ABSTRACT
The autonomic nervous system (ANS) is the other part of the peripheral nervous system. It has sensory and motor functions for the internal organs and glands. These tend not to be under voluntary control, and many of the muscles innervated by this system are made of smooth muscle rather than skeletal muscle. This has a different structure and different properties to the muscles that are attached to our skeleton. The ANS has two distinct branches, the sympathetic nervous system and the parasympathetic nervous system. In both systems the neurons that innervate the target organs leave the spinal cord and then make a single synapse before reaching the target organ. The systems also differ with respect to where the fibers leave the spinal cord. The sympathetic fibers all emerge from thoracic and lumbar sections of the spinal cord whereas the parasympathetic fibers come from the cranial and sacral portions of the cord.
