The nervous system is the means by which the body co-ordinates bodily
systems and informs the body about any changes in the environment.
The nerves carry brief electro-chemical messages that trigger appropriate responses in the various parts of the body. The messages (impulses) then react and will do certain tasks such as make the muscles contract, the glands secrete and the blood vessels widen or narrow.

The nervous system is a very complex system in the body but is divided
up into two main parts. The Central Nervous System (CNS) and the
Peripheral Nervous System (PNS).