NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

1. Which of the following is a plant hormone?

(a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin.

Answer: (d) Cytokinin

2. The gap between two neurons is called a

(a) dendrite. (b) synapse. (c) axon. (d) impulse.

Answer: (b) synapse

3. The brain is responsible for

(a) thinking. (b) regulating the heartbeat. (c) balancing the body. (d) all of the above.

Answer: (d) all of the above.

4. What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Answer: Receptors are the sensory cells present all over the body. For eye and ear, receptors are grouped. In case of skin, receptors are scattered. Following are the functions of receptors –

• Sensation of external stimuli i.e. sense of heat or sense of pain
• Trigger impulse in sensory neuron that sends message to spinal cord

If receptors are damaged then external stimuli will not be felt by the body. For an example, person accidentally touches a hot pan, there will be no sense of the external stimuli, thus, hand will get burn.

5. Draw the structure of a neuron and explain its function.

Answer:

Function of neuron:

• Axon conducts messages away from the cell body
• Dendrites receives information from other cell and pass messages to cell body
• Cell body is responsible for growth and maintenance of the cell.

6. How does phototropism occur in plants?

Answer: Phototropism is growth and movement of plant in the direction of light. It occurs due to increased auxin on dark side and decreased auxin on brighter side, due to which, leaf on the darker side grows faster, thereby moving towards the light source.

7. Which signals will get disrupted in case of a spinal cord injury?

Answer: All the nerves in the body meet in a bundle at spinal cord. If spinal cord is injured, then transmission of all nerve signals will be affected. This will affect transmission of impulses from receptors to brain and response from brain to the receptors.

8. How does chemical coordination occur in plants?

Answer: To stimulus, plants responds by showing movements. Growth, development, response to environment is controlled and coordinated by chemicals called hormones. These hormones are produced in one part of the body and later transferred to other parts of the body as per their needs. Some plant hormones are auxins, gibberellins, cytokinins, abscisic acid and ethylene. They are either growth promoters or growth inhibitors.

9. What is the need for a system of control and coordination in an organism?

Answer: Coordination is necessary for all activities we perform in our day to day life. Nervous system receives information from surrounding and it provides proper response to the received information. Endocrine glands secretes various hormones helpful for growth and development, reproduction and various reflex actions. In plants, photosynthesis, transpiration, growth and development are carried out with the help of hormones. Thus coordination is important for an organism.

10. How are involuntary actions and reflex actions different from each other?

Answer:

Involuntary Actions	Reflex Actions
Occurs without the consciousness of organism	Automatic response to the stimulus without involvement of brain
Occurs slowly	Very quick to that instant
Does not depend on external condition	Depends on external conditions
E.g. pumping of blood by heart	E.g. hand touched to hot objects is returned back.

11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Answer:

Nervous system	Hormonal system
Information is passed by electric impulses	Information is passed by chemical messengers
In coordination axon and dendrites pass information	Information is passed through blood
Information is passed quickly	Information is passed slowly
Effects are for short time	Effect are for long time
Cannot cause growth	Some hormones in hormonal system can cause growth

12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Answer:

Movement in sensitive plants	Movement in our legs
Movement in touch me not plant (mimosa) occurs in response to stimulus.	Movement of legs are voluntary action of human body
For such movement, electric signals are passed from cell to cell. Plants do not have such special tissues for conduction of electric signals.	Signals from these actions are passed to brain and thus can be controlled consciously.

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