Nerve supply to the lung
The innervation of the lung remains incompletely understood. Parasympathetic (from the vagus) and sympathetic (from the adjacent sympathetic chain) nerve supplies entwine in a plexus at the nerve root and branches accompany the pulmonary arteries and the airways. Airway smooth muscle is innervated by vagal afferents, postganglionic muscarinic vagal efferents and vagally derived non-adrenergic non-cholinergic (NANC) fibres. Neurotransmitters (peptides and purines) may be involved. Three muscarinic receptor subtypes have been identified: M1 receptors on parasympathetic ganglia, a smaller number of M2 receptors on muscarinic nerve terminals, and M3 receptors on airway smooth muscle. The parietal pleura is innervated from intercostal and phrenic nerves but the visceral pleura has no innervation.