The central
nervous system is a delicate structure composed of the brain and the spinal
cord. The brain is protected by a bony structure called the cranium or skull and the spinal cord by the vertebral
column or the back bone. Protective membranes called the meanings are present
in the space between the soft CNS and the bone. There are cavities present on
the different parts of the brain known as ventricles while the long cavity of
the spinal cord is called the central canal. The ventricles, central canal and
the space between the meanings are filled with cerebrospinal fluid (CSF). CSF
keeps the CNS well nourished and also protects it by absorbing mechanical
shocks.
Many of our actions are voluntary in nature i.e. we think
before doing it, like walking, clapping hands, bending down to pick up
something, etc. In all these actions there is involvement of our muscles. The
brain sends message to the muscles and the muscles act accordingly. This is the
second instance where the nervous system is communicating with the muscles.
Such a communication between the central
nervous system and the other parts of the body is brought about by the
Peripheral Nervous System (PNS) which is composed of cranial nerves arising
from the brain and the spinal nerves arising from the spinal cord. The brain
makes us think and we act based on our thinking. We infer that the brain must
be a complex structure with different centres responsible for integrating
various inputs and outputs. The brain is a complex organ divided in three
regions forebrain, midbrain and the hind brain.
The forebrain
or the cerebrum is the main thinking part of the brain. It has regions which
receive the sensory impulses from various receptors.
