NCERT Solutions for Class 10th Science
Chapter 7 – CONTROL AND COORDINATION
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
Q.1 What is the difference between a reflex action and walking?
Ans A Reflex action is a sudden, automatic response to a stimulus i.e. we do something without thinking about it, or without feeling in control of our reactions. For eg. automatically pulling back of hand when kept on flame.
On the other hand walking is a voluntary action which is controlled by brain.
Q.2 What happens at the synapse between two neurons?
Ans Synapse is the gap between two neurons (axon ends of one neuron and dendrites of next neuron). It allows impulse transmission between neurons. The chemicals released by the axon ends of a neuron cross the synapse and start an electric impulse in the dendrites of the next neuron.
Q.3 Which part of the brain maintains posture and equilibrium of the body?
Ans Cerebellum, a part of hind-brain maintains posture and equilibrium of the body.
Q.4 How do we detect the smell of an agarbatti (incense stick)?
Ans The olfactory receptors present in our nose on receiving the smell, sends information in the form of electric impulse to the fore-brain which finally interprets the information and we detect the smell of an agarbatti (incense stick).
Q.5 What is the role of the brain in reflex action?
Q.6 What are plant hormones?
Q.7 How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Q.8 Give an example of a plant hormone that promotes growth.
Ans Auxin is a plant hormone that promotes growth.
Q.9 How do auxins promote the growth of a tendril around a support?
Ans A hormone called auxin, synthesised at the shoot tip, helps the cells to grow longer. When tendrils which are sensitive to touch come in contact with a support, auxin diffuses towards part that is away from support (contact). This concentration of auxin stimulates the cells to grow longer on the tendril part away from support and hence causes tendril to circle around the support and thus cling to it.
Q.10 Design an experiment to demonstrate hydrotropism.
Ans Hydrotropism may be defined as the directional growth movement of plant parts in response to the water. Experiment to show hydrotropism:
1. Take a tray and fill it with some soil (approx. 2 cm)
2. Now place a lima bean seed on the soil and cover it with another 2 cm layer of soil.
3. Keep the soil moist, not wet such that water does not reach the bottom of the soil and remains on surface only.
4. After a week, one will find small roots poking straight down and abruptly turning sideways. The downward growth (geotropism) shows roots responding to the pull of gravity. But the sideways growth (hydrotropism) indicates their search for surface water, essential to survival.
Q.11 How does chemical coordination take place in animals?
Q.12 Why is the use of iodised salt advisable?
Q.13 How does our body respond when adrenaline is secreted into the blood?
Q.14 Why are some patients of diabetes treated by giving injections of insulin?
EXERCISES
Q.1 Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Ans (d) Cytokinin
Q.2 The gap between two neurons is called a
(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.
Ans (b) synapse
Q.3 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
Q.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?
Q.5 Draw the structure of a neuron and explain its function.
Q.6 How does phototropism occur in plants?
Q.7 Which signals will get disrupted in case of a spinal cord injury?
Q.8 How does chemical coordination occur in plants?
Q.9 What is the need for a system of control and coordination in an organism?
Q.10 How are involuntary actions and reflex actions different from each other?
Ans Involuntary actions: These are the actions over which we do not have any thinking control. For eg. blood pressure, salivation, vomiting etc. are the involuntary actions which are directly controlled by the mid- brain and hind-brain.
Reflex actions: These are sudden, automatic responses to a stimulus and are not processed by brain. For eg. size of the pupil changes when exposed to sudden light is the response of eye towards light which does not involve thinking and is controlled by spinal cord.
Q.11 Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Q.12 What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?