Question

A cylindrical structure P in our body begins in continuation with medulla and extends downwards. It is enclosed in a bony cage Q and surrounded by membranes R. As many as x pairs of nerves arise from the structure P. The structure P is involved in the reflex actions of our body and conduction of nerve impulses to and from another organ S of our body with which it forms CNS.
(a) Name the structure P.
(b) Name (i) bony cage Q, and (ii) membranes R.
(c) How much is x?
(d) Name the organs S.
(e) What are the reflexes involving structure P only known as?

Answer 1

(a) The structure P is the spinal cord. It is a cylindrical structure that begins in continuation with the medulla and extends downwards.
(b) (i) The bony cage Q is the vertebral column. The spinal cord is enclosed by the vertebral column.
(ii) R represents the meninges. The spinal cord is surrounded by membranes called the meninges.
(c) x represent the number of pairs of spinal nerves. They are 31 in number.
(d) S is the brain. The central nervous system consists of the brain and the spinal cord.
(e) The reflex actions involving the spinal cord (P) are known as spinal reflexes.