The Parasympathetic Nervous System
The parasympathetic nervous system (PNS), along with the sympathetic nervous system (SNS) form the autonomic nervous system, regulating blood pressure, heart rate, resipration, water balance, and many other homeostatic functions.
The parasympathetic system can be thought to enhance energy storage, decreasing cardiac output and blood pressure, increasing peristalsis, etc.
Autonomic neurons control smooth and cardiac muscle, many glands, and some adipose tissue.
The parasympathetic neurons leave the spinal cord at the cranial and sacral (S2-4) levels
Some preganglionic PNS fibres terminate in ganglia outside their target organs, mostly in the head and pelvis. The majorty of preganglionic PNS fibres terminate on ganglia located on the wall of their target organ.