OME Cardiac Modules Practice Test

The AV node serves as a gatekeeper that delays the impulse from the atria to the ventricles. This delay, about a tenth of a second, gives the atria time to finish contracting and the ventricles time to fill before they contract. It also protects the ventricles from being overwhelmed by very rapid atrial rates.

Initiating atrial contraction is the job of the SA node, not the AV node. Accelerating ventricular contraction is not the AV node’s function; the ventricular conduction system and intrinsic rates of ventricular tissue determine the speed of ventricular activation, with the AV node mainly slowing things down. Increasing heart rate via sympathetic input touches many parts of the system, but the primary role here is the deliberate slowing of conduction to coordinate atrial and ventricular activity.