Where is the sinoatrial node located?

• A. Wall of the right atrium
• B. Interventricular septum
• C. Posterior wall of left atrium
• D. Ventricular septum

Answer: (A)

The sinoatrial node sits in the wall of the right atrium near where the superior vena cava enters. This location lets it spontaneously generate rhythmic impulses—the heart’s natural pacemaker—and start the heartbeat. From there, the impulse spreads through the atria and then to the atrioventricular node to coordinate the timing of ventricular contraction.

The other locations aren’t correct because they pertain to different parts of the heart’s conduction system. The interventricular septum is the wall between the ventricles and houses parts of the pathway that carry impulses to the ventricles, not the pacemaker. The posterior wall of the left atrium and the ventricular septum are not where the initiating pacemaker sits.