Control and Coordination by ACHARAYAZ Notes - Class 10 PDF Download

 Page 1


 
 
CONTROL AND COORDINATION
Control 
The word control means to keep a check on the working of the 
organs in case of living organisms. It also means to make the 
organs work according to the requirement. 
 
Coordination 
The working together of the various organs of an organism in 
a systematic manner so as to produce a proper reaction to the 
stimulus is called coordination. 
 
Stimulus  
The change in the environment to which the organisms 
respond and react is called stimulus (plural stimuli). The 
reaction to the stimulus is a characteristic property of living 
organisms. Examples of stimuli are light, heat, cold sound, 
smell, taste, touch, pressure, water and force of gravity etc. 
The response of an organism to a stimulus is generally in the 
form of some movement of the body part. The animals can 
react to stimuli in many different ways. The plants react to 
stimuli in a very limited way. 
 
Control And Coordination In Plants 
Control and Coordination is done in plants by only one system 
i.e., Hormonal System. The hormones working inside plants 
are called phytohormones. The plants coordinate their 
behaviours against environmental changes by using hormones. 
The plants respond to various stimuli very slowly by growing. 
It usually takes a considerable time to observe the affect of 
stimulus on a plant. Plants can sense the presence of stimuli 
like light, gravity, chemicals, water etc. and respond to them. 
 
Plant Hormones (Phytohormones) 
There are five major types of plants hormones: - 
1. Auxins 
2. Gibberellins 
3. Cytokinins 
4. Absicic Acid (ABA)   
5. Ethylene (or Ethene) 
 
1. Auxins 
1. Promote cell enlargement and cell differentiation. 
2. Promote cell division. 
3. Promote fruit growth. 
4. Promote root initiation & flower initiation. 
5. Control geotropic behaviour. 
6. Stimulate respiration. 
7. Promote reproductive processes. 
8. Prevent leaf and fruit fall. 
 
2. Gibberellins 
1. Promote cell enlargement and cell division.  
2. Help in breaking dormancy in seeds and buds. 
3. Promote flowering. 
4. Increase cell size. 
5. Induce germination in dark. 
6. Counter act the effect of growth inhibitors. 
7. Promote growth in fruits. 
8. Prevent ageing of leaves.  
 
3. Cytokinins 
1. Promote cell division. 
2. Help in breaking the dormancy of seeds and buds. 
3. Delay the ageing of leaves. 
4. Promote the opening of stomata. 
5. Delay senescence (ageing). 
6. Provide resistance to plants against very high and low 
temperature from injuries. 
7. Provide nutrient transport. 
8. Enhances rate of synthesis of chlorophyll. 
 
4. Abscisic Acid (ABA) 
1. Inhibits growth and retards the developmental processes. 
2. Accelerates senescence. 
3. Promotes falling of leaves (abscission). 
4. Promotes stomata closure. 
5. It inhibits seed germination. 
6. It provides resistance against cold. 
7. Inhibits the synthesis of RNA and proteins. 
8. Promotes dormancy in seeds and buds. 
 
5. Ethylene (Ethane)  
1. Inhibits longitudinal growth. 
2. Inhibits the growth of roots and development of lateral 
buds. 
3. Promotes turning of leaves yellow and shedding of plant. 
4. Promotes ripening of fruit. 
5. Promotes flowering. 
6. Promotes breaking dormancy in several plant organs. 
7. Accelerates abscission of leaves, flowers and fruits. 
8. Someway lowers the auxin level in the tissue thus makes 
the stem ageotropic. 
 
Plant Movements 
The movement in any part of a plant is usually a growth 
movement. The movements in plant parts are caused by an 
unequal growth in roots and shoots by the action of 
hormones, under the influence of stimulus. 
 
Tropism 
The movement of a part of a plant in response to an external 
stimulus is called tropism. It is a directional movement of part 
of a plant caused by its growth. The growth of a plant part in 
response to a stimulus can be towards the stimulus (positive 
tropism) or away from the stimulus (negative tropism). 
 
Types Of Tropism 
1. Phototropism 
2. Geotropism 
3. Chemotropism 
4. Hydrotropism 
 
1. Phototropism 
The movement of a part of the plant in response to light is 
called phototropism. 
Example 
 
Page 2


 
 
CONTROL AND COORDINATION
Control 
The word control means to keep a check on the working of the 
organs in case of living organisms. It also means to make the 
organs work according to the requirement. 
 
Coordination 
The working together of the various organs of an organism in 
a systematic manner so as to produce a proper reaction to the 
stimulus is called coordination. 
 
Stimulus  
The change in the environment to which the organisms 
respond and react is called stimulus (plural stimuli). The 
reaction to the stimulus is a characteristic property of living 
organisms. Examples of stimuli are light, heat, cold sound, 
smell, taste, touch, pressure, water and force of gravity etc. 
The response of an organism to a stimulus is generally in the 
form of some movement of the body part. The animals can 
react to stimuli in many different ways. The plants react to 
stimuli in a very limited way. 
 
Control And Coordination In Plants 
Control and Coordination is done in plants by only one system 
i.e., Hormonal System. The hormones working inside plants 
are called phytohormones. The plants coordinate their 
behaviours against environmental changes by using hormones. 
The plants respond to various stimuli very slowly by growing. 
It usually takes a considerable time to observe the affect of 
stimulus on a plant. Plants can sense the presence of stimuli 
like light, gravity, chemicals, water etc. and respond to them. 
 
Plant Hormones (Phytohormones) 
There are five major types of plants hormones: - 
1. Auxins 
2. Gibberellins 
3. Cytokinins 
4. Absicic Acid (ABA)   
5. Ethylene (or Ethene) 
 
1. Auxins 
1. Promote cell enlargement and cell differentiation. 
2. Promote cell division. 
3. Promote fruit growth. 
4. Promote root initiation & flower initiation. 
5. Control geotropic behaviour. 
6. Stimulate respiration. 
7. Promote reproductive processes. 
8. Prevent leaf and fruit fall. 
 
2. Gibberellins 
1. Promote cell enlargement and cell division.  
2. Help in breaking dormancy in seeds and buds. 
3. Promote flowering. 
4. Increase cell size. 
5. Induce germination in dark. 
6. Counter act the effect of growth inhibitors. 
7. Promote growth in fruits. 
8. Prevent ageing of leaves.  
 
