(a) Name the three types of nerves which constitute the peripheral nervous system.
(b) What is the difference between a reflex action and walking?
(c) How do we detect the smell of an incense stick (agarbatti)?
(a) The three types of nerves which make up the peripheral nervous system are: spinal nerves, cranial nerves and visceral nerves.
(b) Reflex action: It is a rapid, automatic response to a stimulus which is not under the voluntary control of the brain. It is a kind of involuntary action which involves the spinal coed. It is not based on our thinking.
Walking: It is a voluntary action which we undertake knowingly. The action of walking involves thinking by the brain. The central nervous system (brain, spinal cord) takes part in the action of walking.
(c) When the agarbatti burns, it produces vapours having a characteristic pleasant smell which is detected by the olfactory receptors present inside our nose. The action of smell of agarbatti or receptors sets off chemical reactions which generate electrical impulses. The sensory neurons carry these electric al impulses to the sensory area of fore brain called cerebrum. This makes us detect the smell of burning agarbatti.