Cardiac innervation (anatomy)

The innervation of the heart originates from the cardiac plexuses which contain both afferent and efferent autonomic fibres. The cardiac nerves which supply the plexuses and their central connections are considered in the submenu.

Nerve fibres from the plexuses are distributed to the:

• sinuatrial node:
  • cholinergic parasympathetic fibres are positively chronotropic
  • adrenergic sympathetic fibres are negatively chronotropic
• atrioventricular node and bundle: sympathetic fibres are positively chronotropic by increasing the speed of conduction through these structures
• atrial and ventricular myocardium:
  • sympathetic fibres are positively inotropic, parasympathetic fibres have the opposite effect
  • the atria have a denser innervation than the ventricles
  • the sympathetic innervation to the ventricles is denser than the parasympathetic supply
• coronary arteries:
  • sympathetic fibres cause vasodilatation
  • parasympathetic fibres cause vasoconstriction

Afferent fibres from the coronary arteries, the subendocardial surfaces of the atria and ventricles, the venae cavae and the pulmonary veins, probably travel to the cardiac plexuses by both sympathetic and parasympathetic routes.

The synapse between the autonomic fibres and myocytes may be either a close proximity between the two or discrete neuromuscular junctions similar to those seen in skeletal muscle.