CBSE Class 10th Biology | Control and Coordination | Control and Coordination in Animals

Control and Coordination in Animals


Multicellular organisms have specialized organ system to coordinate their activities. Simple multicellular organism like Hydra consists of a network of nerve cells. Thus Hydra has only nervous system to coordinate its activities.

The control and coordination in higher animals (Human) takes place through combination of nervous system and hormonal system, i.e. neuro-endocrine system.


Nervous system of Hydra


Nervous System in Animals


Nerve cells are the fundamental unit of nervous system. They are the specialized cells responsible for carrying information across the body. A nervous system consist of millions of nerve cells communicating through neurotransmitters among themselves. It is the longest cell in the body.

Structure of Neuron


A neuron consist of two components

1. Cyton (Cell body): It is like a typical animal cell, which contains cytoplasm and nucleus. Small processes stretches out from the cell body called dendrons which may further branch into dendrites.

2. Axon: It is a cylindrical structure arising from cyton and branched at its terminal ends. It has an insulating and protective sheath of myelin (made of fat and protein) around it. It is also known as nerve fibre.

A Neuron (Nerve cell)


Receptor and Effector


    There are five sense organs in our body: eyes, ears, nose, tongue and skin. In a sense organ a receptor is present, which is a cell or group of cells sensitive to a particular type of stimulus (change in environment) such as light, heat, sound etc.

Types of receptors



Types of Stimulus 

Sense organ 


Photo receptors

Detects light 



Phono receptors 

Detects sound 



Olfactory receptors 

Detects smell 



Gustatory receptors 

Detects taste 



Thermo receptors 

Detects heat or cold



The part of a body which can respond to stimulus according to the instruction sent from the nervous system is called effector. Effectors are mainly muscles and glands.

If we touch something hot (or smell something tasty) we need to detect it and this is done by specialized tips of some nerve cells located in our sense organs. This information is then transmitted to central nervous system (brain and spinal cord) from where the response of the same is conveyed to the effector organs (muscles and glands). The whole process is done by a set of 3 neurons.

Types of Neuron


There are three types of neurons

  1. Sensory neuron: It transmits information from receptors (sense organs) towards central nervous system (brain and spinal cord).
  2. Motor neuron: It transmits information from central nervous system to effectors (muscles or glands).
  3. Inter or Relay neuron: It occurs in central nervous system and serves as link between other neurons.

Transmission of Nerve Impulse


The messages that are transmitted in the nervous system are in the form of electrical or chemical signals called nerve impulses. The nerve impulses are transmitted from one neuron to another in a nervous system. There is a microscopic gap between two neurons over which nerve impulses pass while going from one neuron to the next and it is called synapse. A chemical substance called neurotransmitter (e.g. Acetylcholine) helps in carrying nerve impulses over synapse.



Steps for transmission of nerve impulse

  • A chemical reaction followed by an electrical impulse sets off when a stimulus acts on a receptor.
  • This impulse is transmitted from the dendrite of a sensory neuron to the terminal endings of its axon.
  • At the synapse, the neurotransmitter is released which undergoes a chemical reaction resulting in initiation of a similar impulse in the next neuron.
  • This impulse is again transmitted to the terminal endings of the next neuron and the process continues till it reaches the relay neuron in spinal cord and brain.
  • From the brain and spinal cord arises a set of motor neurons which transmits electrical impulses in the similar way to the effectors like muscles and glands.

Action caused by Effectors due to Nervous Tissue


The nerve impulse received by the muscles cause action or movement (removing our hand away from a hot object). Muscles are made of muscle cells containing special proteins which change their arrangement when stimulated by electrical impulses. This causes the muscle to change shape and contract. When the muscles contract, they pull the bones and make it move.

The neuromuscular junction i.e., the area of contact between a nerve fibre and sarcolemma is similar to axon-dendron junction or synapse. When a nerve impulse reaches the end of a nerve fibre, a neurotransmitter is released and it creates a similar electrical disturbance in the muscle cell bringing about its contraction.

