The portion of the vertebrate nervous system consisting of the brain and spinal cord; SYN. CNS.
(CNS) The 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.