourless, oval or round (plate-like in active form), cytoplasmic fragments formed from giant cells of the bone marrow. These are found floating in the blood. These are enucleated (without a nucleus), bound by a membrane and contain a few organelles. Their life span is about 5-10 days. Thrombocytes help in blood clotting. They release a chemical, thromboplastin that initiates the process of clotting of blood. They can repair slightly damaged blood vessels.

The-circulatory-system-Platelets

Let us understand…

  • An antigen is a protein produced by the body in response to the presence of an antigen and combines specifically to that antigen. WBCS act as antibodies by phagocytosing the antigen.
  • Toxin is a poisonous substance produced by an antigen (foreign body) which has unfavourable effects on the body of the organism. In other words, a toxin is toxic the Infected organism.
  • Toxoid is an activated or weakened toxin produced by an antigen which is not toxic anymore. However, it is still capable of acting as an antigen and hence, is used as a vaccine which stimulates production of specific antibodies in the blood of an organism.
  • Antibody neutralizes a specific antigen.

Blood diseases

  • An increase in the number of RBCs much more than normal is called polycythemia.
  • A decrease in the RBC count is called erythrocytopenia.
  • An enormous increase in WBCs at the cost of RBCs causes leukaemia – the blood cancer.
  • A decrease in the WBC count is known as leucopenia.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Functions Of Blood

Blood is a complex fluid which performs a number of roles in our body. It transports, regulates and protects.

1. Transportation

  • Transport of nutrients: The digested food substances are absorbed by the blood at the site of absorption (small intestine) and transported to different organs of the body.
  • Transport of respiratory gases: Blood transports oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the respiratory surface, i.e. lungs.
  • Transport of waste products: The metabolic waste substances produced in the body are transported by the blood to the excretory organs.
  • Transport of body secretions: Blood transports chemical secretions like hormones, from the site of their secretion (endocrine glands) to the target organs.

2. Regulation

  • Regulation of body temperature: Blood helps to control the body temperature by evenly distributing the heat produced in one part of the body to different parts.
  • Maintenance of pH: The plasma proteins are amphoteric in nature, i.e. they act as a buffer and thus maintain the pH of blood.
  • Water balance: Blood maintains water balance to a constant level by bringing about constant exchange of water between the circulating blood and the tissue fluid.

3. Protection

  • Clotting of blood protects against blood loss: Prothrombin and fibrinogen proteins of plasma help in blood clotting at the site of injury. This prevents blood loss.
  • Defence against infection: Blood contains WBCs that are phagocytic in nature. WBCs also produce antibodies that destroy the bacteria, after neutralizing their toxins, and thus, play a protective role.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Clotting Of Blood

  • Blood is in a fluid state when inside the blood vessels. Blood does not clot in uninjured vessels due to the presence of natural anticoagulants called heparin and antithrombin, produced in the liver. Blood usually clots after it escapes from the blood vessels.
  • When blood vessels get damaged due to any external injury or an internal cause, three basic mechanisms become operational in the following sequence:

Step 1. Vascular spasm occurs. When a blood vessel (artery or vein) other than a capillary is injured, the smooth muscles in its wall contract to reduce blood loss.

Step 2. Platelet plug formation occurs. The platelets get activated on coming in contact with the damaged blood vessel. Platelets undergo drastic changes in their shape and release several substances involved in the step of blood coagulation. The activated platelets become sticky and form a platelet plug at the damaged spot. This plug is initially loose and is tightened by the fibrin threads formed in the next step.

Step 3. Coagulation of blood occurs. The process of clotting of blood is known as coagulation. A clot is a network of insoluble protein fibres called fibrin in which the cellular components of the blood get trapped. Coagulation is a complex process in which several coagulation factors (I to XIII) come into action in a definite sequence. It can be divided into three basic stages as follows:

Stage 1. Formation of prothrombin activator: A protein called Tissue Factor (TF) or thromboplastin found on the surface of various body cells such as brain, lungs and intestines initiates the formation of prothrombin activator. It is a cascade of events which ends with the activation of the enzyme thrombokinase also called factor X or Stuart factor which in the presence of Ca++ ions forms a prothrombin activator. The Stuart factor is not released by platelet disintegration. However, bursting of platelets provides phospholipids that activate this factor.

Stage 2. Conversion of prothrombin to thrombin: The prothrombin activator formed in stage 1 now converts prothrombin to thrombin with the help of Ca++ ions.

Stage 3. Conversion of fibrinogen to fibrin: Fibrinogen is a soluble protein found in the plasma. Thrombin formed in stage 2 now converts soluble fibrinogen to insoluble fibrin in the presence of Catt ions.
The platelet plug is strengthened by fibrin which forms a network at the site of the injury. Thrombin also causes more platelets to adhere to each other thus strengthening the clot.

Clot Vs Thrombus

  • Intravascular clot formed in an unbroken blood vessel is called a thrombus. Every clot is not a thrombus.

