What is the firing rate of the atrioventricular (AV) node?

The firing rate of the atrioventricular (AV) node is indeed typically in the range of 40-60 beats per minute (bpm). This range reflects the intrinsic pacing ability of the AV node, which serves as a critical relay point in the heart's electrical conduction system. While the sinoatrial (SA) node acts as the primary pacemaker with a higher firing rate of 60-100 bpm, the AV node acts as a backup and ensures that impulses are properly conducted from the atria to the ventricles, maintaining coordinated heart function.

In the context of other choices, rates such as 20-40 bpm are characteristic of the Purkinje fibers or other ectopic pacemakers when they take over in the absence of more dominant pacemakers, while the 60-100 bpm range corresponds to the SA node. The rate of 60-80 bpm does not reflect the AV node's capabilities accurately, as it slightly exceeds the established range for this structure. Thus, the choice of 40-60 bpm aligns with the established physiological understanding of the AV node's firing rate.