Wednesday, August 19, 2009

Atrioventricular Node

The atrioventricular node is a part of the cardiac conducting system and functions as an electrical relay station located between the right atrium and the right ventricle. The atrioventricular (AV) node coordinates heart rate. It electrically connects the atria and the ventricles. The AV node is an area of specialized tissue between the atria and the ventricles of the heart, specifically in the posteroinferior region of the interatrial septum near the opening of the coronary sinus, which conducts the normal electrical impulse from the atria to the ventricles. The AV node is quite compact (~1 x 3 x 5 mm). It is located at the center of Koch's Triangle—a triangle enclosed by the septal leaflet of the tricuspid valve, the coronary sinus, and the membraneous part of the interatrial septum.

The atrioventricular node is activated when a wave of excitation spreads out from the sinoatrial node through the atria along specialized conduction channels. The atrioventricular node delays impulses by approximately 0.12s. This delay in the cardiac pulse ensures that the atria have ejected their blood into the ventricles first before the ventricles contract.