What is Nervous System?

The nervous system is made up of associations of cells called neurons. Bundles of neurons are called nerves. The nervous system is divided into two parts: central and peripheral. The central nervous system consists of the brain and a spinal cord that extends down the dorsal part of the body. (The word ventral refers to the front of the body, dorsal refers to the back side, anterior, toward the head, and posterior, toward the tail or feet.) A cluster of neurons located outside of the central nervous system is called a ganglion (plural ganglia).

The peripheral nervous system contains nerves connecting the central nervous system to the rest of the body. Electrical signals from the peripheral nervous system are carried to the spinal cord and then to the brain, where they are interpreted, and signals are sent out in response through the spinal cord to target cells called effectors in glands or muscles.