The complex part of an animal is the nervous system in the body, transmit sensory information to different parts of its body. There are two main parts in the vertebrates, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord while the PNS consists of nerves which are long fibers and connect the CNS to every other part of the body.

There are two types of Nerves, Motor nerves that transmit signals from the brain and sensory nerves that transmit information from the body to the CNS. Spinal nerves perform both functions called mixed nerves.

The nervous system divided into two categories:
neurons and glial cells.