Basics Regulation of Coronary Artery

• Regulation of coronary artery diameter:

  • The calibre of the coronary arteries is regulated by the combination of local factors and the autonomic nervous system
  • The artery’s lumen changes from slightly shut down (vasoconstriction – vasomotor tone) at rest to widely dilated on exercise
  • The main determinant of coronary calibre are local “environmental” factors
• ANS Regulation of coronary artery diameter:

  • In contrast, the influence of the autonomic nervous system on vessel calibre is comparatively weak
  • Although sympathetic innervation to blood vessels throughout the body tends to cause vasoconstriction, here in the coronary circulation, sympathetic activity results in vasodilation (acting via beta-2 receptors) and will enhance blood flow and therefore myocardial O2 provision
  • The effect of the parasympathetic system on the coronary circulation is also thought to be vasodilatory but extremely weak
• Local Environmental Factor Regulation of coronary artery diameter:

  • The main determinant of coronary calibre are local “environmental” factors
  • When physical activity levels increase and the heart works harder (raised heart rate & stroke volume) the myocardial fibres require more O2 but also produce more metabolic waste products such as; H+, K+, CO2+ and adenosine, which act on the arteries and result in vasodilation
  • In addition, local endothelial cells secrete nitric oxide (NO), prostacyclin, bradykinin, which contribute to vasodilation