3. Cytokinins 
1. Promote cell division. 
2. Help in breaking the dormancy of seeds and buds. 
3. Delay the ageing of leaves. 
4. Promote the opening of stomata. 
5. Delay senescence (ageing). 
6. Provide resistance to plants against very high and low 
temperature from injuries. 
7. Provide nutrient transport. 
8. Enhances rate of synthesis of chlorophyll. 
 
4. Abscisic Acid (ABA) 
1. Inhibits growth and retards the developmental processes. 
2. Accelerates senescence. 
3. Promotes falling of leaves (abscission). 
4. Promotes stomata closure. 
5. It inhibits seed germination. 
6. It provides resistance against cold. 
7. Inhibits the synthesis of RNA and proteins. 
8. Promotes dormancy in seeds and buds. 
 
5. Ethylene (Ethane)  
1. Inhibits longitudinal growth. 
2. Inhibits the growth of roots and development of lateral 
buds. 
3. Promotes turning of leaves yellow and shedding of plant. 
4. Promotes ripening of fruit. 
5. Promotes flowering. 
6. Promotes breaking dormancy in several plant organs. 
7. Accelerates abscission of leaves, flowers and fruits. 
8. Someway lowers the auxin level in the tissue thus makes 
the stem ageotropic. 
 
Plant Movements 
The movement in any part of a plant is usually a growth 
movement. The movements in plant parts are caused by an 
unequal growth in roots and shoots by the action of 
hormones, under the influence of stimulus. 
 
Tropism 
The movement of a part of a plant in response to an external 
stimulus is called tropism. It is a directional movement of part 
of a plant caused by its growth. The growth of a plant part in 
response to a stimulus can be towards the stimulus (positive 
tropism) or away from the stimulus (negative tropism). 
 
Types Of Tropism 
1. Phototropism 
2. Geotropism 
3. Chemotropism 
4. Hydrotropism 
 
1. Phototropism 
The movement of a part of the plant in response to light is 
called phototropism. 
Example 
 
 
Stem or shoot of a plant bends towards the light is a positive 
phototropism. Roots of a plant moves away from light is called 
negative phototropism. The plant shoots respond to light and 
bend towards it due to action of auxin hormone. This happens 
as follows:- 
 
              
1.  When the sunlight falls from above, the auxin hormone 
present on the tip of the stem spreads uniformly down the 
stem. Due to the equal presence of auxin both the sides 
of the stem grows equally rapidly and grows straight. 
2. When the light falls on only one side of the stem then the 
auxin hormone collects on the opposite side (shady side) 
because auxin hormone prefers to stay in shade. 
3. Now more auxin hormone is present on one side but not 
on the other. Due to this one side of stem where auxin is 
present grows faster than the other side where there are 
no auxins. Since one side of the stem grows faster and 
becomes bigger than the other therefore the stem bends 
towards the other side (weaker side which lacks auxins). 
 
2. Geotropism 
The response of a plant to gravity is called geotropism  
 
Example 
The roots of a plant always grow down in response to gravity 
(positive geotropism). Shoots of a plant always grow up away 
from the pull of gravity (negative geotropism). This can be 
shown as follows:- 
 
1. When a potted plant growing in a transparent jar is kept 
in a normal position we can see its roots growing down 
wards and stem growing upwards. 
2.  Now if pot is tilted and kept in horizontal direction the 
roots and stem both are parallel to the ground. After a 
few days we will find that roots of this potted plant bend 
downwards and shoot upwards showing the effect of 
geotropism. 
 
3. Chemotropism 
The growth or movement of the part of a plant due to a 
chemical stimulus is called chemotropism.   
Example 
The growth or movement of a pollen tube towards the ovule is 
induced by stimulus of a sugary substance. The stigma of the 
carpel of a flower secretes a chemical (sugary substance) into 
the style towards the ovary.  The sugary substance acts as a 
stimulus for the pollen grains which fall on the stigma of the 
carpel. The pollen grains respond to this stimulus by growing a 
pollen tube in the downward direction into the style of the 
carpel and reaches to the ovule in the ovary. 
 
4. Hydrotropism 
The response of a plant towards the stimulus of water is called 
hydrotropism. 
Example 
The roots of the plant always show positive hydrotropism 
whereas the shoot of the plant always show negative 
hydrotropism. 
 
Nastic Movements 
The movement of a plant part in response to a stimulus which 
takes place in any direction neither towards the stimulus nor 
away from the stimulus is called nastic movement. The nastic 
movements of plants are induced by stimuli such as heat, 
light, touch (or contact) etc. The direction of nastic movement 
is not determined by the direction from which the stimulus is 
applied. Nastic movements are mostly exhibited by flat organs 
of the plants like leaves and petals of a flower. 
 
 
Page 3


 
 
CONTROL AND COORDINATION
Control 
The word control means to keep a check on the working of the 
organs in case of living organisms. It also means to make the 
organs work according to the requirement. 
 
Coordination 
The working together of the various organs of an organism in 
a systematic manner so as to produce a proper reaction to the 
stimulus is called coordination. 
 
Stimulus  
The change in the environment to which the organisms 
respond and react is called stimulus (plural stimuli). The 
reaction to the stimulus is a characteristic property of living 
organisms. Examples of stimuli are light, heat, cold sound, 
smell, taste, touch, pressure, water and force of gravity etc. 
The response of an organism to a stimulus is generally in the 
form of some movement of the body part. The animals can 
react to stimuli in many different ways. The plants react to 
stimuli in a very limited way. 
 
Control And Coordination In Plants 
Control and Coordination is done in plants by only one system 
i.e., Hormonal System. The hormones working inside plants 
are called phytohormones. The plants coordinate their 
behaviours against environmental changes by using hormones. 
The plants respond to various stimuli very slowly by growing. 
It usually takes a considerable time to observe the affect of 
stimulus on a plant. Plants can sense the presence of stimuli 
like light, gravity, chemicals, water etc. and respond to them. 
 
Plant Hormones (Phytohormones) 
There are five major types of plants hormones: - 
1. Auxins 
2. Gibberellins 
3. Cytokinins 
4. Absicic Acid (ABA)   
5. Ethylene (or Ethene) 
 
1. Auxins 
1. Promote cell enlargement and cell differentiation. 
2. Promote cell division. 
3. Promote fruit growth. 
4. Promote root initiation & flower initiation. 
5. Control geotropic behaviour. 
6. Stimulate respiration. 
7. Promote reproductive processes. 
8. Prevent leaf and fruit fall. 
 