Neuromuscular Junction


To sum up, the transmission of nerve impulse and action by effectors can be shown as follows.



Human Nervous System


Human nervous system is one of the most highly developed nervous system among living organisms on this planet.

The human nervous system can be further divided.



(a) Central Nervous System


It occupies the central axis of the body and enables a person to give a suitable response to various situations.

It consists of the

  1. Brain
  2. Spinal Cord


(i)    Brain: The brain is located in a bony case (skull) called cranium or brain box. Inside the cranium, the brain is further surrounded by three membranes called meninges. The space between the membranes and brain is filled with cerebrospinal fluid (CSF). The cranium, meninges and cerebrospinal fluid protects the brain from mechanical shocks.

Human brain


The brain is broadly divided into three regions.

Fore Brain: It consists of

Olfactory lobes: A pair of bodies covered by cerebrum. It is not so developed in humans. It is concerned with olfaction (smell).

Cerebrum: It forms about two-third of the brain. Different areas of cerebrum perform different functions. Association areas control learning, reasoning, intelligence, personality, thinking, memory, etc. Sensory areas give us sensation by receiving information from eyes, ears, nose, tongue, skin. Motor areas give instructions to muscles for various voluntary actions.


It controls reflex movements of the head, neck, eye muscles, etc. in response to visual or auditory stimuli.

Hind brain: It is further sub divided

Pons: It takes part in regulating respiration.

Cerebellum: It helps in maintaining posture and balance. It also coordinates smooth body movements like walking, riding, etc.

Medulla Oblongata: It controls various involuntary actions such as heart beat, breathing, peristaltic movements, etc. Medulla also controls reflex actions like, swallowing, sneezing, vomiting, etc.

Different regions of brain showing different functions

(ii)    Spinal Cord: It is rod-like structure extending downwards in continuation with medulla. It is enclosed in a bony cage called vertebral column and is also surrounded by meninges.

It is concerned with reflex actions and conduction of nerve impulses to and from the brain.

Reflex Action and Reflex Arc

Reflex action: A reflex action may be defined as a spontaneous, automatic and mechanical response to a stimulus, acting on a specific receptor, without the will of an animal.

Blinking of eyes, moving our foot away when we step on something sharp, etc. are examples of reflex action. In reflex action we are not aware of the things which is going to happen to us. In reflex action, spinal cord is involved for quick response to specific stimulus. However for thinking process, the information also goes to the brain.

The involvement of brain in reflex action is to think about the dangerous situation and the possibility of reaction. Such reflex action which involves brain are called cerebral reflexes. For example, the contraction of pupil of our eye automatically in the presence of bright light.    


Reflex arc


Reflex arc: The path taken by nerve impulses in a reflex action is called reflex arc.

When we accidentally touch something hot, the heat is sensed by the receptors present in the skin. A nerve impulse is triggered for the same in the sensory neuron which transmits message to the spinal cord. In the spinal cord, impulse is passed to the connector neuron which in turn passes it to the motor neuron. The motor neuron transmits the instruction to a muscle of our arm. The arm muscles contracts and pulls other hand away from the hot object.

(b) Peripheral Nervous System

All the nerves arising from brain and spinal cord forms the peripheral nervous system. Nerves arising from the brain are called cranial nerves which are twelve pairs. There are 31 pairs of nerves arising from the spinal cord (spinal nerve). Cranial nerves are either sensory, motor, or mixed in nature. All the spinal nerves are mixed.

(c) Autonomic Nervous System

It comprises of a set of two (sympathetic and parasympathetic) network of nerves antagonistic to each other. These nerves are attached to the smooth muscles of internal organs and controls involuntary actions.

For example: Sympathetic nerves increase the rate of heart beat and parasympathetic decrease the rate of heart beat.


CBSE Class 10th Biology | Control and Coordination | Control and Coordination in Plants

Control and Coordination | Control and Coordination in Plants


Control and Coordination in Plants

Plants lack nervous system and sense organs as animals have them e.g. eye, ear, etc. Plants react to the environmental changes by using hormones called Phytohormones.

