How does the atrioventricular (AV) node contribute to the heart's conduction system?

• A. It initiates atrial contraction.
• B. It conducts impulses directly to the ventricles without delay.
• C. It delays the impulse to allow atrial contraction and ensures ventricles fill before they contract.
• D. It pumps blood into the systemic circulation.

Answer: (C)

The AV node acts as a gatekeeper in the heart’s electrical pathway, introducing a delay between atrial and ventricular activation. This built-in pause lets the atria complete their contraction and push blood into the ventricles, so the ventricles have optimal filling before they contract. After this delay, the impulse proceeds rapidly through the His-Purkinje system to synchronize ventricular contraction. In other words, the AV node slows the signal, not initiates it or pumps blood. It sits between the atria and ventricles and helps regulate the timing of the heartbeat.