2. Gibberellins 
1. Promote cell enlargement and cell division.  
2. Help in breaking dormancy in seeds and buds. 
3. Promote flowering. 
4. Increase cell size. 
5. Induce germination in dark. 
6. Counter act the effect of growth inhibitors. 
7. Promote growth in fruits. 
8. Prevent ageing of leaves.  
 
3. Cytokinins 
1. Promote cell division. 
2. Help in breaking the dormancy of seeds and buds. 
3. Delay the ageing of leaves. 
4. Promote the opening of stomata. 
5. Delay senescence (ageing). 
6. Provide resistance to plants against very high and low 
temperature from injuries. 
7. Provide nutrient transport. 
8. Enhances rate of synthesis of chlorophyll. 
 
4. Abscisic Acid (ABA) 
1. Inhibits growth and retards the developmental processes. 
2. Accelerates senescence. 
3. Promotes falling of leaves (abscission). 
4. Promotes stomata closure. 
5. It inhibits seed germination. 
6. It provides resistance against cold. 
7. Inhibits the synthesis of RNA and proteins. 
8. Promotes dormancy in seeds and buds. 
 
5. Ethylene (Ethane)  
1. Inhibits longitudinal growth. 
2. Inhibits the growth of roots and development of lateral 
buds. 
3. Promotes turning of leaves yellow and shedding of plant. 
4. Promotes ripening of fruit. 
5. Promotes flowering. 
6. Promotes breaking dormancy in several plant organs. 
7. Accelerates abscission of leaves, flowers and fruits. 
8. Someway lowers the auxin level in the tissue thus makes 
the stem ageotropic. 
 
Plant Movements 
The movement in any part of a plant is usually a growth 
movement. The movements in plant parts are caused by an 
unequal growth in roots and shoots by the action of 
hormones, under the influence of stimulus. 
 
Tropism 
The movement of a part of a plant in response to an external 
stimulus is called tropism. It is a directional movement of part 
of a plant caused by its growth. The growth of a plant part in 
response to a stimulus can be towards the stimulus (positive 
tropism) or away from the stimulus (negative tropism). 
 
Types Of Tropism 
1. Phototropism 
2. Geotropism 
3. Chemotropism 
4. Hydrotropism 
 
1. Phototropism 
The movement of a part of the plant in response to light is 
called phototropism. 
Example 
 
 
Stem or shoot of a plant bends towards the light is a positive 
phototropism. Roots of a plant moves away from light is called 
negative phototropism. The plant shoots respond to light and 
bend towards it due to action of auxin hormone. This happens 
as follows:- 
 
              
1.  When the sunlight falls from above, the auxin hormone 
present on the tip of the stem spreads uniformly down the 
stem. Due to the equal presence of auxin both the sides 
of the stem grows equally rapidly and grows straight. 
2. When the light falls on only one side of the stem then the 
auxin hormone collects on the opposite side (shady side) 
because auxin hormone prefers to stay in shade. 
3. Now more auxin hormone is present on one side but not 
on the other. Due to this one side of stem where auxin is 
present grows faster than the other side where there are 
no auxins. Since one side of the stem grows faster and 
becomes bigger than the other therefore the stem bends 
towards the other side (weaker side which lacks auxins). 
 
2. Geotropism 
The response of a plant to gravity is called geotropism  
 
Example 
The roots of a plant always grow down in response to gravity 
(positive geotropism). Shoots of a plant always grow up away 
from the pull of gravity (negative geotropism). This can be 
shown as follows:- 
 
1. When a potted plant growing in a transparent jar is kept 
in a normal position we can see its roots growing down 
wards and stem growing upwards. 
2.  Now if pot is tilted and kept in horizontal direction the 
roots and stem both are parallel to the ground. After a 
few days we will find that roots of this potted plant bend 
downwards and shoot upwards showing the effect of 
geotropism. 
 
3. Chemotropism 
The growth or movement of the part of a plant due to a 
chemical stimulus is called chemotropism.   
Example 
The growth or movement of a pollen tube towards the ovule is 
induced by stimulus of a sugary substance. The stigma of the 
carpel of a flower secretes a chemical (sugary substance) into 
the style towards the ovary.  The sugary substance acts as a 
stimulus for the pollen grains which fall on the stigma of the 
carpel. The pollen grains respond to this stimulus by growing a 
pollen tube in the downward direction into the style of the 
carpel and reaches to the ovule in the ovary. 
 
4. Hydrotropism 
The response of a plant towards the stimulus of water is called 
hydrotropism. 
Example 
The roots of the plant always show positive hydrotropism 
whereas the shoot of the plant always show negative 
hydrotropism. 
 
Nastic Movements 
The movement of a plant part in response to a stimulus which 
takes place in any direction neither towards the stimulus nor 
away from the stimulus is called nastic movement. The nastic 
movements of plants are induced by stimuli such as heat, 
light, touch (or contact) etc. The direction of nastic movement 
is not determined by the direction from which the stimulus is 
applied. Nastic movements are mostly exhibited by flat organs 
of the plants like leaves and petals of a flower. 
 
 
 
 
Example 
Mimosa plant (touch-me-not) shows nastic movement. If we 
touch the leaves of a mimosa plant with our finger then all its 
leaves fold up and droop. A number of flowers mainly of the 
daisy family, close up when light fades in the evening and re-
open the next day when light appears. This is an example of 
nastic movement. The stimulus in this case is light. 
 
Coordination in Animals 
The multicellular animals (except sponges) have specialized 
cells called nerve cells to respond to stimuli and coordinate 
their activities. 
 
Nervous System 
Nervous system is a system of neurons/nerve cells, nerves and 
nervous organs that coordinate and control the activities of 
different parts of an animal body by receiving and sending 
nerve impulses. 
 
Functions Of Nervous System 
1. Making the animal aware of the environment. 
2. Receiving information about the changes in the 
environment, processing and responding them. 
3. Memory of past experiences and expressions. 
4. Interpretation of external changes with the help of 
memory. 
5. Producing sensation like pain, pleasure, smell, taste, 
vision, hearing etc. with the help of special sense organs. 
6. Linking different body parts and coordinating their 
functions. 
7. Controlling activities of muscles and glands.  
8. Knowing changes or disturbances in the interior of the 
body.  
9. Taking immediate remedial action for harmful sensations 
without consulting will of animals.  
10. It is control system for all our actions, thinking & 
behaviour.  
11. Coordinate involuntary processes of our body like heart 
beat and breathing etc.  
12. It acts like a manager inside animal’s body. 
 
