ABSTRACT
The nervous system is comprised of the central nervous system (CNS) and peripheral nervous system (PNS). The CNS includes the brain and spinal cord. The PNS is everything else: namely nerve trunks going between the CNS and the periphery, and the networks of nerve cells with supporting glia in organs throughout the body. The somatic nervous system structure reflects both the bilateral symmetry and segmented nature of the vertebrate body plan. However the activities of the autonomic nervous system (ANS) are modified by sensory input that travels by way of the somatic nervous system and by the CNS. In the sympathetic system, divergence may be achieved by direct synapses, via interneurons or via the local diffusion of transmitter. The enteric nervous system can act autonomously to coordinate gut motility and secretion. Its activity is modified by input from both divisions of the ANS.
