In the cardiac conduction system, which node delays impulses to allow atrial contraction before ventricular contraction?

• A. SA Node
• B. AV Node
• C. Purkinje Fibers
• D. Bundle of His

Answer: (B)

Timing between atrial and ventricular contractions is controlled by a deliberate delay in the heart’s conduction system. The impulse starts in the sinoatrial node, which acts as the natural pacemaker, and travels through the atria to the atrioventricular node at the junction of the atria and ventricles. The AV node slows the impulse, creating the pause that lets the atria finish contracting and fill the ventricles with blood. After this delay, the impulse moves rapidly through the Bundle of His and the Purkinje fibers to trigger ventricular contraction. The other components mainly conduct signals quickly and do not create this essential pause; the SA node initiates the signal, while the Purkinje fibers and Bundle of His propagate it to the ventricles.