Control And Coordination In Higher Animals 
The complete control and coordination in higher animals 
occurs due to the combined action of both nervous system and 
endocrine system (hormonal system) together called 
neuroendocrine system. 
 
Receptor 
 A receptor is a cell or a group of cells which are sensitive to a 
particular type of stimulus. There are certain types of 
receptors like:- 
Thermo receptors  :  For heat 
Photoreceptors  :  For light 
Phonoreceptors   :  For sound 
Olfactory receptors  :  For smell 
The receptors are a kind of sense organs. The receptors 
collect the information from around the animal and send it to 
brain or spinal cord through sensory neurons. Motor neurons 
then transmit the response from brain or spinal cord to the 
effector organs. 
 
Effector 
The part of body which responds to the stimulus is called 
effector.  Effectors are mainly the muscles and glands. 
 
Control And Coordination In Humans 
In human beings the complete control and coordination occurs 
due to the combined action of two systems: - 
1. Nervous System 
2. Endocrine System 
That is why it is called neuroendocrine system. 
 
Human Nervous System 
 
The Fundamental Unit Of Nervous System – Neuron 
A neuron is the structural and functional unit of nervous 
system. Nervous system is thus made up of special cells called 
neurons. Neuron is the largest cell in the body. The neurons 
carry messages in the form of electrical signals called nerve 
impulses over large distances in the body quickly. 
 
Components Of Neuron   
1. Cell Body 
2. Dendrites 
3. Axon 
 
Cell Body 
It is like a typical animal cell which contains cytoplasm and a 
nucleus. A number of long and thin nerve fibers stretch out 
from the cell body of a neuron. 
 
Dendrites 
The shorter fibers on the body of a neuron are called 
dendrites. The dendrites pick up the nerve impulses from near 
by neurons and pass to cell body. 
 
Axon 
The longest fibre on a cell body of a neuron is called axon. 
The axon has an insulating and protective sheath (or cover) of 
myelin (made up of fats and proteins) around it. The axon 
 
Page 4


 
 
CONTROL AND COORDINATION
Control 
The word control means to keep a check on the working of the 
organs in case of living organisms. It also means to make the 
organs work according to the requirement. 
 
Coordination 
The working together of the various organs of an organism in 
a systematic manner so as to produce a proper reaction to the 
stimulus is called coordination. 
 
Stimulus  
The change in the environment to which the organisms 
respond and react is called stimulus (plural stimuli). The 
reaction to the stimulus is a characteristic property of living 
organisms. Examples of stimuli are light, heat, cold sound, 
smell, taste, touch, pressure, water and force of gravity etc. 
The response of an organism to a stimulus is generally in the 
form of some movement of the body part. The animals can 
react to stimuli in many different ways. The plants react to 
stimuli in a very limited way. 
 
Control And Coordination In Plants 
Control and Coordination is done in plants by only one system 
i.e., Hormonal System. The hormones working inside plants 
are called phytohormones. The plants coordinate their 
behaviours against environmental changes by using hormones. 
The plants respond to various stimuli very slowly by growing. 
It usually takes a considerable time to observe the affect of 
stimulus on a plant. Plants can sense the presence of stimuli 
like light, gravity, chemicals, water etc. and respond to them. 
 
Plant Hormones (Phytohormones) 
There are five major types of plants hormones: - 
1. Auxins 
2. Gibberellins 
3. Cytokinins 
4. Absicic Acid (ABA)   
5. Ethylene (or Ethene) 
 
1. Auxins 
1. Promote cell enlargement and cell differentiation. 
2. Promote cell division. 
3. Promote fruit growth. 
4. Promote root initiation & flower initiation. 
5. Control geotropic behaviour. 
6. Stimulate respiration. 
7. Promote reproductive processes. 
8. Prevent leaf and fruit fall. 
 
2. Gibberellins 
1. Promote cell enlargement and cell division.  
2. Help in breaking dormancy in seeds and buds. 
3. Promote flowering. 
4. Increase cell size. 
5. Induce germination in dark. 
6. Counter act the effect of growth inhibitors. 
7. Promote growth in fruits. 
8. Prevent ageing of leaves.  
 
3. Cytokinins 
1. Promote cell division. 
2. Help in breaking the dormancy of seeds and buds. 
3. Delay the ageing of leaves. 
4. Promote the opening of stomata. 
5. Delay senescence (ageing). 
6. Provide resistance to plants against very high and low 
temperature from injuries. 
7. Provide nutrient transport. 
8. Enhances rate of synthesis of chlorophyll. 
 
4. Abscisic Acid (ABA) 
1. Inhibits growth and retards the developmental processes. 
2. Accelerates senescence. 
3. Promotes falling of leaves (abscission). 
4. Promotes stomata closure. 
5. It inhibits seed germination. 
6. It provides resistance against cold. 
7. Inhibits the synthesis of RNA and proteins. 
8. Promotes dormancy in seeds and buds. 
 
5. Ethylene (Ethane)  
1. Inhibits longitudinal growth. 
2. Inhibits the growth of roots and development of lateral 
buds. 
3. Promotes turning of leaves yellow and shedding of plant. 
4. Promotes ripening of fruit. 
5. Promotes flowering. 
6. Promotes breaking dormancy in several plant organs. 
7. Accelerates abscission of leaves, flowers and fruits. 
8. Someway lowers the auxin level in the tissue thus makes 
the stem ageotropic. 
 
Plant Movements 
The movement in any part of a plant is usually a growth 
movement. The movements in plant parts are caused by an 
unequal growth in roots and shoots by the action of 
hormones, under the influence of stimulus. 
 
Tropism 
The movement of a part of a plant in response to an external 
stimulus is called tropism. It is a directional movement of part 
of a plant caused by its growth. The growth of a plant part in 
response to a stimulus can be towards the stimulus (positive 
tropism) or away from the stimulus (negative tropism). 
 
