central nervous system

The central nervous system (CNS) with its associated nerves.

Brain and spinal cord, as distinct from other components of the nervous system. The CNS integrates all nervous function.

In invertebrates it consists of a paired ventral nerve cord with concentrations of nerve-cell bodies, known as ganglia in each segment, and a small brain in the head. Some simple invertebrates, such as sponges and jellyfishes, have no CNS but a simple network of nerve cells called a nerve net.