parasympathetic nervous system Part of the autonomic nervous system. Its nerve endings release acetylcholine as a neurotransmitter and its actions tend to antagonize those of the sympathetic nervous system. For example, the parasympathetic nervous system increases salivary gland secretion, decreases heart rate, promotes digestion (by increasing peristalsis), and dilates blood vessels, while the sympathetic nervous system has opposite effects.

parasympathetic nervous system That part of the autonomic nervous system which generally causes bodily functions to become appropriate for calm conditions, for instance by slowing down the heart rate and promoting digestion. Nerves of the parasympathetic nervous system tend to form ganglia (ganglion) at the effector organ such that preganglionic fibres from the spinal cord are long, postganglionic fibres are short. The nerve endings of the parasympathetic nerve system are cholinergic.

parasympathetic nervous system (pa-ră-sim-pă-thet-ik) n. one of the two divisions of the autonomic nervous system, having fibres that leave the central nervous system from the brain and the lower portion of the spinal cord and are distributed to blood vessels, glands, and internal organs. It is responsible for (among other effects) slowing the heart rate and constricting the pupillary muscles. The nerve endings release acetylcholine as a neurotransmitter.