The AV node is which structure?

• A. Atrioventricular node
• B. Sinoatrial node
• C. Purkinje fibers
• D. Bundle of His

Answer: (A)

The key idea is that the structure described is the atrioventricular node, a critical part of the cardiac conduction system. It sits in the lower part of the right atrial septum, within the triangle of Koch, near the tricuspid valve. Its main job is to receive the electrical impulse from the atria (generated by the SA node) and introduce a purposeful delay before passing it on to the ventricles. That delay gives the atria time to contract and complete ventricular filling before the ventricles are stimulated to contract, coordinating the timing of the heartbeat.

Understanding the other structures helps differentiate them: the sinoatrial node is the natural pacemaker located high in the right atrium near the superior vena cava, setting the rhythm. The band of tissue known as the bundle of His serves as the main pathway conducting the impulse from the AV node into the ventricles, continuing as the left and right bundle branches through the interventricular septum. Purkinje fibers form the terminal network that distributes the impulse throughout the ventricular myocardium.