Body functions stimulated by the parasympathetic nervous system (PSNS) include sexual arousal, salivation, lacrimation, urination, digestion, and defecation. The PSNS primarily uses acetylcholine as its neurotransmitter. Peptides (such as cholecystokinin) may also act on the PSNS as neurotransmitters. The parasympathetic nervous system is composed mainly of the cranial and sacral spinal nerves.
