parasympathetic nervous system

Last reviewed 01/2018

The parasympathetic component of the autonomic nervous system has a restorative function, returning tone to the basal level after excitation.

Also known as the craniosacral system, the fibres run in cranial nerves III, VII and X, and in the sacral nerves to their respective ganglia: NERVE / SEGMENT GANGLION / GANGLIA III ciliary VII { geniculate, { pterygopalatine { submaxillary { otic IX otic X thoracoabdominal viscera S2, S3 vesical & enteric

The ganglia are viscerally sited, i.e. are distant from the spinal cord close to the innervated viscera. Hence, the preganglionic fibres are long while the post-ganglionic fibres are short.

The effector transmitter from the postganglionic fibres is acetylcholine. The visceral ganglion implies a more refined system than the sympathetic, with more local control.

The afferent fibres of the parasympathetic system reach the central nervous system through the vagus nerve.