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CBSE NOTES CLASS 10 SCIENCE CHAPTER 7

CONTROL AND COORDINATION

Coordination

Stimuli

Response

Need for control and coordination

Control & coordination in animals (human)

Nervous system

Sense organs

Receptors

Effectors

Motor nerves

Relay neurons

Nerve Cell or Neuron

Synapse

Parts of nervous systems

Central nervous system

Peripheral nervous system

Reflex action

Reflex arc

Human brain

Parts of human brain

Forebrain or cerebrum

Midbrain or hypothalamus

Hind brain

Cerebellum

Medulla

Pons

Spinal cord

Protection of the brain & the spinal cord

Glands

Exocrine glands

Endocrine glands

Endocrine vs exocrine glands

Hormones

Endocrine System

Glands which act as both endocrine & exocrine

Important glands & hormones secreted

Iodine is necessary

Insulin and diabeties

Feedback mechanism

Comparision of nerveous system and endocrine system

Coordination in plants

Movement in Plants

Positive Tropism

Negative Tropism

Geotropic Movement

Phototropic Movement

Hydrotropic Movement

Thigmotropic Movement

Nastic Movement

Thigmonastic Movements

Photonastic Movements

CBSE NOTES CLASS 10 SCIENCE CHAPTER 7

CONTROL AND COORDINATION

Coordination

The working together of various organs of the body of an organism in a proper manner to produce appropriate reaction to a stimulus is called coordination.

Stimuli

The changes in the environment to which organisms respond and react are called Stimuli (Singular Stimulus).

Response

The response of an organism to stimulus is usually in the form of some movement of body parts.

Examples of Stimulus and Response

If we touch a very hot object accidently, we quickly pull our hand away from the hot object.

Here the stimulus is heat and movement of hand is response.

Need for Control and Coordination

A living organism does not live in isolation. It has to constantly interact with its external environment and has to respond properly for its survival. For example; when a hungry lion spots a deer, the lion has to quickly make a move so that it can have its food. On the other hand, the deer needs to quickly make a move to run for its life.

CONTROL & COORDINATION IN ANIMALS (HUMAN)

Control and coordination in animals takes place by

(i) Nervous system &

(ii) Endocrine system.

NERVOUS SYSTEM

Sense organs

There are five sense organs in human beings (and other higher animals) – eyes, ears, nose, tongue, skin.

Receptor

A receptor is a cell or group of cells in the sense organs which is sensitive to a particular type of stimulus or change in the environment.

The change could be light, sound, smell, taste, heat, pressure, touch, etc.

There are different types of receptors in different sense organs,

  1. Photo-receptors detect light and are present in eyes.

  2. Phono-receptors detect sound and are present in ears.

  3. Olfactory-receptors detect smell and are present in the nose.

  4. Gustatory-receptors detect taste and are present in the tongue.

  5. Thermo-receptors (for heat and cold) and baro-receptors (for pressure) are present in the skin.

The receptors in the sense organs receive the stimuli from external environment and send the messages to the brain or spinal cord in the form of electrical impulses through sensory nerves.

Effectors

Effectors are organs capable of responding to a stimuli according to the instructions sent to them from the nervous system. They are normally like muscles or glands.

Motor Nerves

These are the nerves which transmit the response from the brain and spinal cord to the effectors in the form of electrical impulses.

Relay neurons are found between sensory input neurons and motor output/response neurons. Relay neurons are found in the brain and spinal cord and allow sensory and motor neurons to communicate.

It is autonomic or involuntary.

Nerve Cell or Neuron

Nerve cells or neurons are the structural and functional unit of nervous system. It is the longest cell in the body.

A neuron has three components,

Cell body of neuron contains cytoplasm and nucleus.

There are a number of short and long fibres attached to the cell body. The shorter fibres are called dendrites and the longest is called axon. The axon also has a protective and insulating sheath (cover) around it, which is made of myelin (made of fat and protein).

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The dendrites pick up the nerve impulse (messages from the receptors). The information, acquired at the end of the dendritic tip of a nerve cell sets off a chemical reaction that creates an electrical impulse.

The impulse travels from the dendrite to the cell body, and then along the axon to its end.

At the end of the axon, the electrical impulse sets off the release of some chemicals.

Synapse

Space/junction between two adjacent nerves is called Synapse. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. Synapse actually works like a one way valve, as the chemical is present only on one side of the synapse.

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The cycle keeps repeating till the signal reaches the brain or spinal cord.

Parts of Nervous Systems

In consists of two main parts,

(i) The central nervous system (CNS) containing brain and spinal cord, and

(ii) The peripheral nervous system (PNS), containing all other nerves of the body.

Human Brain

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Brain is the highest coordinating centre in the body.

Human brain is a highly complex organ, which is composed of highly folded nervous tissue to accommodate a larger surface area in less space.

The brain is protected by a bony box called cranium.

The brain is surrounded by three membranes called meninges.

The space between the meninges is filled by cerebro spinal fluid (CSF), which provides cushion to the brain against mechanical shocks.

Parts of Human Brain

Spinal cord

Functions of Spinal Cord

Protection of the brain & the spinal cord

The space between the meninges is filled by cerebro-spinal fluid (CSF), which provides cushion against mechanical shocks.

WORKING OF NERVOUS SYSTEM

When the sense organ detects a stimulus, it sends the message to the brain and spinal cord in the form of electrical impulses through the sensory neurons. The brain/spinal cord sends out instructions to the concerned body part (effector) for taking necessary action through motor nerves. The effector then acts according to the instruction.

For thinking and complicated responses, both brain and spinal cord are involved, but in case of simple responses, only spinal cord is involved.

Reflex Action

A reflex action is an involuntary and spontaneous, involuntary and automatic response to a stimulus. Reflex action is not under the voluntary control of brain.