The-circulatory-system-Mechanism-of-clotting-of-blood

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Blood Groups And Blood Transfusion

Blood groups

  • In 1901, Karl Landsteiner, a German biochemist, proposed that the blood of different individuals has some biochemical differences. There are two types of proteins in the human blood.
  1. Agglutinogen or antigen is present on the surface of RBCs. It is called the corpuscle factor.
  2. Agglutinin or antibody is a protein present in the blood plasma and is called the plasma factor. There are two kinds of antigens, A and B, and two kinds of antibodies, a and b, in the blood. Antigen A and antibody a are antagonistic or incompatible and cause self-clumping. Similarly, antigen B and antibody b are incompatible and cause self-clumping. Antigen A is compatible with antibody b and antigen B is compatible with antibody a.
  • On the basis of the type of antigen present on the surface of RBCs as given below, a system of blood groups known as ABO system, in which there are four blood groups, is recognized in the human blood.
  • Group A with antigen A and antibody b.
  • Group B with antigen B and antibody a.
  • Group AB with both A and B antigens but no antibodies.

The-circulatory-system-Human-blood-groups-and-their-compatibility

  • Group O has no antigen but both antibodies a and b.

Blood transfusion

  • Blood transfusion is a procedure of transfer of blood or blood components from one person (donor) into the bloodstream of another person (recipient). The antigens of the donor’s blood can react with antibodies of the recipient’s blood and cause clumping of RBCs. Thus, antigen A present in the RBCs of blood group A individuals reacts with antibodies of plasma of blood group B individuals and vice versa. This phenomenon is known as agglutination. Agglutination may cause serious consequences and even prove fatal.
  • The RBCs of blood group O individuals lack antigens and are not clumped by antibodies present in the serum of the recipient’s blood. It means blood group O can be given to persons with blood group O, A, B or AB. Hence, persons with blood group O are called universal donors.
  • However, persons with blood group AB lack antibodies in their plasma, so they can receive blood from A, B, O or AB blood groups. Such persons are called universal recipients.

Rh factor (Rhesus antigens)

  • Landsteiner and Wiener discovered in 1940 that the surface of human RBCs contains a protein that is also found in the RBCs of Rhesus monkeys. So, it was termed an Rh antigen or Rh factor. Those persons who have this factor are called Rh-positive and others as Rh-negative.
  • Both Rh-positive and Rh-negative persons are quite normal. The problem arises when Rh- blood comes in contact with Rh+ blood either due to blood transfusion or during pregnancy.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Incompatibility During Blood Transfusion

  • The Rh-blood can be given safely to an Rh+ individual. When Rh* blood is transfused into an Rh- person, the recipient forms antibodies in her/his blood. However, no complications develop after the first transfusion.
  • In case of a second transfusion of Rh* blood to an Rh person, the recipient’s anti-Rh factors attack and destroy the donor’s red blood corpuscles. Therefore, it is always advised that the patient’s Rh factor is determined before transfusion.

Incompatibility during pregnancy

  • A serious problem arises if an Rh™ mother is carrying an Rh foetus. The Rh blood of the foetus will stimulate the formation of anti-Rh factors or antibodies in the mother’s blood. During the first pregnancy, enough antibodies are not produced to harm the foetus.
  • During the second pregnancy, if the foetus is Rh*, more antibodies will be produced in mother’s blood. Due to the cumulative effect of antibodies produced the second time, in addition to the antibodies already present in mother’s blood, a large number of RBCs of the foetus are destroyed. This causes death of the foetus. This called erythroblastosis fetalis.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Parts Of Human Circulatory System

Blood vessels 1

  • The blood vessels are a system of channels through which the blood flows. There are three kinds of blood vessels – arteries, veins and capillaries.

1. Arteries are the blood vessels that carry blood away from the heart to the various parts of the body.

  • All arteries (except the pulmonary artery) carry oxygenated blood.
  • An artery has thick and elastic muscular walls.
  • Arteries have a small lumen without valves.
  • The blood flows in spurts in arteries corresponding with contractions of the ventricles in the heart.

2. Capillaries are microscopic, thin vessels that carry blood from arterioles to small their venules.

  • They are found abundant in those tissues or organs where the rate of metabolism is very fast.
  • Capillaries are made of single-layered endothelial tissue with a very narrow lumen.

The-circulatory-system-Capillaries-connect-arteries-and-veins

  • Their wall is very thin, having a tunica intima Capillaries connect arteries and veins.
  • Their wall is very thin, having a tunica intima(also called tunica interna) layer only. They have a large lumen with valves.

Their walls are thin to facilitate the exchange of food material, gases and waste between the blood and the tissues.

Functions of capillaries

  • To allow inward and outward diffusion of glucose, amino acids, urea, etc.
  • To allow diffusion of oxygen into intercellular fluids and inward diffusion of carbon dioxide from intercellular fluids.
  • To allow movement of leucocytes through capillary walls. (RBCs and proteins do not move out of the capillary walls)The-circulatory-system-Differences-between-arteries-and-veins
  • Diagrammatic relationship between arteries, veins and capillaries

3. Veins are the blood vessels that carry blood from the body parts to the heart.

  • All veins (except the pulmonary vein) carry deoxygenated blood.
  • The wall of a vein is thinner as compared to the arterial wall.
  • They have a wider lumen.
  • Blood flows uniformly within veins.
  • Veins have semilunar valves that prevent the backward flow of blood. These valves are formed from folds of the inner walls of the veins. Forward pressure of the blood forces the valve to open and the blood flows towards the heart, whereas the backflow of the blood causes the valve to close.The-circulatory-system-Action-of-a-semilunar-valve-in-a-vein
  • Action of a semilunar valve in a vein
  • Differences between an artery and a vein are given have the power to constrict or dilate as their wall lacks in Table.

