Communications between stimulus and response take place due to the nervous system present in our body. The nervous system of man consists of a brain, spinal cord, and nerves associated with the brain and spinal cord.
A- STRUCTURE OF BRAIN
1- The brain consists of very delicate nerve cells and is protected by the skull. The brain is enclosed within a thin membrane called the Pia matter. Internally the skull is lined by a membrane called the dura matter. The fluid is present between these membranes which protect the brain from shocks.
2- The brain has three regions
- Medulla Oblongata
(1) THE CEREBRUM
It is also called the forebrain. It is the largest part and is divided into two halves called cerebral hemispheres. It is composed of deeply folded delicate nerve tissues. The outer part is composed of white matter. There are numerous nerve fibers present in the central part of the cerebrum.
The forebrain does most of the thinking and coordinates activities of the body. It is also called the seat of intelligence.
(2) THE CEREBELLUM
This part of the brain is also called the mid-brain. It is much smaller than the forebrain and is deeply folded.
This part of the brain performs the balancing functions of the body. It controls voluntary actions for example we can take our finger correctly toward our nose.
(3) THE MEDULLA OBLONGATA
It is also called the bind brain. It is a small elongated part of the brain which links the spinal cord with the brain.
The medulla contains the centers of the nervous group which controls the rate of breathing and pumping heart and circulation of blood and digestion of food.
Any blow on the medulla oblongata makes a person unconscious.
B- SPINAL CORD
The spinal cord is present inside the vertebrae of the backbone. It receives unpulses from different organs through nerves and sends them to the brain.
It is also controlled reflex actions that do not involve the brain. The spinal cord gives off 31 pairs of spinal nerves which form a complex network in the body.