Types Of Tropism 
1. Phototropism 
2. Geotropism 
3. Chemotropism 
4. Hydrotropism 
 
1. Phototropism 
The movement of a part of the plant in response to light is 
called phototropism. 
Example 
 
 
Stem or shoot of a plant bends towards the light is a positive 
phototropism. Roots of a plant moves away from light is called 
negative phototropism. The plant shoots respond to light and 
bend towards it due to action of auxin hormone. This happens 
as follows:- 
 
              
1.  When the sunlight falls from above, the auxin hormone 
present on the tip of the stem spreads uniformly down the 
stem. Due to the equal presence of auxin both the sides 
of the stem grows equally rapidly and grows straight. 
2. When the light falls on only one side of the stem then the 
auxin hormone collects on the opposite side (shady side) 
because auxin hormone prefers to stay in shade. 
3. Now more auxin hormone is present on one side but not 
on the other. Due to this one side of stem where auxin is 
present grows faster than the other side where there are 
no auxins. Since one side of the stem grows faster and 
becomes bigger than the other therefore the stem bends 
towards the other side (weaker side which lacks auxins). 
 
2. Geotropism 
The response of a plant to gravity is called geotropism  
 
Example 
The roots of a plant always grow down in response to gravity 
(positive geotropism). Shoots of a plant always grow up away 
from the pull of gravity (negative geotropism). This can be 
shown as follows:- 
 
1. When a potted plant growing in a transparent jar is kept 
in a normal position we can see its roots growing down 
wards and stem growing upwards. 
2.  Now if pot is tilted and kept in horizontal direction the 
roots and stem both are parallel to the ground. After a 
few days we will find that roots of this potted plant bend 
downwards and shoot upwards showing the effect of 
geotropism. 
 
3. Chemotropism 
The growth or movement of the part of a plant due to a 
chemical stimulus is called chemotropism.   
Example 
The growth or movement of a pollen tube towards the ovule is 
induced by stimulus of a sugary substance. The stigma of the 
carpel of a flower secretes a chemical (sugary substance) into 
the style towards the ovary.  The sugary substance acts as a 
stimulus for the pollen grains which fall on the stigma of the 
carpel. The pollen grains respond to this stimulus by growing a 
pollen tube in the downward direction into the style of the 
carpel and reaches to the ovule in the ovary. 
 
4. Hydrotropism 
The response of a plant towards the stimulus of water is called 
hydrotropism. 
Example 
The roots of the plant always show positive hydrotropism 
whereas the shoot of the plant always show negative 
hydrotropism. 
 
Nastic Movements 
The movement of a plant part in response to a stimulus which 
takes place in any direction neither towards the stimulus nor 
away from the stimulus is called nastic movement. The nastic 
movements of plants are induced by stimuli such as heat, 
light, touch (or contact) etc. The direction of nastic movement 
is not determined by the direction from which the stimulus is 
applied. Nastic movements are mostly exhibited by flat organs 
of the plants like leaves and petals of a flower. 
 
 
 
 
Example 
Mimosa plant (touch-me-not) shows nastic movement. If we 
touch the leaves of a mimosa plant with our finger then all its 
leaves fold up and droop. A number of flowers mainly of the 
daisy family, close up when light fades in the evening and re-
open the next day when light appears. This is an example of 
nastic movement. The stimulus in this case is light. 
 
Coordination in Animals 
The multicellular animals (except sponges) have specialized 
cells called nerve cells to respond to stimuli and coordinate 
their activities. 
 
Nervous System 
Nervous system is a system of neurons/nerve cells, nerves and 
nervous organs that coordinate and control the activities of 
different parts of an animal body by receiving and sending 
nerve impulses. 
 
Functions Of Nervous System 
1. Making the animal aware of the environment. 
2. Receiving information about the changes in the 
environment, processing and responding them. 
3. Memory of past experiences and expressions. 
4. Interpretation of external changes with the help of 
memory. 
5. Producing sensation like pain, pleasure, smell, taste, 
vision, hearing etc. with the help of special sense organs. 
6. Linking different body parts and coordinating their 
functions. 
7. Controlling activities of muscles and glands.  
8. Knowing changes or disturbances in the interior of the 
body.  
9. Taking immediate remedial action for harmful sensations 
without consulting will of animals.  
10. It is control system for all our actions, thinking & 
behaviour.  
11. Coordinate involuntary processes of our body like heart 
beat and breathing etc.  
12. It acts like a manager inside animal’s body. 
 
Control And Coordination In Higher Animals 
The complete control and coordination in higher animals 
occurs due to the combined action of both nervous system and 
endocrine system (hormonal system) together called 
neuroendocrine system. 
 
Receptor 
 A receptor is a cell or a group of cells which are sensitive to a 
particular type of stimulus. There are certain types of 
receptors like:- 
Thermo receptors  :  For heat 
Photoreceptors  :  For light 
Phonoreceptors   :  For sound 
Olfactory receptors  :  For smell 
The receptors are a kind of sense organs. The receptors 
collect the information from around the animal and send it to 
brain or spinal cord through sensory neurons. Motor neurons 
then transmit the response from brain or spinal cord to the 
effector organs. 
 
Effector 
The part of body which responds to the stimulus is called 
effector.  Effectors are mainly the muscles and glands. 
 
Control And Coordination In Humans 
In human beings the complete control and coordination occurs 
due to the combined action of two systems: - 
1. Nervous System 
2. Endocrine System 
That is why it is called neuroendocrine system. 
 
Human Nervous System 
 
The Fundamental Unit Of Nervous System – Neuron 
A neuron is the structural and functional unit of nervous 
system. Nervous system is thus made up of special cells called 
neurons. Neuron is the largest cell in the body. The neurons 
carry messages in the form of electrical signals called nerve 
impulses over large distances in the body quickly. 
 
Components Of Neuron   
1. Cell Body 
2. Dendrites 
3. Axon 
 
Cell Body 
It is like a typical animal cell which contains cytoplasm and a 
nucleus. A number of long and thin nerve fibers stretch out 
from the cell body of a neuron. 
 
Dendrites 
The shorter fibers on the body of a neuron are called 
dendrites. The dendrites pick up the nerve impulses from near 
by neurons and pass to cell body. 
 
Axon 
The longest fibre on a cell body of a neuron is called axon. 
The axon has an insulating and protective sheath (or cover) of 
myelin (made up of fats and proteins) around it. The axon 
 
 
passes the impulses from cell body to another neuron through 
a junction called synapse. 
 
Synapse 
A microscopic gap between a pair of adjacent neurons over 
which nerve impulses pass when going from one neuron to the 
next is called a synapse. Thus synapses connect neurons. 
Synapse act like one way valve. This is because the 
transmitter substance is present on only one side of the gap. 
Due to this nerve impulses through a particular set of neurons 
can go across anywhere only from one side. The electrical 
impulse travels from dendrite to the cell body and then along 
the axis to its end. At the end the electric impulse sets off the 
release of some chemicals. These chemicals cross the synapse 
and start the similar electric impulse in the dendrite of another 
neuron. This is how signals get transferred. 
 
