Parasympathetic nerves (lung)

The parasympathetic supply to the lungs travels via the vagus nerve and is relayed via the pulmonary plexus. From the plexus on each side, parasympathetic fibres pass into the lungs around pulmonary arteries; the ramification of the arteries is accompanied by a similar divergence of nerve fibres.

The pulmonary parasympathetic nervous system has both an afferent and an efferent division:

• afferent nerves:
  • general visceral sensory fibres pass superiorly with their cell bodies in the inferior ganglion of the vagus to synapse in the nucleus solitarius of the medulla
  • receptors include unmyelinated free nerve endings in the subepithelial layer of the bronchial tree
  • serve the sensations of touch and pain
  • involved in the afferent limb of the cough reflex
• efferents:
  • cell bodies in the dorsal motor nucleus of the vagus nerve within the medulla
  • synapse with nerves in the walls of the bronchial mucosa
  • act on smooth muscle of bronchi and bronchial arterioles to cause contraction
  • produce bronchoconstriction and vasoconstriction