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Portrait of Vagus nerve

Anatomy · Brain & nerves

Vagus nerve

Cranial nerve X — Latin 'wandering'

Cranial nerves · parasympathetic

The tenth of the twelve pairs of cranial nerves and the longest of them, wandering from the medulla through the neck and chest into the abdomen. It is the main channel of the parasympathetic nervous system, slowing the heart and driving digestion, and it also carries sensation from the throat, thoracic organs and gut back to the brain. Its Latin name means 'wandering'.

How to spot them

  • ▸A long nerve leaving the skull through the jugular foramen and running down the neck in the carotid sheath
  • ▸Passes through the chest beside the oesophagus and enters the abdomen with it, through the diaphragm
  • ▸Gives off a branch that loops under the aortic arch on the left (under the subclavian artery on the right) before climbing back to the voice box
  • ▸Fibres from it slow the heart; cutting it in the abdomen was once a treatment for stomach ulcers

What to know

Cranial nerve X, and the longest of the twelve

Vagus nerve — the tenth cranial nerve, the 'wandering' one.

Its Latin name means 'wandering', for its long course from the head to the abdomen

Vagus nerve — from vagus, wandering.

Stimulating it slows the heart; in 1921 a frog-heart experiment showed it releases a chemical, the first neurotransmitter identified

Vagus nerve — Otto Loewi's 'Vagusstoff' (acetylcholine).

A branch on the left loops under the aortic arch before climbing to the larynx, a detour taken to its extreme in the giraffe

Vagus nerve — the recurrent laryngeal branch.

Overactivity of it, with a sudden fall in heart rate and blood pressure, causes fainting at the sight of blood

Vagus nerve — vasovagal syncope.

An implanted pacemaker-like device that stimulates it in the neck is used to treat epilepsy and depression that resist drugs

Vagus nerve — vagus nerve stimulation.

It supplies the muscles of the soft palate and pharynx, and the gag reflex uses it as its motor limb

Vagus nerve — the glossopharyngeal is the sensory limb.

Its operative division was once a standard treatment for peptic ulcer, cutting acid secretion

Vagus nerve — vagotomy.

Key ideas

  • It is mostly a sensory nerve: roughly 80 per cent of its fibres carry information from organs to brain, not the other way round (a commonly cited figure).
  • It supplies the parasympathetic 'rest and digest' drive to the heart, lungs and most of the gut.

Quick-fire facts

  • •Cranial nerve X; the twelve pairs are olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), accessory (XI) and hypoglossal (XII)
  • •Classic mnemonic for the twelve: 'Oh Oh Oh To Touch And Feel Very Good Velvet, Ah Heaven'
  • •Leaves the skull via the jugular foramen and descends in the carotid sheath
  • •Its recurrent laryngeal branches supply all intrinsic muscles of the larynx except cricothyroid; the left loops under the aortic arch, the right under the subclavian artery
  • •Otto Loewi's 1921 frog-heart experiment on 'Vagusstoff' led to a share in the 1936 Nobel Prize with Henry Dale
  • •Provides parasympathetic supply to the heart, lungs and gut as far as roughly the splenic flexure of the colon
  • •Vagus nerve stimulation is approved for some forms of epilepsy and depression
  • •The vagus is often quoted as carrying about three-quarters of all parasympathetic fibres
  • •Vasovagal syncope, the common faint, is a reflex involving the vagus

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Sources