Control And Coordination(Question Answer)

QUESTIONS

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

Answer: Difference between a reflex action and walking are-

Reflex Action	Walking
1. This is an involuntary action	1. This is a voluntary action
2. It is controlled by the spinal chord	2. It is controlled by the brain
3. Response occurs spontaneously	3. Response is based on thoughts.

2. What happens at the synapse between two neurons? 

Answer: The information, acquired at the end of the dendritic tip of a nerve cell  sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland.

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

Answer: Cerebellum maintains posture and equilibrium of the body.

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

Answer: The smell of incense stick diffuses through the air. The olfactory nerves in our nose receive these sensations and the sensory nerves transmit these sensations to the brain. Which helps us detect the smell of an incense stick.

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

Answer: Brain has no role in reflex action. It is controlled by spinal chord. 

6. What are plant hormones? 

Answer: Plant hormones are chemical substances which help in the growth and development of plants and in maintaining control and coordination in plants. Some of the hormones found in plants are auxin, gibberellins, Cytokinins and Abscisic acid.

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

Answer: The movement of the leaves of sensitive plant is due to the affect of the touch stimulus, it does not depend on the direction of the stimulus. This movement is instantaneous. On the other hand, the movement of the shoot towards light is due to the action of light stimulus, which depends on the direction of stimulus i.e. the direction of light. This movement is very slow.

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

Answer: A plant hormone that promotes growth is 'Auxin'.

9. How do auxin promote the growth of a tendril around a support? 

Answer: Some plants like the pea plant climb up other plants or fences by means of tendrils. These tendrils are sensitive to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it.

10. Design an experiment to demonstrate hydrotropism.

Answer: The movement of a plant's root towards water is called hydrotropism.

                             A seedling of any kind of plant was planted in a pot with a little soil. A small amount of water was placed in a perforated vessel at a distance from the seedling. If this arrangement is left for a few days, the roots of the plant will bend towards the water container as shown in the figure.

11. How does chemical coordination take place in animals? 

Answer: The chemical coordination in animals is controlled by hormones secreted by the endocrine glands. The hormones and the nervous system combine to form the endocrine system and this endocrine system perform chemical coordination in animal body. The endocrine glands secrete hormones directly into the bloodstream. Blood carry the hormones to specific cells. These cells identify the hormones and act on the instructions given by the hormones.

12. Why is the use of iodized salt advisable? 

Answer: Thyroxin hormone regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxin. In case iodine is deficient in our diet, there is a possibility that we might suffer from goitre. Hence use of iodized salt is advisable.

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

Answer: Adrenaline is secreted directly into the blood and carried to different parts of the body. The target organs or the specific tissues on which it acts include the heart. As a result, the heart beats faster, resulting in supply of more oxygen to our muscles. The blood to the 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. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the situation.

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

Answer: The pancreas secretes a hormone insulin, which is responsible for regulating the level of glucose in blood. If required amount of insulin is not secreted, the amount of glucose in the blood can increase significantly. This causes considerable damage to the body and this situation is called diabetes. Some diabetes patients are given insulin injection to maintain adequate levels of insulin in the blood.

EXERCISES 

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 heart beat. 

(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: The receptor organs are the special cells that are found in the sensitive parts of our body such as the inner ear, nose and tongue. These organs help to perceive all the messages or stimuli of the external environment.

     If the receptors do not function properly, then all the messages from the external environment will not be delivered to the nerves and brain in time.

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

Answer:

        All information from our environment is detected by the specialized tips of neurons. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell. This information, acquired at the end of the dendritic tip of a nerve cell, sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland.

 6. How does phototropism occur in plants? 

Answer: Environmental triggers such as light can change the directions that plant parts grow in. Such movement of parts of plant in response of light is called phototropism. These directional, or tropic, movements can be either towards the light, or away from it. So, in two different kinds of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.

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

Answer: Involuntary actions are disrupted when there is a spinal chord injury. In addition, there is a disruption in the reflex actions because these events are controlled by the spinal chord.

8. How does chemical coordination occur in plants? 

Answer:  Chemical coordination in plants is caused by hormones. In some parts of the plant body where cell division takes place, certain stimulating cells secrete hormones. These hormones identify the messages and transmits it to the neighboring cells.

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

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

(i) To save organisms from the harmful changes in the environment.
(ii) To control voluntary and involuntary actions.
(iii) 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? 

Answer: Difference between involuntary actions and reflex actions are-

Involuntary Action	Reflex Action
1. Involuntary actions occur immediately without any thinking involved.	1. Reflex action is the immediate response to any stimuli without the involvement of brain
2. It is controlled by the mid and hind brain	2. It is controlled by the spinal chord

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

Answer:

Nervous Mechanism	Hormonal Mechanism
1.       It is a rapid process	1.       It is slow process
2.        It transmits in electro- chemical form	2.          It transmits in chemical form
3.       3. It does not affect growth and development of organism	3.       It affects the growth and development of organism

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	Movements in our leg
1. It happens in response of touch	1. It is a voluntary action
2. It is an involuntary action	2. It is controlled by brain
3.        This type of  movement occurs due to change of concentration of water in cells.	3.        There is no role of concentration of water in cells.