What is the role of the AV node in heartbeat conduction?

• A. Delays impulses to ensure the atria are empty
• B. Delays spreading the impulses for 0.1 second to allow the atria to empty
• C. Initiates impulses that cause ventricular contraction
• D. Conducts impulses to Purkinje fibers

Answer: (B)

The key idea is that the AV node slows the electrical signal so the atria have time to finish contracting and push blood into the ventricles before the ventricles contract. This pause lasts about 0.1 second, giving the atria a moment to empty and ensuring coordinated filling of the ventricles. After this delay, the impulse moves from the AV node to the bundle of His and then to Purkinje fibers to drive the ventricles.

The AV node’s main job is this delay. It doesn’t initiate impulses (that’s the SA node), and while it does pass the signal along to the ventricles via the conduction system, the defining feature is the deliberate slowing that coordinates atrial and ventricular beats.