The-circulatory-system-Differences-between-arteries-and-veins

Vasodilation and Vasoconstriction

  • The smooth muscle layer of arteries and veins (called the tunica media) has a nervous supply with it. When these nerves are stimulated, the smooth muscles contract, and squeeze
  • the wall of the vessel leading to a narrow lumen. Such a decrease in the lumen size is called vasoconstriction.
  • When the stimulation is removed, the muscle fibres relax and the lumen size increases leading to vasodilation.
  • This clearly indicates the role played by the smooth muscle fibres in the walls of arteries and veins in these
    phenomena. It is to note here, that capillaries do not muscle fibre layer.
  • When we walk in the hot sun, our face turns pink due to vasodilation of the blood vessels supplying blood to the skin capillaries. There is an increase in the flow of blood into the capillaries on the surface of the skin. On the contrary, the skin turns pale due to vasoconstriction when it is too cold.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System The Human Heart

Position, shape and size of the heart

  • The human heart is located between the lungs in the thoracic cavity, with its lower end inclined towards the left. The heart is a hollow, fibromuscular organ and is somewhat conical in shape. It is about the size of one’s fist. It’s pointed end projects to the left.
  • The heart is enclosed by a double-layered membranous sac called the pericardium. It protects the heart from mechanical injury. The space between two pericardial membranes is the pericardial space, which is filled with the pericardial fluid. The pericardial fluid keeps the heart moist and reduces friction between the heart wall membranes. The human heart is made of cardíac muscles or myocardia which contract rhythmically by self-generated impulses.

External structure of the heart

  • The human heart is a four-chambered organ divided by septa into two halves – the right half and the left half. Each half consists of two chambers – the upper, small-sized auricle or atrium and a lower, large-sized ventricle.

The-circulatory-system-Differences-between-closed-circulatory-system-and-open-circulatory-system

 

Internal structure of the heart

  • Internally, the heart has the following main components – four chambers (two auricles and two ventricles), great blood vessels that carry blood to the heart and away from it, and various apertures and valves.

Chambers of the heart

  1. Auricles – The receiving chambers: The auricles or atria are thin-walled chambers and are separated from each other by an inter-auricular septum.
  2. Ventricles – The discharging chambers: The ventricles are thick-walled chambers and are separated from each other by an obliquely placed inter-ventricular septum. The wall of the left ventricle is the thickest because it has to pump blood into vessels, which in turn carry the blood to long distances up to the head, trunk and extremities. The right ventricle pumps blood to the pulmonary arteries, which carry it to the lungs. The walls of the atria are thinner than that of ventricles because they just have to deliver blood into the ventricles.

Great blood vessels of the heart
the blood vessels that enter or leave the heart are called great blood vessels.

Blood vessels entering the heart

1. The right auricle receives blood from three blood vessels.

  • Superior (Anterior) vena cava or Perceval brings deoxygenated blood from the head and upper region of the body.
  • Inferior (Posterior) vena cava or postcaval brings deoxygenated blood from the lower region of the body.
  • Coronary sinus brings deoxygenated blood from the heart’s wall itself into the right auricle.

2. The left auricle receives four blood vessels.

  • Pulmonary veins – The left auricle receives blood from two pairs of pulmonary veins, one pair from each lung. These bring oxygenated blood from the lungs.

Blood vessels leaving the heart

  • Pulmonary artery arises from the right ventricleand carries deoxygenated blood to the lungs for oxygenation.The-circulatory-system-The-location-and-functions-of-major-blood-vessels-of-human-cardiovascular-system
  •  Systemic aorta originates from the left ventricle and supplies oxygenated blood to all body parts, except the lungs.
  • Coronary arteries arise from the base of the aorta. These supply blood to the heart muscles. If coronary arteries get blocked, then it can cause heart attack.

shows the location and functions of major blood vessels of human cardiovascular system.

Apertures and valves in the heart

  • There are four valves in the heart which control the flow of blood within the heart and its passage to various parts of the body through the great blood vessels.
  1. The bicuspid valve (also called the mitral valve or left auriculo-ventricular valve) guards the opening of the left auricle into the left ventricle. This valve consists of two flaps or cusps.
  2. The tricuspid valve (also called the right auriculo- ventricular valve) guards the opening of the right auricle into the right ventricle.
    Both, the bicuspid and the tricuspid valves allow blood to pass from auricles to the ventricles and prevent the backflow of blood.
  3. Semilunar or pulmonary valves are present at the base of the pulmonary artery. These valves allow the flow of blood from the right ventricle to the pulmonary artery and check the backflow of blood into the ventricles.
  4. Aortic semilunar valve is present at the point of origin of the aorta. In all, there are three semilunar valves in the vessels. They allow blood to pass from left ventricle to the aorta and check the return of blood into the ventricles.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System Double Circulation

  • The circulation of blood in the human heart is called double circulation because the blood enters and leaves the heart twice in each heartbeat. Circulation of blood between the heart and body organs (except lungs) is called systemic circulation. Circulation of blood between the heart and the lungs is called pulmonary circulation.

Systemic circulation

  • The left ventricle pumps the oxygenated blood into the systemic aorta. Aorta gives off branches to all the organs of the body except lungs.
  • From these arteries, oxygen is diffused into the tissues. Deoxygenated blood from visceral organs is brought to the right auricle by superior and inferior venae cavae. This part of circulation from the left ventricle to the right auricle of the heart via body tissues (except lungs) is called systemic circulation. 

Pulmonary circulation

  • The circulation of blood from the right ventricle to the left auricle of the heart via lungs is called pulmonary circulation. The right ventricle pumps deoxygenated blood to the lungs for oxygenation. Oxygenated blood from the lungs is returned to the left auricle by four pulmonary veins.