According to K.V. Thimann, phytohormone can be defined as “an organic substance produced naturally in plants controlling growth and other functions at a site remote from its place of production and active in minute amounts”.

Growth regulator is a broader term applied to all naturally occurring hormones along with those which are synthetic substances. All growth regulators are not phytohormones but all phytohormones are growth regulators.

Phytohormones (Plant Hormones)

In plants, the growth and development is controlled by various plant hormones i.e. phytohormones. The growth and development is coordinated and managed by one hormone by affecting or controlling the one or the other aspect of plant growth.

The growth of a plant is divided into following three stages :

  1. Cell division
  2. Cell enlargement
  3. Cell differentiation

The various aspects of plants which are controlled by plant hormones are as follows :

  1. Promotion of dormancy
  2. Breaking of dormancy
  3. Stomatal control
  4. Falling of leaves
  5. Fruit growth
  6. Ripening of fruits
  7. Ageing in plants



Hormone Function
1. Auxin ·    Promotes cell enlargement and cell differentiation.

·    Promotes fruit growth.

2. Gibberellins ·    Promotes cell enlargement and cell differentiation in presence of auxin.
3. Cytokinin ·    Promotes cell division i.e. cytokinesis.

·    Helps in breaking the dormancy of seeds and buds.

·    Promotes opening of stomata.

4. Abscisic Acid
(A growth inhibitor)
·    Promotes the dormancy in seeds and buds.

·    Promotes the closing of stomata.

·    Promotes the wilting and falling of leaves.

Plant Movement

Plant shows movement in its different parts, when it is subjected to any external stimuli such as light, force of gravity, water, etc.

Have you ever thought why a plant bends towards light when you put a potted plant in a dark room and allow light to enter in the room via window. Let us explore.

Recall the knowledge of phytohormones. Auxin is the hormone which shows cell enlargement and cell division. When a plant is subjected to the above mentioned condition, due to the direct sunlight on one side the auxin synthesis increases which enhances the growth of stem on the other side thereby bending the plant towards light, which we call “plant movement”.

Plant movement is broadly studied under following two heads.

  1. Tropism or Tropic movement
  2. Nasties or Nastic movement

Tropism or Tropic movements

Tropic movement is the directional movement of the part of plant in response to external stimuli. The direction of response is determined by the direction of stimulus. The direction of movement of plant can be towards the stimulus i.e. positive tropism or can be away from the stimulus. i.e. negative tropism.

(a) Types of Tropism: Depending upon the type of stimuli, different types of tropism are classified. There are five types of well recognized stimuli studied and tropisms are also studied in response to them. They are

  • Light
  • Chemicals
  • Water
  • Gravity
  • Touch

Similarly, the types of tropisms are

Phototropism In response to light
Chemotropism In response to chemical
Hydrotropism In response to water
Geotropism In response to gravity
Thigmotropism In response to touch

(i) Phototropism:

can be defined as “the movement of plant parts in response to light”. When the plant parts move towards the light it is called positive phototropism and if it moves away from light, it is called negative phototropism.

For example, stem / shoot shows movement towards the light, which means shoot shows positive phototropism. Root shows movement away from the light i.e. negative phototropism.

Control and Coordination in Plants Class 10

Phototropism in Plants

Experiment and explanation:

Let us discuss one experiment before discussing the role of hormones.

When a plant is grown in a dark room, with its window open (the only source of light to the plant) tends to move towards light coming through window. This is because of the positive phototropism shown by plant.

The principle hormone taking part in phototropism is “Auxin”. The flowchart explaining the mechanism of auxin action is as follows:

Mechanism of Auxin action

Control and Coordination in Plants Class 10

Control and Coordination in Plants Class 10

Control and Coordination in Plants Class 10

Mechanism of Auxin Action (Normal growth)

Control and Coordination in Plants Class 10

Mechanism of Auxin Action (in experimental condition)

In case of root: The effect of auxin on root is just opposite to that of shoot.