 
Types Of Neurons 
There are three types of neurons. 
1. Sensory Neurons (Afferent Neurons)  
Sensory neurons transmit impulses from the sensory cells (or 
receptors) towards the central nervous system (spinal cord 
and brain). 
2. Motor Neurons (Efferent Neurons) 
Motor Neurons transmit impulses from the central nervous 
system (spinal cord and brain) towards the muscle cells (or 
effectors). 
3. Relay Neurons (Connective Neurons) 
Relay neurons occur in the central nervous system where they 
serve as links between sensory and motor neurons. 
 
Nerve Fibre 
An axon of a neuron covered by one or two sheaths is called 
nerve fibres. The nerve fibres may be microscopic or upto one 
metre in length. 
 
Nerves 
Bundles of nerve fibres covered by connective tissue sheath 
constitute nerves. The nerves arise from the brain and spinal 
cord to innervate various body parts. 
 
 
 
 
Central Nervous System (CNS) 
The central nervous system consists of brain and the spinal 
cord. The work of central nervous system is to direct incoming 
messages to the motor neurons that are connected to the part 
of the body which will respond to a stimulus. 
 
The Brain  
The brain is placed well protected in the cranial (cranium) 
cavity or brain box of skull. The brain is surrounded by three 
membranes called meninges. Between the meninges spaces 
are present which are filled with cerebro spinal fluid (CSF) 
which protects brain from mechanical shocks. 
 
Structure Of Brain 
Human brain is whitish bilaterally symmetrical structure that 
weighs about 1200-1400 gram and forms about 8% of the 
Cerebro Spinal Fluid (CNS). Brain is broadly divided into three 
regions: - 
1. Forebrain or Prosencephalon 
2. Mid brain or Mesencephalon 
3. Hindbrain or Rhombencephalon 
 
 
Forebrain Or Prosencephalon 
It is the largest part of the human brain that forms about 4/5
th
 
of the brain. It is divided into:- 
1. Cerebrum     2. Olfactory lobes 
 
Nervous 
System 
CNS PNS 
Brain Spinal 
Cord 
Fore 
Brain 
Mid 
Brain 
Hind  
Brain 
Olfactory 
Lobes 
Cerebrum Cerebellu-
m 
Frontal 
Lobe 
Parietal 
Lobe 
Occipital 
Lobe 
Temporal 
Lobe 
Medulla 
Oblongata 
Pons 
 
Page 5


 
 
CONTROL AND COORDINATION
Control 
The word control means to keep a check on the working of the 
organs in case of living organisms. It also means to make the 
organs work according to the requirement. 
 
Coordination 
The working together of the various organs of an organism in 
a systematic manner so as to produce a proper reaction to the 
stimulus is called coordination. 
 
Stimulus  
The change in the environment to which the organisms 
respond and react is called stimulus (plural stimuli). The 
reaction to the stimulus is a characteristic property of living 
organisms. Examples of stimuli are light, heat, cold sound, 
smell, taste, touch, pressure, water and force of gravity etc. 
The response of an organism to a stimulus is generally in the 
form of some movement of the body part. The animals can 
react to stimuli in many different ways. The plants react to 
stimuli in a very limited way. 
 
Control And Coordination In Plants 
Control and Coordination is done in plants by only one system 
i.e., Hormonal System. The hormones working inside plants 
are called phytohormones. The plants coordinate their 
behaviours against environmental changes by using hormones. 
The plants respond to various stimuli very slowly by growing. 
It usually takes a considerable time to observe the affect of 
stimulus on a plant. Plants can sense the presence of stimuli 
like light, gravity, chemicals, water etc. and respond to them. 
 
Plant Hormones (Phytohormones) 
There are five major types of plants hormones: - 
1. Auxins 
2. Gibberellins 
3. Cytokinins 
4. Absicic Acid (ABA)   
5. Ethylene (or Ethene) 
 
1. Auxins 
1. Promote cell enlargement and cell differentiation. 
2. Promote cell division. 
3. Promote fruit growth. 
4. Promote root initiation & flower initiation. 
5. Control geotropic behaviour. 
6. Stimulate respiration. 
7. Promote reproductive processes. 
8. Prevent leaf and fruit fall. 
 
2. Gibberellins 
1. Promote cell enlargement and cell division.  
2. Help in breaking dormancy in seeds and buds. 
3. Promote flowering. 
4. Increase cell size. 
5. Induce germination in dark. 
6. Counter act the effect of growth inhibitors. 
7. Promote growth in fruits. 
8. Prevent ageing of leaves.  
 
3. Cytokinins 
1. Promote cell division. 
2. Help in breaking the dormancy of seeds and buds. 
3. Delay the ageing of leaves. 
4. Promote the opening of stomata. 
5. Delay senescence (ageing). 
6. Provide resistance to plants against very high and low 
temperature from injuries. 
7. Provide nutrient transport. 
8. Enhances rate of synthesis of chlorophyll. 
 
4. Abscisic Acid (ABA) 
1. Inhibits growth and retards the developmental processes. 
2. Accelerates senescence. 
3. Promotes falling of leaves (abscission). 
4. Promotes stomata closure. 
5. It inhibits seed germination. 
6. It provides resistance against cold. 
7. Inhibits the synthesis of RNA and proteins. 
8. Promotes dormancy in seeds and buds. 
 
5. Ethylene (Ethane)  
1. Inhibits longitudinal growth. 
2. Inhibits the growth of roots and development of lateral 
buds. 
3. Promotes turning of leaves yellow and shedding of plant. 
4. Promotes ripening of fruit. 
5. Promotes flowering. 
6. Promotes breaking dormancy in several plant organs. 
7. Accelerates abscission of leaves, flowers and fruits. 
8. Someway lowers the auxin level in the tissue thus makes 
the stem ageotropic. 
 
Plant Movements 
The movement in any part of a plant is usually a growth 
movement. The movements in plant parts are caused by an 
unequal growth in roots and shoots by the action of 
hormones, under the influence of stimulus. 
 
Tropism 
The movement of a part of a plant in response to an external 
stimulus is called tropism. It is a directional movement of part 
of a plant caused by its growth. The growth of a plant part in 
response to a stimulus can be towards the stimulus (positive 
tropism) or away from the stimulus (negative tropism). 
 