The-circulatory-system-Double-circulation-in-human-heart

The-circulatory-system-Circulation-of-blood-to-various-parts-of-the-body

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System The Human Heart Cardiac Cycle – Systole and Diastole

  • The sequence of events, that take place during the completion of one heartbeat, is known as the cardiac cycle. It involves repeated contraction and relaxation of the heart muscles. A contraction is termed as systole and a relaxation is termed as diastole.
  • One complete heartbeat or cardiac cycle consists of systole and diastole both atria and both ventricles followed by a short pause. It lasts for about 0.8 seconds.
  • The events that take place during the completion of one heartbeat are -the auricular systole, the ventricular systole and the joint diastole or complete cardiac diastole. 

1. Auricular systole: The two auricles act as a pump to force the venous blood into the ventricles. The ventricles are in diastole at this time. During auricular systole, the auricular muscles contract. and the openings of venae cavae and pulmonary vein close. The tricuspid valve and bicuspid valve

The-circulatory-system-a.-Blood-flow-during-cardiac-cycle-b.-Two-main-phases-of-heart-beat

  • open and the blood enters the ventricles through these valves. At the end of an atrial systole, as the two auricles relax, more venous blood is passed from the great veins into the atria to fill them up.

2. Ventricular systole: With the onset of atrial diastole the ventricles start contracting. The bicuspid and tricuspid valves (also known as atrioventricular or AV valves) close to prevent the backward flow of blood from ventricles to the atria. When the pressure in the ventricles increases, semilunar valves open and blood is passed into the great arteries.

3. Joint diastole: At the end of a ventricular systole, the ventricles relax. Also at this stage, the atria are still in their diastole. Since all the heart chambers are in diastole, this stage is called joint diastole. During this phase, blood continues to flow into the auricles from the great veins. As the atria fill with blood, the pressure in them rises and becomes greater than that in the relaxed ventricles. Blood then flows from the auricles to respective ventricles through the AV valves.

How is cardiac cycle conducted?

  • The heart is supplied by a network of nerves but these are not responsible for the initiation of the cardiac cycle.
  • The heart can keep on contracting and relaxing without any stimulation from these nerves. However, the heart.
  • has a regulating system of its own called the conduction system. It is a system of specialised muscle tissue which initiates and spreads the electrical impulses to stimulate a cardiac cycle.

It has the following parts:

  • SA node or sinoatrial node: It is located in the wall of the right atrium near the opening of the superior vena cava. As it initiates each cardiac cycle and sets the pace or rhythm for the heart beat rate, it is called the pacemaker of the heart.
  • AV node or atrioventricular node: It is located near the inferior part of the interauricular septum. The impulses initiated by the SA node make the atria contract and the electrical signals are received by the AV node.
  • AV bundle or atrioventricular bundle: It is a tract of conducting fibres that arise from the AV node and run along the interventricular septum. The impulse travels through these fibres, also called the “Bundle of His”.
  • Purkinje fibres: These fibres emerge from the Bundle of His as branches and spread into the myocardium of ventricles. These fibres stimulate the contraction of ventricles, hence called conduction myofibers.

Electrocardiogram (ECG)

  • The muscle cells or fibres of the heart are specialised at certain parts of the heart to generate electric currents that cause a normal rhythmic heartbeat.

The-circulatory-system-Electrocardiogram-(ECG)

  •  A recording of the electrical events that control the cardiac cycle is called an electrocardiogram (ECG). The instrument used to record the changes is an electrocardiograph.
    The ECG is a useful diagnostic tool for heart diseases like tachycardia (a high pulse rate above 100/minute), bradycardia (a slow pulse rate below 60/minute), ventricular fibrillation and heart block.

Pulse rate

  • The rhythmic contraction of the heart can be felt as a jerk in certain arteries which are superficial in position. This is the arterial pulse. Each ventricular systole starts a new pulse. It proceeds as a wave of expansion throughout the arteries and disappears in the capillaries. The pulse rate is the same as the heartbeat rate. The pulse rate in a normal adult man is about 64-72 beats per minute while in a woman 72-80 beats per minute. The pulse rate in infants is about 140 beats per minute.

Heart sounds – Lubb and dubb

  • The various valves present at the outlet and inlet of ventricles determine the direction of flow of blood in the heart. The opening and closing of these valves cause heart sounds. These sounds can be heard by using a stethoscope (an instrument that magnifies sounds and conducts them to the ear). These sounds are heard as ‘lubb’ and ‘dubb’ sounds.
  • The lubb sound (first heart sound): This sound is caused by the vibrations initiated by the closure of tricuspid and bicuspid valves accompanied by the contraction of ventricular muscles at the start of ventricular systole. It is also called a systolic sound. Lubb sound is low-pitched, not very loud and is of a long duration.
  • The dubb sound (second heart sound): This sound is caused by the closure of the semilunar valves and marks the end of ventricular systole and beginning of ventricular diastole. The dubb sound is high-pitched, louder and shorter in duration.

An abnormal heart sound is called a murmur. This is caused problems with the valves.

