NCERT Solutions for Class 10 Science Chapter 6 Control and Coordination

Ans.

1. At the end of the axon, the electrical impulse sets off the release of some chemicals.
2. At the synapse, these chemicals cross the gap and start a similar electrical impulse in a  dendrite of the next neuron.

Q3. Which part of the brain maintains posture and equilibrium of the body?

Ans. The posture and equilibrium of the body are maintained by cerebellum of the brain.

Q4. How do we detect the smell of an agarbatti (incense stick)?

Ans.

• The sense of smell of an incense stick is received by the receptor cells (olfactory cells) of nose.
• The olfactory cells convert the stimulus into electric impulses and carry them to olfactory centre of the brain.
• The brain analyses and detects the smell.

Q5. What is the role of brain in reflex action ?

Ans.

• The reflex action in which spinal cord is involved, brain acts as the information collecting centre.
• But in some other reflexes such as salivation at the site or smell of food, closing of eyes in bright light the brain acts as the relay centre transferring impulse from sensory to motor neuron.

Q6. What are plant hormones ?

Ans. The substances or hormones that help to coordinate growth, development and response to environment in plants are called plant hormones or phytohormones.

Q7. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light ?

Ans.

Q8. Give an example of a plant hormone that promotes growth.

Ans. Auxins

Q9. How do auxins promote the growth of a tendril around a support ?

Ans.

1. The growth of tendril around the support is caused by the auxin.
2. The side of the tendril towards the support has less hormone than the free side.
3. So, free side grows more and the tendril coils around the support.

Do Check: NCERT Solutions for Class 10

Q10. Design an experiment to demonstrate hydrotropism.

Ans. Aim : To demonstrate hydrotropism in plants.

Apparatus : Germinating pea seeds, porous pot, soil, water, etc.

Procedure :

1. Take a bigger vessel and fill it with soil.
2. Put some germinating seeds at one side and put a porous pot on the other side as shown in the figure.
3. Fill the porous pot with water regularly.

iv) Observe the setup after two to three weeks.

Observation :

After two to three weeks, we observe that the roots of seedling move towards the water (porous pot).

Conclusion :

Based on the above experiment, we can say that the roots exhibit hydrotropism (bend in the direction of water).

Q11. How does chemical coordination takes place in animals ?

Ans. Chemical coordination in animals takes place through chemicals secreted by endocrine glands called hormones.

Q12. Which of the following is a plant hormone ?

a) Insulin

b) Thyroxin

c) Oestrogen

d) Cytokinin

Ans. Cytokinin

Q13. Why is the use of iodised salt advisable ?

Ans.

1. Iodised salt or Iodine enriched salt contains iodine, which is necessary for the production of thyroxine hormone by thyroid gland.
2. Thyroxine regulates carbohydrate, protein and fat metabolism in the body.
3. Deficiency of iodine in diet can cause ‘Goitre’.
4. Hence, doctors advise to take Iodised salt.

Q14. The gap between two neurons is called a :

1.  dendrite
2. synapse                  
3. axon                    
4. impulse

Ans. Synapse

Q15. How does our body respond when adrenaline is secreted into the blood ?

Ans. When adrenaline is secreted into the blood :

1.  the heart beats faster, resulting in the supply of more oxygen to our muscles.
2. the blood flow towards digestive system and skin is reduced due to contraction of muscles   around small arteries in these organs. This diverts the blood to our skeletal muscles.
3. breathing rate also increases because of the contraction of the diaphragm and the rib muscles.
4. all these responses together enable the animal body to be ready to deal with the situation.

Q16. The brain is responsible for :

1. thinking
2. regulating the heart beat
3. balancing the body
4. all of the above

Ans.  all of the above

Q17. 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.

• Receptors are the cells that detect the changes in chemical and physical conditions of external and internal environment of an organism.
• Examples of receptors are thermo-receptors, pain-receptors, chemo-receptors and photo-receptors.
• Example of situations where receptors do not work properly is when we suffer from common cold, we can not smell the things properly.
• If receptors do not work properly, the external stimulus can not stimulate receptors and no nerve impulse would be generated.
• The result would be that the body will not respond to such changes in the surroundings.

Q18. Why are some patients of diabetes treated by giving injections of insulin ?

Ans.

• The blood sugar levels are regulated by a hormone secreted by pancreas called ‘Insulin’.
• If insulin is not secreted in sufficient amounts, the sugar level in the blood rises, causing many harmful effects.
• Hence, some of the patients of diabetes are treated by giving injections of insulin.

Q19. Draw the structure of a neuron and explain its function.

Ans.

Functions :

• They carry information from receptors to brain and spinal cord.
• They transfer responses from brain and spinal cord to effectors.

Q20. How does phototropism occur in plants ?

Ans.

• Phototropism is a movement or growth of plants in response to light.
• Auxins are responsible for the phototropism in plants
• Sunlight destroys auxins. Therefore, the side of shoot tip exposed to direct sunlight will have least amount of auxin. Whereas more auxins will be present on the shaded side.
• Phototropism is caused by increased auxin on shaded side and decreased auxin on illuminated side.
• Increased auxin causes increased growth in shoot (towards light).

Q21. Which signals will get disrupted in case of a spinal cord injury?

Ans.

1. The sensory and motor impulses from brain to body parts and vice versa.
2. Signals of reflex arc.  

Q22. How does chemical coordination occur in plants ?

Ans. Coordination of developmental process in plants is through small chemical molecules called as plant growth substances (phytohormones).

Q23. What is the role (is the need) of control and coordination in an organism ?

Ans.

• The body of a multicellular organism consists of a number of components (organ systems) and sub components (organs), each specialised to perform a particular function.
• However, all the components are not required to function all the time at the same speed.
• A system of control is required to allow them to perform, slow down or speed up their working. Further, most activities require the simultaneous or sequential functioning of a number of parts, stopping some and stimulating others.
• For example during feeding, eyes locate the food, nose recognises its smell, hands pick up the food and take it to mouth, mouth opens to receive the food, teeth and muscles take part in its mastication and saliva moistens it. Tongue perceives its taste.
• It aids in moving food in the mouth, chewing and swallowing. All this is possible only through a system of coordination.

Q24. How are involuntary actions and reflex actions different from each other ?

Ans.

Q25. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Ans.

Both nervous and hormonal mechanisms are helpful for  control and coordination in animals.

Q26. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs ?

Ans.