Types Of Tropism 
1. Phototropism 
2. Geotropism 
3. Chemotropism 
4. Hydrotropism 
 
1. Phototropism 
The movement of a part of the plant in response to light is 
called phototropism. 
Example 
 
 
Stem or shoot of a plant bends towards the light is a positive 
phototropism. Roots of a plant moves away from light is called 
negative phototropism. The plant shoots respond to light and 
bend towards it due to action of auxin hormone. This happens 
as follows:- 
 
              
1.  When the sunlight falls from above, the auxin hormone 
present on the tip of the stem spreads uniformly down the 
stem. Due to the equal presence of auxin both the sides 
of the stem grows equally rapidly and grows straight. 
2. When the light falls on only one side of the stem then the 
auxin hormone collects on the opposite side (shady side) 
because auxin hormone prefers to stay in shade. 
3. Now more auxin hormone is present on one side but not 
on the other. Due to this one side of stem where auxin is 
present grows faster than the other side where there are 
no auxins. Since one side of the stem grows faster and 
becomes bigger than the other therefore the stem bends 
towards the other side (weaker side which lacks auxins). 
 
2. Geotropism 
The response of a plant to gravity is called geotropism  
 
Example 
The roots of a plant always grow down in response to gravity 
(positive geotropism). Shoots of a plant always grow up away 
from the pull of gravity (negative geotropism). This can be 
shown as follows:- 
 
1. When a potted plant growing in a transparent jar is kept 
in a normal position we can see its roots growing down 
wards and stem growing upwards. 
2.  Now if pot is tilted and kept in horizontal direction the 
roots and stem both are parallel to the ground. After a 
few days we will find that roots of this potted plant bend 
downwards and shoot upwards showing the effect of 
geotropism. 
 
3. Chemotropism 
The growth or movement of the part of a plant due to a 
chemical stimulus is called chemotropism.   
Example 
The growth or movement of a pollen tube towards the ovule is 
induced by stimulus of a sugary substance. The stigma of the 
carpel of a flower secretes a chemical (sugary substance) into 
the style towards the ovary.  The sugary substance acts as a 
stimulus for the pollen grains which fall on the stigma of the 
carpel. The pollen grains respond to this stimulus by growing a 
pollen tube in the downward direction into the style of the 
carpel and reaches to the ovule in the ovary. 
 
4. Hydrotropism 
The response of a plant towards the stimulus of water is called 
hydrotropism. 
Example 
The roots of the plant always show positive hydrotropism 
whereas the shoot of the plant always show negative 
hydrotropism. 
 
Nastic Movements 
The movement of a plant part in response to a stimulus which 
takes place in any direction neither towards the stimulus nor 
away from the stimulus is called nastic movement. The nastic 
movements of plants are induced by stimuli such as heat, 
light, touch (or contact) etc. The direction of nastic movement 
is not determined by the direction from which the stimulus is 
applied. Nastic movements are mostly exhibited by flat organs 
of the plants like leaves and petals of a flower. 
 
 
 
 
Example 
Mimosa plant (touch-me-not) shows nastic movement. If we 
touch the leaves of a mimosa plant with our finger then all its 
leaves fold up and droop. A number of flowers mainly of the 
daisy family, close up when light fades in the evening and re-
open the next day when light appears. This is an example of 
nastic movement. The stimulus in this case is light. 
 
Coordination in Animals 
The multicellular animals (except sponges) have specialized 
cells called nerve cells to respond to stimuli and coordinate 
their activities. 
 
Nervous System 
Nervous system is a system of neurons/nerve cells, nerves and 
nervous organs that coordinate and control the activities of 
different parts of an animal body by receiving and sending 
nerve impulses. 
 
Functions Of Nervous System 
1. Making the animal aware of the environment. 
2. Receiving information about the changes in the 
environment, processing and responding them. 
3. Memory of past experiences and expressions. 
4. Interpretation of external changes with the help of 
memory. 
5. Producing sensation like pain, pleasure, smell, taste, 
vision, hearing etc. with the help of special sense organs. 
6. Linking different body parts and coordinating their 
functions. 
7. Controlling activities of muscles and glands.  
8. Knowing changes or disturbances in the interior of the 
body.  
9. Taking immediate remedial action for harmful sensations 
without consulting will of animals.  
10. It is control system for all our actions, thinking & 
behaviour.  
11. Coordinate involuntary processes of our body like heart 
beat and breathing etc.  
12. It acts like a manager inside animal’s body. 
 
Control And Coordination In Higher Animals 
The complete control and coordination in higher animals 
occurs due to the combined action of both nervous system and 
endocrine system (hormonal system) together called 
neuroendocrine system. 
 
Receptor 
 A receptor is a cell or a group of cells which are sensitive to a 
particular type of stimulus. There are certain types of 
receptors like:- 
Thermo receptors  :  For heat 
Photoreceptors  :  For light 
Phonoreceptors   :  For sound 
Olfactory receptors  :  For smell 
The receptors are a kind of sense organs. The receptors 
collect the information from around the animal and send it to 
brain or spinal cord through sensory neurons. Motor neurons 
then transmit the response from brain or spinal cord to the 
effector organs. 
 
Effector 
The part of body which responds to the stimulus is called 
effector.  Effectors are mainly the muscles and glands. 
 
Control And Coordination In Humans 
In human beings the complete control and coordination occurs 
due to the combined action of two systems: - 
1. Nervous System 
2. Endocrine System 
That is why it is called neuroendocrine system. 
 
Human Nervous System 
 
The Fundamental Unit Of Nervous System – Neuron 
A neuron is the structural and functional unit of nervous 
system. Nervous system is thus made up of special cells called 
neurons. Neuron is the largest cell in the body. The neurons 
carry messages in the form of electrical signals called nerve 
impulses over large distances in the body quickly. 
 
Components Of Neuron   
1. Cell Body 
2. Dendrites 
3. Axon 
 
Cell Body 
It is like a typical animal cell which contains cytoplasm and a 
nucleus. A number of long and thin nerve fibers stretch out 
from the cell body of a neuron. 
 
Dendrites 
The shorter fibers on the body of a neuron are called 
dendrites. The dendrites pick up the nerve impulses from near 
by neurons and pass to cell body. 
 
Axon 
The longest fibre on a cell body of a neuron is called axon. 
The axon has an insulating and protective sheath (or cover) of 
myelin (made up of fats and proteins) around it. The axon 
 
 
passes the impulses from cell body to another neuron through 
a junction called synapse. 
 