The-circulatory-system-Measuring-of-blood-pressure

Blood pressure

  • It is the force with which blood pushes against the walls of the arteries. It is generally measured in terms of how high it can push a column of mercury. When the ventricles contract, the pressure of blood inside the arteries is highest and this pressure is termed as systolic blood pressure.
  • In a healthy young human being, it is about 120 millimetres of mercury (120 mm Hg). When ventricles relax, the pressure of blood inside the arteries is comparatively less and this pressure is termed as diastolic pressure. It is about 80 millimetres of mercury (80 mm Hg) in a healthy young man. Thus, a healthy young man is said to have a normal blood pressure of 120/80 mm of Hg. The instrument used to measure blood pressure is called a sphygmomanometer.
  • Blood pressure =systolic/diastolic = 120/80mm of Hg

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System The Human Heart Portal System

  • A vein that does not carry deoxygenated blood directly to the heart but forms a network of capillaries on another organ before reaching the heart is called a portal vein. It begins and ends in capillaries. The components of the portal vein constitute the portal system. In human beings, two main portal systems – the hepatic and the hypophyseal portal systems are present.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System The Human Heart Hepatic Portal System

  • The venous blood from gastrointestinal organs and spleen is drained into the liver before returning to the heart. Veins from various regions of the gastrointestinal tract and spleen unite to form the hepatic portal vein. It divides into two branches, right and left, which enter into the corresponding liver lobes and break up into capillaries to supply blood. A pair of hepatic veins carry this deoxygenated blood from the liver to the inferior vena cava.

Why is there a need for the hepatic portal system?

  • The blood in hepatic portal vein is rich in nutrients absorbed from the digestive tract. The liver absorbs substances like glucose and stores it as glycogen for use when required. It also modifies other substances so that they can be used by cells. It detoxifies harmful substances in the blood. It also destroys bacteria by phagocytosis.

The-circulatory-system-Arteries-and-veins-associated-with-liver-and-kidney

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System The Human Heart Lymphatic System

  • The lymphatic system comprises a colourless fluid called lymph and a network of fine channels namely, lymphatic capillaries (lacteals) and vessels (ducts), and the lymph nodes.

The-circulatory-system-Lymphatic-system

Lymph

  • Lymph is a colourless fluid. It is a part of the tissue fluid which in turn is a part of blood plasma. So, the composition of tissue fluid and lymph is the same as that of blood plasma but tissue fluid and lymph have lower protein contents.

The-circulatory-system-Differences-between-blood-and-lymph

  • Lymph consists of a fluid matrix in which the white blood corpuscles or leucocytes are present. Unlike blood, lymph does not have red blood corpuscles, platelets and plasma proteins.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System The Human Heart The Circulatory System Functions of The Lymph

The lymph performs many functions.

  • It carries carbon dioxide and nitrogenous waste materials that diffuse into the blood through the tissue fluid.
  • It carries lymphocytes and antibodies from the lymph nodes to the blood.
  • It transports fats (fatty acids and glycerol) from the intestine to the blood.
  • It destroys microorganisms and foreign particles in the lymph nodes.
  • It drains excess tissue fluid from the intercellular spaces back into the blood.
  • It carries the plasma protein macromolecules, synthesized in the and horn endocrine glands to the blood.

Lymph vessels or lymphatics

  • The lymph capillaries join to form the lymphatic vessels. These lymph vessels are like capillaries but have comparatively thin walls and numerous valves. The smaller lymphatic vessels unite to form larger vessels and they unite to form two main lymphatic ducts.
  • The lymph vessels at the right side of the head, neck and the right arm enter into a large vessel, the right lymphatic duct which opens into the right subclavian vein.

Lymph nodes

  • At specific points in the lymph vessels, there are enlargements like beads of a string. These are called lymph nodes. Lymph nodes contain lymphocytes, plasma cells and macrophages. The lymph is filtered through the lymph nodes. The macrophages remove microorganisms and foreign particles from the lymph. The lymphatic nodes also add lymphocytes and antibodies to the lymph from where these are carried to the blood.
  • Lymph nodes are abundant in the regions of neck, armpit and groin.
  • Tonsils and adenoids are masses of lymphatic tissues.

The thymus and spleen are important lymphatic organs of the body.

Tonsils

  • Tonsils are aggregations of lymphatic nodules enclosed by brane. These are located in a ring at the junction of oral cavity and pharynx.

Functions of tonsils

  • Their location is best suited to protect the body against entry of any foreign substance through the oral cavity.
  • They also produce lymphocytes and antibodies.

Spleen

  • Spleen is the largest mass of lymphatic tissue found in our body. It measures about 12 cm in length and is located in the region between the fundus of stomach and diaphragm. It is covered by the peritoneal membrane.The tissue of spleen is of two types:
  1. White pulp – The lymphatic tissue
  2. Red pulp – Sinuses filled with venous blood and tissue cords consisting of macrophages, lymphocytes and granulocytes.

Functions of spleen

  • It produces antibodies, phagocytic cells and destroys dead RBCs and platelets.
  • In embryonic stage, it produces RBCs.
  • It also acts as a reservoir of blood which is released during emergencies such as haemorrhage.

