cls 10 chp 7 solsn

Class 10 Science Solution
     Chapter 7 Control and Coordination      

 Intext Question and Answer      

Page Number: 119        

1. What is the difference between a reflex action and walking?
Ans:

Reflex action	Walking
1. It is the action which is performed automatically.	1. It is a response to the information transmitted by nerve to muscles of the legs. In this case, thinking is involved.
2. It is controlled and coordinated by spinal cord.	2. Brain instructs and controls leg muscles to move.
3. It is an involuntary action.	3. It is a voluntary action.

2. What happens at the synapse between two neurons?

Ans:

The small empty space between two nerve cells is called synapse. At synapse, a chemical substance is produced at the end of axon of one nerve cell that reaches to the other nerve cell through the dendrite.

3. Which part of the brain maintains posture and equilibrium of the body ?
Ans:
Posture and equilibrium of the body are controlled by cerebellum.

4. How do we detect the smell of an agarbatti (incense stick) ?
Ans:

★ The smell of agarbatti (incense stick) diffuses in the air.

★ It is detected by olfactory receptors present in the nose.

★ This information is sent to olfactory lobe by sensory nerves located in the forebrain.

★ It responds to the information.

5. What is the role of the brain in reflex action ?

Ans:

There is no role of brain in reflex action. These involuntary actions are controlled by the spinal cord which take place immediately without thinking of how to respond to the stimuli.

Page Number: 122          

1. What are plant hormones ?
Ans:
Plant hormones are also called phytohormones. Plant hormones are the chemical substances which help in controlling growth, flowering, height, development of plants and their response to the environment.

2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light ?
Ans:

Movement of leaves of sensitive plant	Movement of a shoot towards light
1. It is a nastic movement which does not depend on the direction of stimulus applied.	1. It is a tropic movement which depends on the direction of stimulus applied.
2. The stimulus is touch.	2. The stimulus is light.
3. It is caused by the sudden loss of water from the swellings at the base of leaves.	3. It is caused by the unequal growth on the two sides of the shoot.
4. It is not a growth movement.	4. It is a growth movement.

3. Give an example of a plant hormone that promotes growth.                                

Ans:                                                                                                                               

Auxin.

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

Ans:                                                                                                                                  

When a tendril comes in contact with a support, auxin stimulates faster growth of the cells on the opposite side that's why the tendril forms a coil around the support.

5. Design an experiment to demonstrate hydrotropism.

Ans:

Take two glass troughs A and B and fill each one of them two-thirds with soil. In trough A plant a tiny seedling. In trough B plant a similar seedling and place a c/ay pot inside the soil. Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in the clay pot. Leave both the troughs for a few days.

Page number 125         

1. How does chemical coordination take place in animals?

Ans:

★ Chemical coordination takes place in animals with the help of chemical messengers called hormones. 

★ Hormones are the chemicals that are secreted by specific endocrine glands. Hormones regulate the growth, development and homeostasis of the animals.

 2. Why is the use of iodised salt advisable ?
Ans:
★ It is advised to use iodised salt because thyroid gland needs iodine to produce thyroxin hormone. 

★ Thyroxin hormone controls all the metabolic activities of our body like metabolism of carbohydrates, fats and protein etc. 

★ Due to the deficiency of thyroxin a disease called goitre is caused.

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

Ans: 

★ Adrenaline is directly secreted into the blood. The blood to the skin is reduced due to contraction of muscles around small arteries.

★The breathing rate increases because of the contractions of the diaphragm and the rib muscles. The heart beats faster, resulting in supply of more oxygen to the muscles.

4. Why are some patients of diabetes treated by giving injections of insulin?

Ans :

★ Insulin hormone regulates blood sugar levels.

★ To treat increased level of blood sugar, the diabetic patients are treated by giving injections of insulin.

Exercise Questions        

1. Which of the following is a plant hormone?
(a) Insulin            (b) Thyroxin
(c) Oestrogen       (d) Cytokinin
Ans:    (d) Cytokinin

2. The gap between two neurons is called a
(a) dendrite      (b) synapse
(c) axon            (d) impulse
Ans:  (b) Synapse

3. The brain is responsible for
(a) thinking
(b) regulating the heart beat
(c) balancing the body
(d) all of the above
Ans: (b) 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 ? 

Ans:

(i) Phonoreceptors are found in Ear. Their function is to hear and balance of the body.

(ii) Photoreceptors are found in Eyes. Their function is to see.

(iii) Olfactory receptors are found in Nose. Their function is smell detection.

(iv) Thermoreceptors found in Skin.- Its function is to feel the heat, cold or touch.

(v) Gustatory receptors found in Tongue - Its function is to detect Taste.

When receptors do not work properly, the environmental stimuli are not able to create nerve impulses and body does not respond.

5. Draw the structure of a neuron and explain its function.
Ans:
Nerve cell or neuron is the functional unit of nervous system. A nerve cell has three parts-
(i) cell body
(ii) dendrite
(iii) axon

Function : 

★ The function of nerve cells is to carry information in the form of electrical signals which are called nerve impulses. 

★ Cells receive stimulus to send it to spinal cord and brain and carry the message from brain to the target organ.

6. How does phototropism occur in plants ?
Ans:
★ Phototropism in plants occurs due to the hormone auxin. 

★ When light falls on one side of a plant, the secretion of auxin hormone is more in the part away from the light. 

★ Hence, auxin causes growth in length of the cells in shady part. So, the plant appears to bend towards light.

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

Ans:

★ All the involuntary actions will get disturbed.

★ Reflex actions will be disturbed because reflexes are located in the spinal cord. Therefore, the quick responses required to safe guard the body will not take place.

8. How does chemical coordination occur in plants ?

Ans:

Chemical coordination in plants takes place with the help of plant hormones. In most of the regions where division takes place (meristematic regions) stimuli cells secrete chemical compounds (hormone). These substances identify the information by stimulating the other nearby cells and communicating the information.

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

Ans:

An organism needs control and coordination system for the following functions :

★  To save the body of the organisms from the harmful changes in the environment.

★  To control the speed of voluntary and involuntary actions.

★  To have the capability to think and learn for responding to any stimuli.

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

Involuntary actions	Reflex actions
1. Those actions which occur immediately without any thinking are called involuntary actions.	1. Reflex action is an immediate response to an event which does not require any processing by brain.
2. Involuntary actions are controlled by mid and hind brain. Example: Breathing, beating of heart, etc.	2. Reflex actions are controlled by spinal cord. Example: Sneezing, coughing, etc.

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

Ans:

Nervous mechanism	Hormonal mechanism
It is a fast process.	It is a slow process.
Arteries and glands are affected.	It affects the target organ.
It transmits in electrochemical form.	It transmits in chemical form.
It does not control metabolism.	It controls metabolism.
Growth is not affected.	Growth is affected.

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

Movement in a sensitive (mimosa) plant	Movement in legs of a human
1. The leaves of a sensitive plant like mimosa are sensitive to touch.	1. Leg is in control of nerve muscles.
2. It is not controlled by any part of the plant.	2. It is controlled by brain and spinal cord.
3. In this, cells change their shape on changing the amount of water in them.	3. Amount of water has no effect on the movement of muscles.
changing the amount of water in them.	the movement of muscles.
4. The movement in a sensitive plant are nastic movement.	4. The movement in our leg is due to voluntary nervous system.

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