parasympathetic nervous system
one of two branches of the autonomic nervous system (ANS), the other being the sympathetic nervous system. Anatomically it comprises the portion of the ANS whose preganglionic fibers leave the central nervous system from the brainstem via the oculomotor, facial, glossopharyngeal, and vagus nerves and from the spinal cord via three sacral nerves (see spinal nerve). It is defined functionally as the system controlling rest, repair, enjoyment, eating, sleeping, sexual activity, and social dominance, among other functions. The parasympathetic nervous system stimulates salivary secretions and digestive secretions in the stomach and produces pupillary constriction, decreases in heart rate, and increased blood flow to the genitalia during sexual excitement. Also called parasympathetic division.