UP Board Notes For Class 10 Science Chapter 8 The Circulatory System The Human Heart Summary

  • The flow of extracellular fluid in the body is called circulation and the organs concerned with this transport form the circulatory system.
  • Human beings have an efficient circulatory system. It consists of:
  • A circulatory medium – blood
  • A system of blood vessels – arteries, veins and capillaries
  • A pumping organ heart.
  • Blood is made up of plasma and cellular elements. The cellular elements include RBCs, WBCs and platelets.
  • Blood does not clot in uninjured vessels due to the presence of a strong, natural anticoagulant called heparin or antithrombin, produced by the liver.
  • The glycoprotein or corpuscle factor present on the surface of RBCs and a protein or the plasma factor present in the blood plasma determine the type of blood group of a person. Blood groups in humans are of four types (A, B, AB, O) in ABO grouping system.
  • Blood of group O can be given to any blood group, hence people with blood group O are called universal donors.
  • Persons with blood group AB can receive blood from all blood groups, hence, are called universal recipients.
  • All arteries carry oxygenated blood, except pulmonary arteries, which carry deoxygenated blood from the heart to the lungs for oxygenation.
  • All veins carry deoxygenated blood except pulmonary veins, which carry oxygenated blood from the lungs to the heart.
  • The human heart is a fibromuscular organ somewhat conical in shape. It is about the size of a fist. Its weight is about 300 g in an adult human being.
  • The human heart is protected by a double-walled membranous sac called pericardium.
  • The human heart is a four-chambered structure, divided by septa Into two halves the right and the left. Each half consists of an upper, small-sized, thin-walled chamber called auricle and a lower, large- sized and thick-walled ventricle.
  • The left auriculo-ventricular aperture is guarded by the bicuspid valve, which consists of two flaps or cusps, and the right auriculo-ventricular aperture is guarded by the tricuspid valve made up of three flaps or cusps. These valves allow blood to pass from auricles to ventricles and also prevent the backward flow of the
    blood.
  • Circulation of blood in the human heart is called double circulation because blood enters and leaves the heart twice. Circulation between the heart and the body organs except lungs is called systemic circulation. Circulation between the heart and the lungs is called pulmonary circulation.
  • The sequence of events that take place during the completion of one heartbeat is known as cardiac cycle. It lasts for about 0.8 seconds.
  • The rhythmic contraction of heart is felt as a jerk in certain arteries that are superficial in position. This is the arterial pulse. The pulse rate of a person is the same as the heartbeat rate.
  • Blood pressure is the force with which blood pushes against the walls of arteries. The blood pressure of a healthy person is 120/80 mm Hg. The instrument used to measure blood pressure is called sphygmomanometer.
  • The lymphatic system comprises of -lymph, lymphatic capillaries and vessels, and lymph nodes.

 

UP Board Notes for Class 10 Science Notes Chapter 7 Control and Coordination

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UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Learning objectives

After completing this chapter, you will be able to:

  • Recognize the need for chemical coordination in plants;
  • Describe various tropic movements in plants.
  • Discuss the role of plant growth regulators;
  • List the major plant hormones and discuss their
    Physiological effects in regulating plant growth:
    • auxins
    • gibberellins
    • cytokinins
    •abscisic acid
    • ethylene

The activities that occur inside our body require proper coordination between the organs. Like animals, plants also need internal coordination for their growth and development. Plants do not have a nervous system, like animals, but they still respond to internal and external changes in the environment around them. Plants can detect changes in light, water, touch, chemicals, and gravity and respond to these changes by the action of hormones. Since plants do not have a nervous system, they use hormones for coordination and response. Therefore, the function of control and coordination in plants is performed by chemical substances called hormones or plant growth regulators.
In this chapter, we shall learn about chemical coordination in plants and how it is brought about.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Stimuli And Receptors

If we accidentally touch any hot object, we immediately withdraw our hands. Thus, we respond to changes in our surroundings. Any change in the environment to which an organism responds and reacts is called a stimulus (plural: stimuli). For example, the leaves of touch-me-not plants fold if we touch (stimulus) them.

Chemical Coordination in plants Touch-me-not plant

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Touch-me-not plant (Mimosa pudica)

Stimuli are detected by a group of cells called receptors. For example, our skin, eyes, ears, nose and tongue contain different receptors. Plants and animals respond to stimuli in a different ways. Animals respond to stimuli in many ways because they have a nervous system.

However, plants react to stimuli in a very limited way because they do not have a nervous system. Thus, response to stimuli is a characteristic property of each living organism.

Plant movements in response to stimuli can be of two types:

  • Tropic movements
  • Nastic movements

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Tropic movements or tropism

The environment has a great influence on a plant’s shape. A growth response that results in the movement of plant parts towards or away from stimuli is called tropism. In simpler terms, the movement of a plant in the direction of a stimulus is known as tropism. It is of two types-positive tropism and negative tropism.

  • When the growing movement of the plant part is towards the stimulus, it is called positive tropism.
  • When the growing movement of the plant part is against or away from the stimulus, it is called negative tropism.

The tropic movements are most commonly found in the radially symmetrical plant parts such as roots and stems.
The tropic movements help the plants to obtain water and nutrients from the soil and light from the sun that are necessary for their growth and survival.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Types Of Tropical Movements In Plants

There are five types of tropical movements in the plants – phototropism, geotropism, hydrotropism, chemotropism and thigmotropism.

1. Phototropism – Movement in response to light.

The growth and movement (orientation) of a plant part in response to the light is called phototropism. For example, movement of sunflowers in the direction of sunlight is phototropism.

If the plant part (like the shoot/stem) orients towards the light then it shows positive phototropism. If the plant part (like its root) moves away from light then it shows negative phototropism.

Chemical Coordination in plants Positive phototropism & Negative phototropism

Positive phototropism             Negative phototropism

The phototropic movements are controlled by growth-regulatory chemical substances (such as auxins) which collect inside the cells farthest away from the light. This causes the plant cells farthest from light to get elongated, leading to an increase in length towards or away from the light source and resulting in curvature.