Synapse 
A microscopic gap between a pair of adjacent neurons over 
which nerve impulses pass when going from one neuron to the 
next is called a synapse. Thus synapses connect neurons. 
Synapse act like one way valve. This is because the 
transmitter substance is present on only one side of the gap. 
Due to this nerve impulses through a particular set of neurons 
can go across anywhere only from one side. The electrical 
impulse travels from dendrite to the cell body and then along 
the axis to its end. At the end the electric impulse sets off the 
release of some chemicals. These chemicals cross the synapse 
and start the similar electric impulse in the dendrite of another 
neuron. This is how signals get transferred. 
 
 
Types Of Neurons 
There are three types of neurons. 
1. Sensory Neurons (Afferent Neurons)  
Sensory neurons transmit impulses from the sensory cells (or 
receptors) towards the central nervous system (spinal cord 
and brain). 
2. Motor Neurons (Efferent Neurons) 
Motor Neurons transmit impulses from the central nervous 
system (spinal cord and brain) towards the muscle cells (or 
effectors). 
3. Relay Neurons (Connective Neurons) 
Relay neurons occur in the central nervous system where they 
serve as links between sensory and motor neurons. 
 
Nerve Fibre 
An axon of a neuron covered by one or two sheaths is called 
nerve fibres. The nerve fibres may be microscopic or upto one 
metre in length. 
 
Nerves 
Bundles of nerve fibres covered by connective tissue sheath 
constitute nerves. The nerves arise from the brain and spinal 
cord to innervate various body parts. 
 
 
 
 
Central Nervous System (CNS) 
The central nervous system consists of brain and the spinal 
cord. The work of central nervous system is to direct incoming 
messages to the motor neurons that are connected to the part 
of the body which will respond to a stimulus. 
 
The Brain  
The brain is placed well protected in the cranial (cranium) 
cavity or brain box of skull. The brain is surrounded by three 
membranes called meninges. Between the meninges spaces 
are present which are filled with cerebro spinal fluid (CSF) 
which protects brain from mechanical shocks. 
 
Structure Of Brain 
Human brain is whitish bilaterally symmetrical structure that 
weighs about 1200-1400 gram and forms about 8% of the 
Cerebro Spinal Fluid (CNS). Brain is broadly divided into three 
regions: - 
1. Forebrain or Prosencephalon 
2. Mid brain or Mesencephalon 
3. Hindbrain or Rhombencephalon 
 
 
Forebrain Or Prosencephalon 
It is the largest part of the human brain that forms about 4/5
th
 
of the brain. It is divided into:- 
1. Cerebrum     2. Olfactory lobes 
 
Nervous 
System 
CNS PNS 
Brain Spinal 
Cord 
Fore 
Brain 
Mid 
Brain 
Hind  
Brain 
Olfactory 
Lobes 
Cerebrum Cerebellu-
m 
Frontal 
Lobe 
Parietal 
Lobe 
Occipital 
Lobe 
Temporal 
Lobe 
Medulla 
Oblongata 
Pons 
 
 
Cerebrum (Largest Part) 
Cerebrum is the dome shaped roof of the brain. It is made up 
of two hemispheres called cerebral hemispheres. They cover 
all parts of the brain. The two cerebral hemispheres are 
separated from each other by a very deep groove called 
cerebral fissure. There are specific regions in cerebrum for 
each kind of stimulus and its response. The cerebral 
hemispheres are divided into four lobes:- 
 
1. Frontal lobe 
 It is the region for speech, facial muscular activities and 
 higher mental activities. 
2. Parietal lobe 
 It is the region for taste, smell, touch, temperature and 
 conscious association. 
3. Occipital Lobe 
 It is the region for sight (visual reception) 
4. Temporal Lobe 
 It is the region for hearing (auditory reception) 
 
A separate part of the forebrain is associated with hunger 
which gives us the sensation of feeling full when we have 
eaten sufficiently. 
 
     
Olfactory lobes 
The olfactory lobes of brain of human beings are a pair of 
poorly developed club shaped widely separated bodies which 
are visible from the ventral surface only. The olfactory lobes 
are concerned with sense of smell. It contains olfactory 
receptors. 
 
Midbrain Or Mesencephalon 
Midbrain is small thick stalk, about 2 cm long. It connects 
forebrain with hindbrain. 
 
Function 
(i) Midbrain controls sight and auditory impulses. 
(ii) It controls reflex movements of the head, neck and trunk 
 in response to visual and auditory stimuli. 
(iii) It also controls reflex movements of the eye muscles, 
 change in pupil size and shape of eye lens. 
 
Hindbrain Or Rhombencephalon 
It is the posterior, small part of the brain. It consists of: - 
1. Pons verolii 2. Cerebellum 3. Medulla Oblongata 
 
1. Pons Verolii 
It is a thick, white, rounded ridge dorsally covered by 
cerebellum. 
 
Functions 
(i) It carries impulses from medulla oblongata to fore brain 
 and form one lobe of the cerebellum to other lobe. 
(ii) It also takes part in regulating respiration. 
 
2. Medulla Oblongata 
It is about 2.5 cm long that extends from pons to spinal cord. 
It is almost triangular in shape. It is hollow from inside 
containing a cavity. 
 
Functions 
(i) Cardiac activities are controlled by medulla oblongata. 
(ii) It controls breathing, blood pressure, regulate swallowing, 
coughing, sneezing and vomiting. 
 
3. Cerebellum 
It is the largest part of hind brain present below the cerebrum 
and above medulla oblongata, behind the pons. It certain two 
large lateral lobes could cerebella hemispheres. The 
cerebellum is solid from inside. 
 
Functions 
(i) It helps to maintain a balance or equilibrium during 
movements. 
(ii) It coordinates the body movements and posture. 
(iii) It controls and coordinates movements of various groups 
of muscles. 
 
Spinal Cord 
Spinal cord is the other part of the central nervous system 
which helps in the control and coordination of the body apart 
from brain. It is a 40-45 cm long cylindrical structure made up 
of nervous tissue. It is present at the back of the body and is 
well protected under the bony cage of vertebral coloumn. Like 
brain it is also surrounded by a layer of three membranes 
called meninges which are filled with a fluid called cerebro -
spinal fluid. 31 pairs of nerves arise from the spinal cord which 
connects all the body parts. 
                
Function 
Spinal cord controls the reflex actions of the whole body other 
than head and neck. It is because nerves from all over the 
body meet in a bundle in the spinal cord on their way to brain.