CBSE Class 10 Science Important Questions Chapter 7 Control and Coordination Part 3

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3 Marks Questions

1. Mention three important functions of gibberellins.

Ans. Functions of Gibberllins –

(i) Stimulate stem elongation.

(ii) Help in breaking seed dormancy.

(iii) Promote flowering in some plants even under unfavourable conditions

(iv) Help in seed germination.

(v) Promote production of male flowers.

2. What is the function of receptors in our body? What happens when receptors do not work properly?

Ans. The function of receptors is to defect information form the environment. If receptors do not work properly, the information obtained from the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental stimulus will be delayed causing harm to the body.

3. What happens at the synapse between two neurons?

Ans. The nerve impulse gets transmitted through the synapse by means of chemical signals. When a stimulus acts on the receptor, chemical reaction is set off which produces an impulse in it. This impulse travels form the dendrite of presynaptic neuron to its cell body and then along its axon. At the end of axon of this neuron, the electrical impulse releases tiny amount of a chemical substance crosses the synapse and starts a similar electrical impulse in the dendrite of the next neuron.

4. What is the need for a system of control and co – ordination in an organism?

Ans. a) It evokes an appropriate movement in response to any change in external environment

b) Multicellular organisms have complex body. So it, co – ordinates various organs of body of an organism work together in a proper manner to produce proper reaction to stimulus

5. Pituitary is a master endocrine gland. Justify this statement.

Ans. Pituitary gland is also known as master gland because it controls the activities of most of the gland.

It regulates the secretion of other glands. Like

a) Growth hormones – Body growth and development of bones

b) Thyroid stimulating hormone – Secretion of hormones form thyroid gland.

c) Adrenocorticotropic hormone – Secretion of hormones form adrenal glands.

d) Follicle stimulating hormone – Stimulating of growth of ovaries and testes

e) Luteinsing hormone – Secretion of hormone from ovaries & testes f) prolactin – Regulation of function of mammary gland. Hence, most of functions are controlled by pituitary gland so it is called master gland.

6. Draw the structure of neuron and explain its function.

Ans. Neuron has three components –

(i) Cell body

(ii) Dendrites

(iii) Axon

Neuron has three components

Neuron Has Three Components

The dendrite picks up the nerve impulse from receptors and then pass the impulses to the cell body and then along the axon. The axon passes the impulse to another neuron through a junction called synapse.

7. How does our body respond when adrenaline is secreted into the blood?

Ans. When adrenaline is secreted into the blood, it prepares our body for action. It speeds up heart beat and breathing, raises blood pressure and allows more glucose to go into the blood to give us a lot of energy quickly to fight or urn away from frightening situation. The blood supply decreases form the skin and digestive system and increase to skeletal muscles. All there conditions help the individual to respond the emergency situation.

8. Where are Pons and medulla oblongata located? Write their functions.

Ans. Pons and medulla Oblongata are located in hind brain. Pons acts as bridge between brain and spinal cord. Medulla oblongata –

a) It is the reflex centre to control activities like salivation, swallowing, vomiting, breathing, coughing, sneezing and heart beat b) It also controls sleeps, consciousness and activities of cerebrum

9. List the function of testosterone and estrogen. Where are they secreted?

Ans. Testosterone is secreted in males – It is responsible for development of male sex organs and secondary sex characteristics like moustache, beard & voice.

Estrogen is secreted in females – it is responsible for development of female sex organs and secondary sex characteristics like mammary gland and uterine growth.

10. Define ‘nerve impulse’. Which structure in a neuron helps to conduct a nerve impulse?

a) Towards the cell body?

b) Away from the cell body?

Ans. Nerve Impulse – It is the passing of information through neurons is in the form of electrical and chemical signals. This is called nerve impulse.

a) Dendrite

b) Axon

11. Differentiate between axon and dendrons?

Ans.

Axon and Dendrons
Axon and dendrons

Axon

Dendron

They are long in size and one in number

They are small in size and numbers.

Generally unbranched

Branched

Terminal branches have swollen knobs

Terminal swollen knobs are absent.

Direction of nerve impulse is away from cyton

Direction of impulse is towards cyton.

12. Mention the structure of human brain.

Ans.

Human brain

Human Brain

13. What are tropic movements? Name the types of tropic movements in plants.

Ans. The bending or movement of a part of plant in response to the external stimulus is called tropism or tropical movement. It is of following types.

a) Phototropism – It is response to light. It may be towards light (positive) or away from the light (negative).

(b) Geotropism – It is response to gravity – It may be towards stimulus (positive) and away from the stimulus (negative)

(c) Chemotropism - Response to chemicals. It may be positive or negative.

(d) Hydrotropism – Response to water. It may be positive or negative.

14. Name the different lobes of cerebrum.

Ans. Different lobes of cerebrum –

a) Frontal lobe – It is associated with reasoning.

b) Parietal – Perception of general sensation s like pressure, touch and pain.

c) Occipital – Visual perception.

d) Temporal – Important for interpreting sounds and the language we hear and formation of memories.

15. How do auxins promote the growth of tendril around a support?

Ans. When the tip of a tendril touches a support, then the auxins present in its tip move to that side of tip which is away form the support, auxins promote growth. So, due to more auxins in it, the side of tendril, away from the support, grow faster and becomes longer than the side which is in contact with the support and makes the tendril curve towards the support.

16. Write different between exocrine and endocrine glands.

Ans.

Exocrine and Endocrine Glands
Exocrine and endocrine glands

Exocrine gland

Endocrine gland

Glands with ducts.

Ductless glands

They secrete enzymes

They secrete the hormones

Pour their secretion in ducts of the gland.

Pour their secretion directly in to blood

Glands are located nearby the site of action

Glands are located away from the site of action

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