Parasympathetic nervous system


Autonomic nervous system (ANS) consists of parasymphatetic nervous system (PSNS) and symphatetic nervous system (SNS). Parasympathetic nervous system is almost exclusively cholinergic, using acetylcholine (ACh) as the neurotransmitter.

Parasympathetic nerves arise from the central nervous system (CNS), mostly from the spinal cord. The efferent parasympathetic nerve signals are carried from the CNS to their targets by a system of two neurons: preganglionic (presynaptic) neuron and postganglionic (postsynaptic) neuron. The cell body of preganglionic neuron resides in the CNS, from where its long axons extend into a ganglion that is close to or embedded in the target organ. Accordingly, the postganglionic nerve fibres are short. The stimulated preganglionic neuron releases ACh at the ganglion, which acts on nicotinic acetylcholine receptors (nAChRs) of postganglionic neurons. The postganglionic neurons then releases ACh to stimulate the muscarinic acetylcholine receptors (mAChRs) of the target organ.

In pancreas, parasympathetic system stimulates insulin secretion, and sympathetic system stimulates glucagon secretion. Hypothalamus can regulate hepatic glucose production via PSNS.

See also:


Benarroch EE. Physiology and pathophysiology of the autonomic nervous system. Continuum (Minneap Minn) 2020; 26(1): 12-24. doi: 10.1212/CON.0000000000000817.

Gibbons CH. Basics of autonomic nervous system function. Handb Clin Neurol. 2019; 160: 407-418. doi: 10.1016/B978-0-444-64032-1.00027-8.

Imai J, Katagiri H. Regulation of systemic metabolism by the autonomic nervous system consisting of afferent and efferent innervation. Int Immunol. 2022; 34(2): 67-79. doi: 10.1093/intimm/dxab023.

Wehrwein EA, Orer HS, Barman SM. Overview of the anatomy, physiology, and pharmacology of the autonomic nervous system. Compr Physiol. 2016; 6(3): 1239-1278. doi: 10.1002/cphy.c150037.

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Updated at: 2023-01-17
Created at: 2017-10-07
Written by: Vesa Oikonen