5.Control and Coordination

Question of page – 119

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


i) A reflex action is a spontaneous involuntary one channel response to a stimulus by our voluntary organs.

 ii) Walking is a voluntary action controlled by our brain.

Q.2 what happens at the synapse between two neurons?

Ans.At the synapse between two neurons the electrical impulse reaches thin and release chemicals called neurotransmitter.

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

Ans.Cerebellum maintains posture and equilibrium of the body.

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

Ans. We detect the smell of an agarbatti with the help of olfactory receptors present in the sense organ in the forebrain.

Q.5 what is the role of the brain in reflex action?

Ans. The reflex actions are controlled by spinal cord and the message reaches to the brain. Hence brain is the coordinating center. Both brain and spinal cord coordination with each other control all voluntary & involuntary action.


                                     Question of page – 122

Q.1 what are plant hormones?

Ans.These chemicals which are secreted by plants which are responsible from the growth of the plants. These chemicals are called plant hormones. E.g. – Auxins Gibberlins

Q.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 plants is not in one direction, they show nastic movement but movement of a shoot towards light is in one direction i.e. tropical movement.

Q3. Give an example of a plant hormone that promotes growth.

Ans.The plant hormone that promotes growth is cytokines.

Q4. How do auxins promote the growth of a tendril around a support?

Ans. As we know auxins present in the plant cells helps to grow longer. 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 fast as the part of the tendril away from the tendril. This helps tendril to circle around the object.

Q5. Design an experiment to demonstrate hydrotropism.

Ans. It is a darning.

                            Question & Answer of page 125.

Q1.How does chemical coordination take place in animals?

Ans.The chemicals co-ordination take place in animals through chemicals messenger called hormones. These hormones secreted by endocrine gland. These hormones are carried by the blood to the site of action to archive the desired effect.

Q2.Why is the use of iodized salt advisable?

Ans. Iodized salt is advised to use because it consist Iodine, which is essential for the thyroid gland to make thyroxin hormones. Thyroxin regulates carbohydrates, protein and fat metabolism in the body. Its deficiency leads to a disease called goiter.

Q3.How does our body respond when adrenaline is secreted into the blood?

Ans.Adrenaline is secreted directly into the blood and carried to different parts of the body. The following action occurred - 

I.)           The heart beat faster in order to supply more o2 to our muscles.

II.)          The blood to the digestive system and skin is reduced and the breathing rate increases.

All these responses together enable the animal’s body to be ready to deal with the situation.

Q4. Why are some patients of diabetes treated by giving injections of insulin?

Ans.Some patients of diabetes are treated by giving injection of insulin because insulin is a hormone. Which is produced by the pancreas and helps in regulating blood sugar levels? If it is not secreted in proper amount the sugar level in the body rises resulting many harmful effects.

                               Question of page – 125

Q1. Which of the following is a plant hormone?

(a) Insulin

(b) Thyroxin

(c) Oestrogen

(d) Cytokine.

Ans.   d) Cytokine

Q2. The gap between two neurons is called a

(a) dendrite.

(b) synapse.

(c) axon.

(d) impulse.

Ans.   b) Synapse

Q3. The brain is responsible for

(a) thinking.

(b) regulating the heart beat.

(c) balancing the body.

(d) all of the above.

Ans.   d) All of the above

Q4. 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.The function of receptor is to collect information from our environment and detect by the specialized tops of nerve cells.

When we are eating something, if we block our nose then we can not say much about the taste of the food we are eating. So without this receptor we can not enjoy our environment.

Q5.Draw the structure of a neuron and explain its function.

Ans. Our neuron is divided in three different parts (a) Cell body (b) Dendrites and Axon.

  1. Cell body: It consists of nucleus and cytoplasm. Again in cytoplasm are embedded numerous cell organelle like mitochondria, golgi apparatus, endoplasmic, reticulum.
  2. Dendrites: - These are short branches which convey the impulse towards the cell body.
  3. Axon: - These are in the form of an elongated fiber with terminal and fibers having swollen knobs. It conducts nerve impulses away from the cell body. It communicates with other neurons through synapse.

Q6. How does phototropism occur in plants?

Ans. Plants bend towards light when they are exposed to it from one side of long axis. These are shoot. These shoot are said to be positively phototropic and while roots are negatively phototropic as they grow away from light.

Q7. Which signals will get disrupted in case of a spinal cord injury?

Ans. Spinal cord is made up of nerves which supply information to thinle about. So massage to brain will get disrupted.

Q8. How does chemical coordination occur in plants?

Ans. Plants do not have nervous system. But then also they do show movement in response to external stimuli and show growth movements like bending, trusting, coiling and elongation. Plants growth and development is regulated by external factors and chemicals produced by them called plant hormones. It plant hormones coordinate the activities of cell and tissues.

Q9. What is the need for a system of control and coordination in an organism?

Ans. A system of control coordination is needed in an organism because it helps in development and proper growth of an organism. This system helps on organism to give response to external stimuli. It is also needed for interaction between the environment and individual himself. Organism can not survive without this system.

Q10. How are involuntary actions and reflex actions different from each other?

Ans. Involuntary actions happen without will or thinking but are continues action. Examples are heartbeat, blood flow. But reflex actions are the repaid automatic response, which happens on specific condition.

Q12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Ans. The monument in the sensitive plant is nastic non direction and sensitive      to touch. But movement in our legs is voluntary i.e. they act according to our well.



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