Innervation of coronary arteries

• • So, in addition to responding to metabolic factors as described previously the calibre of the coronary arteries (and therefore blood flow), is also regulated by the autonomic nervous system
  • Predominantly the coronary arteries are regulated by the sympathetic nervous system only
  • So, increased sympathetic activity tends to increase vasodilation (acting via β2 receptors) and enhanced blood flow / myocardial O2 provision
  • Reducing sympathetic activity tends to reduce vasodilation and hence in effect to cause vasoconstriction and reduce coronary blood flow and myocardial perfusion
• • However, putting the metabolic and sympathetic mechanisms together and thinking are they both of equal importance, we need to recognise that on exercise the altered metabolic status of the heart is the biggest driver of coronary artery vasodilation and therefore myocardial perfusion
  • However, the sympathetic nervous system still provides a valuable vasodilatory effect
  • Both metabolic and sympathetic nervous system induced vasodilation on exercise helps to ensure optimal cardiac function and to minimise the risk of ischaemia