What is nervous system?

Within the body the nerves branch out like telephone wires from an exchange. 
They run to every part of the body, from the soles of the feet to the top of the scalp 
and from just below the skin to the inner organs such as the heart, liver and lungs.
Nerve cells have the same basic structure as all the other body cells, with a surrounding 
membrane containing the nucleus and cytoplasm, but they have a very special, elongated shape. 
A typical motor nerve, carrying instructions from the brain to the muscle, has a tuft of short, 
root like projections, called dendrites, at one end. At the other end is a long, 
thin projection, called the axon.Most nerves act as links in a chain of nerve cells 
rather than connecting directly to a muscle. In such a chain, each axon is in near contact 
with the dendrites of the next cell, but there is a tiny gap between them. Nerve impulses 
jump this gap with the help of chemical messengers known as neurotransmitters.
The system has two main divisions: The central nervous system (CNS), 
which consists of the brain and the spinal cord, and the peripheral nervous system, 
which includes all the nerves that connect the CNS to every organ and area of the body.