For example, on touching a hot object unknowingly we instantly withdraw our hand.

Reflex Arc

The pathway of the reflex action or the path taken by nerve impulses in the reflex action is called reflex arc.

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Spinal Reflexes

Those reflexes which involve only the spinal cord are called spinal reflexes.

Cerebral Reflexes

Those reflexes which involve the brain are called cerebral reflexes. Organs involving cerebral reflexes are actually present in the head, for example eye.

GLANDS

A gland is a structure which secretes specific substances in the body. There are two types of glands

(i) Exocrine glands – The glands which secrete the juices into a duct or tube are called exocrine glands. Example – salivary glands.

(ii) Endocrine glands – The glands are ductless and secrete the juices directly in the blood. Example – pituitary gland.

ENDOCRINE VS EXOCRINE GLANDS

S. No

Endocrine glands

Exocrine glands

1.

Ducts absent

Ducts present

2.

Secrete hormones

Secrete enzymes

3.

Secreted in blood

Secreted in ducts of glands

4.

Situated away from the site of action

Situated near the site of action

Hormones

Hormones are chemical substances secreted in very small amounts by specialized tissues in the body called endocrine glands.

Endocrine System

The endocrine system is composed of several endocrine glands.

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SOME GLANDS WHICH ACT AS BOTH ENDOCRINE & EXOCRINE

Gland

Endocrine function

Exocrine function

Pancreas

Produces Insulin & Glucagon hormones.

Produces digestive enzyme. (pancreatic amylase)

Testes

Produces Testosterone hormone.

Produces male gametes (reproductive cells)

Ovaries

Produces Oestrogen & Progestrone hormones.

Produces female gametes (reproductive cells)

IMPORTANT GLANDS & HORMONES SECRETED

Endocrine gland

Location

Hormones Produced

Functions

Hypothalamus

Brain

Releasing and Inhibiting Hormone

Controls the release of hormones from pituitary gland.

Pituitary gland

At the base of brain

Growth hormone (GH)

GH stimulates growth,

Thyroid Stimulating Hormone (TSH)

TSH stimulates functioning of thyroid gland,.

Follicle Stimulating Hormone (FSH)

FSH stimulates the follicles during ovulation

Thyroid gland

Neck

Thyroxine

Controls general metabolism and growth in the body.

Parathyroid gland

Embedded in thyroid gland

Parathormone

Regulates Calcium and phosphate levels in the blood

Thymus

Lower part of neck /upper part of chest

Thymus

Development of immune system

Adrenal gland

Above kidneys

Adrenalin

Prepares the body for emergency situations and hence is also called ‘Fight and flight’ hormone.

Pancreas

Near stomach

Insulin

Lowers blood sugar level

Glucagon

Increases blood sugar level

Testes (male)

In scrotum

Testosterone

Produces male gametes, Development of secondary sexual characters during puberty.

Ovary (female)

Near uterus

Oestrogen

Produces female gametes, Development of secondary sexual characters during puberty.

Progestrone

Mensural cycle & Maintains pregnancy

Pineal

Deep in the centre of the brain.

Melatonine

Helps maintain circadian rhythem and reproductive harmones.

COMPARISION OF NERVEOUS SYSTEM AND ENDOCRINE SYSTEM

S. No.

Nervous System

Hormonal Control

1

Nerve cells are involved.

Endocrine glands are involved.

2

The messages are transmitted in the form of electrical impulses.

The messages are transmitted in the form of chemicals (hormones).

3

Flow of information is rapid and the response time is very short.

Flow of information is slow and the response time is longer.

4

Nerve impulses are not specific in their action.

Each hormone has specific actions.

5

Effect of messages usually lasts for very short time.

Effect of messages usually lasts longer.

COORDINATION IN PLANTS

Unlike animals, plants do not have a nervous system. Plants use chemical means for control and coordination. Many plant hormones are responsible for various kinds of movements in plants.

PLANT HORMONES (PHYTOHORMONES)

S. No.

Name of Hormone

Function

1

Auxins

Help in growth of root & shoot tips, cell enlargement snd cell differentiation, fruit growth.

2

Gibberellins

Help in vegetative growth, breaking of seed dormancy and promote germination

3

Cytokinins

Promote cell division, breaking of seed dormancy and promote germination

4

Ethylene

Ripening and rotting of fruits

5

Abscissic acid

Inhibits growth & causes wilting (falling) of leaves, promotes seed dormancy, closing stomata

Movement in Plants

Movements in plants can be divided into two main types, viz. tropic movement and nastic movement.

Tropic Movement

The movements which are in a particular direction in relation to the stimulus are called tropic movements. Tropic movements happen as a result of growth of a plant part in a particular direction.

Positive Tropism: The movements of plants in the direction of stimulus, is called positive tropism.

Negative Tropism: The movements of plants in the direction away from the stimulus, is called negative tropism.

Different Types of Tropism

There are four types of tropic movements, viz. geotropic, phototropic, hydrotropic and thigmotropic.

Nastic Movement

The movements which do not depend on the direction from the stimulus acts are called nastic movement.

Thigmonastic Movements

When someone touches the leaves of mimosa (chhui mui – touch me not), the leaves droop. The drooping is independent of the direction from which the leaves are touched. This is done by plant cells by changing the amount of water in leaves. This is example of thigmonastic movement.

Photonastic Movements

Dendelion flower opens the petals in bright light during day time and closes the petals at dusk at dark.

Moonflower opens the petals at dusk when it is dark and no light and closes the petals during the day time when there is bright light.

Nastic movements happen because of changing water balance in the cells. When leaves of mimosa are touched, the cells in the leaves lose water and become flaccid, resulting in drooping of leaves.