Somatic and Autonomic Neural System

The peripheral neural system's outgoing (motor) pathways split into two systems with very different jobs. The somatic neural system (SNS), also called the voluntary neural system, is the part responsible for conscious control of body movement through the skeletal muscles; its sensory and motor nerves innervate striated muscle, and its main jobs are voluntary movement of muscles and organs plus certain reflex movements that still run through skeletal muscle.

The autonomic neural system (ANS), by contrast, is self-governing and largely automatic, controlled from the hypothalamus. It innervates smooth muscle, cardiac muscle and glands, and coordinates involuntary activity in organs the body does not consciously manage moment to moment — things like heart rate, digestion and pupil size. Structurally, it is built from three components in series: a preganglionic neuron, whose cell body sits in the brain or spinal cord and whose myelinated axon exits the CNS as part of a cranial or spinal nerve and ends at an autonomic ganglion; the autonomic ganglion itself, containing the preganglionic axon terminal together with the cell bodies of postganglionic neurons; and the postganglionic neuron, which actually carries the impulse onward from the ganglion to the visceral effector organ. …