Parasympathetic (craniosacral) outflow
Outflow · III, VII, IX, X S2–S4 N_N at ganglion ACh on M1–M3
Preganglionic neurones lie in the brainstem nuclei of cranial nerves III, VII, IX and X and in the sacral cord at S2–S4. Long cholinergic preganglionic fibres synapse in ganglia in or beside the target, so postganglionic fibres are short and responses are discrete rather than mass.
Detail
- Cranial component
- Edinger–Westphal (III), superior salivatory (VII), inferior salivatory (IX), dorsal motor nucleus of vagus and nucleus ambiguus (X)
- Sacral component
- S2–S4 lateral grey → pelvic splanchnic nerves
- Postganglionic transmitter
- Acetylcholine on muscarinic receptors: M2 heart, M3 smooth muscle and glands
- Share of outflow
- The vagus carries roughly three-quarters of all parasympathetic fibres
When it goes wrong
Organophosphate (pesticide, nerve agent) inhibits acetylcholinesterase at every muscarinic synapse
Cholinergic crisis — salivation, lacrimation, urination, diarrhoea, bronchorrhoea with bronchospasm, bradycardia and miosis (DUMBELS); treat with atropine to effect and pralidoxime
Practise this structure
1 question in the bank tagged Autonomic.