2. Geotropism – Movement in response to gravity

The growth movement of a plant part in response to gravitational force of the earth is called geotropism. Roots show positive geotropism (grow in the To show phototropism in plants).

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Activity 1

To show phototropism in plants.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Procedure

  • Take a conical flask containing water.
  • Take a few freshly germinated bean seeds and suspend these in the conical flask with the help of a loose wire mesh.
  • Place the flask in the cardboard box as shown on open side of the box should face the source of light.
  • Leave the set-up for 3 days and observe.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination  Observation 1

You will observe that shoots bend towards the light and root away from the light.

  • Now, rotate the flask in such a manner that shoots bend away from the light and roots towards the light. Leave the set-up for a few days and observe.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Observation 2

You will observe that once again shoots turn towards the light and root away from the light.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Conclusion

This shows that the light acts as a stimulus. Shoots respond by bending towards the light (positive phototropism) while roots bend away from the light (negative phototropism).

Chemical Coordination in plants Positive and negative phototropism

Positive and negative phototropism direction of gravity) while shoots show negative geotropism (grow against a force of gravity). This can be observed if you plant a seedling upside down, the roots tend to grow downwards while the shoot will grow upwards.

Chemical-Coordination-in-plants-Positive-and-negative-geotropism

Positive and negative geotropism

3. Hydrotropism – Movement in response to water

The growth movement of plant parts towards water or moisture is called hydrotropism. The roots always grow towards water, therefore roots are positively hydrotropic. For example, the roots of plants growing in humid soil bend towards a higher relative humidity level.

Chemical Coordination in plants Positive-hydrotropism

Positive hydrotropism

4. Chemotropism – Movement in Response to Chemicals

The growth movement of a plant part due to chemical stimuli is called chemotropism. For example, a pollen tube grows through the style towards ovules in response to certain chemical secretions from stigma.

When the plant part grows towards chemical stimulus, it is positive chemotropism. If it grows away from chemicals, it is negative chemotropism.

5. Thigmotropism – Movement in Response to Touch

The growth movement of a plant part in response to the touch of an object is called thigmotropism. In some plants, when the plant organ touches support, it results in a coiling response to catch and hold the object and tighten its hold. For example, the tendrils 88 of a plant (such as sweet peas and vines)

Chemical-Coordination-in-plants-Thigmotropism

Thigmotropism grows towards support, touch it and wind around that support.

Roots have a negative touch response, which means that when they feel an object, they move and grow away from it. This property allows the roots to go through the soil with minimum resistance.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Nastic movements or nasties

The movement of a plant part in response to an external stimulus when occurs in a way that the direction of response is not oriented with respect to the direction of the stimulus, it is called nastic movement.

The curvature so produced in these types of movements is because of diffused stimuli and affects the whole plant uniformly. Nastic movements are temporary movements and plant organs revert after the removal of stimulus.

  • When the non-directional movement of a plant part occurs in response to touch, it is called thigmonasty. For example, movement in touch-me-not plant (Mimosa pudica).
  • When the non-directional movement of a plant part (usually petals) occurs in response to light, it is called photo nasty. For example, opening and closing of Dandelion flower in response to light intensity.

The main difference between tropic and nastic movements is that a tropic movement is directional while a nastic movement is non-directional.

The difference between thigmotropism and thigmonasty is given in Table.

Table. Differences between thigmotropism and thigmonasty

Chemical-Coordination-in-plants-Differences-between-thigmotropism-and-thigmonasty

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination- Plant Growth Regulators

Plants produce certain chemical substances in their cells which regulate their growth and development. These chemicals are secreted in very minute quantities but have a substantial effect on physiological processes in a plant.

Some of these chemicals stimulate plant growth while others retard the rate of growth in plants. Therefore, these chemicals are known as plant growth regulators or plant hormones or phytohormones.

They coordinate the activities of the plants by controlling one or the other aspect of growth of the plants.

Types of plant growth regulators

There are five main types of naturally occurring plant hormones or plant growth regulators.

  1. 1. Auxins
  2. Gibberellins
  3. Cytokinins
  4. Ethylene
  5.  Abscisic acid (ABA)

Auxins

Auxins are a group of plant growth regulators which are synthesized in meristematic tissues at the shoot and root tips. Auxins promote cell enlargement and cell differentiation.

The most common naturally occurring auxin is indole-3-acetic acid (IAA). The common synthetic auxin is indolebutyric acid (IBA). Auxins are widely used in agricultural and horticultural practices due to their role in plant growth.

Functions

1. Influences plant growth: Auxin is a growth hormone and helps the cells to grow longer. It is synthesized at the shoot and root tips. When the tip of a tendril touches a support, the auxin present in it moves away from the support.

Therefore, the side of tendril away from support grows longer and faster. It also curves or bends towards the support and as a result winds around the support.

2. Counter balances root and shoot growth: It has opposite effect on the growth of the stem and roots. It promotes cell growth in shoots and inhibits cell growth in roots.

3. Controls the phototropic behaviour of a plant: When light comes from one side of the plant, auxin diffuses away from the light towards shady side of the shoot. The higher concentration of auxin towards the shady areas stimulates the cells to grow longer and faster and the plant appears to bend towards light.