(ii) Chemotropism:

It can be defined as “the movement of plant parts in response to chemicals”. When the plant parts move towards the chemical it is called “positive chemotropism” and if it moves away from the chemical then it is called “negative chemotropism”.

For example, during the process of fertilization, the pollen tube grows towards the ovule, because stigma produces a chemical in response to which pollen tube grows towards ovule.

Control and Coordination in Plants Class 10

Pollen grains moving towards ovule (Chemotropism)

The growth of pollen tube towards ovule is one of the finest examples of chemotropism in plant kingdom. The process is as follows:

Control and Coordination in Plants Class 10

In the above discussed flowchart, the sugary secretion by stigma acts as chemical to which plants show tropic movement.

(iii) Hydrotropism:

It can be defined as “the movement of plant parts in response to water”. When the plant parts move towards water, it is called positive hydrotropism and when it moves away from water, it is called negative hydrotropism.

Have you ever pulled off a plant? You will notice that roots grow in all directions, this is because in response to water they grow towards it, i.e. “hydrotropism”.

Let us try to understand the process of hydrotropism by a simple experiment.

Control and Coordination in Plants Class 10

Experiment and explanation: Take two glass troughs and label them 1 and 2. Plant a tiny seedling in both of them. In trough 2 make a small “well” and fill it with water. Water trough ‘1’ uniformly but in case of trough ‘2’, put water in the well.

After few days dig the soil without disturbing the root. We will notice that in case of trough 2 the root bends towards water where as in trough 1 root grows straight uniformly.

(iv) Geotropism:

It can be defined as “the movement of plant parts in response to gravity”. When the plant parts move towards the direction of gravity then it is termed as “positive geotropism” and when it moves away from the gravity, then it is termed as “negative geotropism“.

Shoot shows negative geotropism and root shows positive geotropism.

Have you ever thought of why stem grows upward against the gravity and root grows against the gravity?

Experiment and explanation: Let us understand the phenomenon with the help of an experiment. Take two potted plant namely 1 and 2. Keep one of them say 1 in normal condition and put 2 in horizontal condition.

Control and Coordination in Plants Class 10

You will notice that after some days the plant in pot ‘2’ bends i.e. stem away from earth and root towards the earth.

(v)    Thigmotropism:

It can be defined as “the movement of plant parts in response to touch“.

Stem tendril showing Thigmotropism

Stem tendril showing Thigmotropism

Have you ever seen a vine yard? The grape vine climbs on the provided support. Do you know why?

Experiment and explanation: The grape vine has a weak stem, so it cannot stand erect. To stand erect it needs support to which tendril (an outgrowth on the stem) binds. The tendril grows as it touches the support. The side of the tendril which touches the support grows slowly as compared to the other side which is not in contact. This phenomenon in response to touch is called as “thigmotropism”.

Usefulness of Tropic Movement: Considering all the tropic phenomenon we can conclude that these phenomenon are necessary for the plant to survive. If tendril would not have responded to the support, vine yard would not have been possible. If roots would not have responded to water, plant would have died.

Nasties or Nastic Movement

Nastic movement can be defined as, “the movement of plant part in response to an external stimuli in which the direction of response is not determined by the direction of stimulus“. It is usually shown by flat structure of plant such as leaf.

One of the best studied example of nastic movement is “response of Mimosa pudica on touch“.

Nastic movement may or may not be growth movement. The opening of flower by the action of sun light is a growth phenomenon where as folding of leaf on touch as in case of Mimosa pudica is not a growth phenomenon.

(a) Types of nastic movement

(i)    Thigmonasty:

Thigmonasty is the nastic movement of a plant part in response to touch. For example – Mimosa pudica responds to touch by folding its leaves. The stimulus here is touch.


Photonasty (in sunflower)

Photonasty (in sunflower)

(ii)    Photonasty:

Photonasty is the movement of plant part in response to light. The stimulus here is light. In case of dandelion flower it opens in the morning with the rising sun and as the sun sets flower also closes. But in case of moon flower it opens with the setting of sun and closes with the rising of sun. You can also see movement in sunflower which responds to the movement of sun.


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