Chemical-Coordination-in-plants-Auxin-controls-the-phototropic-behaviour-of-a-plant

Auxin controls the phototropic behaviour of a plant

4. Controls the geotropic behaviour of a plant: In a root, extra auxin inhibits growth. In a root, which is growing sideways, more auxin gets accumulated on its lower side. Therefore, the cells on the upper side grow and elongate faster. As a result, the root bends downwards.

Chemical-Coordination-in-plants-Auxin-controls-the-geotropic-behaviour-of-a-plant
Auxin controls the geotropic behaviour of a plant

5. Controls the hydrotropic behaviour of a plant: In a root, more auxin is produced on the side with more moisture. This inhibits the growth on that side and as a result, the root bends towards the moisture.

Chemical-Coordination-in-plants-Auxin-controls-the-hydrotropic-behaviour-of-a-plant

Auxin controls the hydrotropic behaviour of a plant.

6. Induces the formation of seedless fruits without fertilization (known as parthenocarpy) in a number of plants. For example, in tomatoes.

7. Helps in the lengthening of internodes and suppresses the growth of lateral buds.

Gibberellins

Gibberellins are another class of plant growth regulators which produce a variety of physiological responses in plants. These are formed in plastids of leaves of 90 buds, developing embryos and root tips.

At present, more than a hundred different gibberellins have been identified. They are denoted as GA₁, GA₂, GA3 and so on. Of these, gibberellic acid (GA3) is the most thoroughly studied.

Functions

  • Gibberellin promotes cell enlargement in the presence of auxins.
  • It delays leaf senescence in a few species of plants.
  • It promotes cell division and stimulates stem elongation and causes plants to grow taller.
  • It stimulates seed germination by breaking seed dormancy.
  • It also helps in seed germination, flowering and fruit growth.
  • It is used in the brewing industry to speed up the malting process.

Cytokinins

Cytokinins are a kind of plant hormones that play a central role during cell cycle and influence many developmental processes. Natural cytokinins are synthesized in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits, etc.

It also helps to produce new leaves, chloroplasts and lateral shoot growth. Cytokinins are produced in roots and transported up through the xylem. They promote tissue growth, and budding I retard plant senescence.

Functions

  • Cytokinin promotes cell division. Therefore, it is present in high concentrations in areas of rapid cell division like fruits and seeds.
  •  It controls cell enlargement and cell differentiation.
  •  Like gibberellins, it also helps in breaking seed dormancy.

Ethylene

Ethylene is a growth-regulatory gaseous hormone. It is formed in all parts of plants but its synthesis occurs maximum during the ripening of some fruits.

Functions

  • Ethylene is a gaseous hormone that has inhibitory effect on growth.
  • It stimulates abscission in flowers and fruits.
  • It strongly promotes the formation of female flowers in monoecious plants like pumpkin and melon.
  • It induces ripening of fruits.
  • It causes downward curvature of leaves (known as epinasty).
  • It induces flowering in mango.
  • It breaks seed and bud dormancy. It initiates the sprouting of potato tubers and germination in peanut seeds.

Abscisic acid (ABA)

Abscisic acid is a weak acid that was first identified in the early 1960s as a growth inhibitor and was originally believed to be involved in abscission. It is also called a stress hormone as it acts as a mediator in controlling plant responses to environmental stresses. It is produced in mature green leaves and in fruits.

Functions

  • Abscisic acid is a growth-inhibiting hormone and inhibitor of plant metabolism.
  • It promotes wilting of leaves.
  • It promotes the dormancy of seeds and buds. It acts as an inhibitor of seed germination.
  • It prevents loss of water by causing stomatal closure.

UP Board Notes for Class 10 Science Notes Chapter 7 Control And Coordination Summary

  • Plants do not have a nervous system but they still respond to internal and external changes in the environment around them.
  • The function of control and coordination in plants is performed by chemical substances called hormones or plant growth regulators.
  • Any change in the environment to which an organism responds and reacts is called a stimulus. Response to stimuli is a characteristic property of each living organism.
  • Plant movements in response to stimuli can be of two types: tropic movements and nastic movements.
  • A growth response that results in the movement of plant parts towards or away from stimuli is called tropism.
  • When the growing movement of the plant part is towards the stimulus, it is called positive tropism. When the growing movement of the plant part is against or away from the stimulus, it is called negative tropism.
  • There are five types of tropisms found in the plant phototropism, geotropism, hydrotropism, chemotropism and thigmotropism.
  • The growth movement of a plant part in response to the light is called phototropism.
  • The growth movement of a plant part in response to gravitational force of the earth is called geotropism.
  • The growth movement of a plant part towards water or moisture is called hydrotropism.
  • The growth movement of a plant part due to chemical stimuli is called chemotropism.
  • The growth movement of a plant part in response to the touch of an object is called thigmotropism.
  • The movement of a plant part in response to an external stimulus when occurs in a way that the direction of response is not based on the direction of stimulus, it is called nastic movement.
  • Plants produce certain chemical substances in their cells which regulate their growth and development. These chemicals are known as plant growth regulators or plant hormones or phytohormones.
  • Auxin is a growth hormone and helps the cells to grow longer, and controls the phototrophic and the geotropic behaviour of a plant.
  • Gibberellin promotes cell enlargement, and cell division and stimulates stem elongation
  • Cytokinins play a central role during the cell cycle and influence numerous developmental programmes.
  • Ethylene is a gaseous hormone that has an inhibitory effect on growth and induces ripening of fruits.
  • Abscisic acid is a growth-inhibiting hormone and inhibitor of plant metabolism. It promotes wilting of leaves.