What is the intrinsic rate of the SA node?

The intrinsic rate of the sinoatrial (SA) node is typically recognized as 60-100 beats per minute (bpm). The SA node is essential in controlling the heart's rhythm, acting as the primary pacemaker of the heart. Its firing rate directly influences how quickly the heart beats and can be affected by various factors, including autonomic nervous system input.

An intrinsic rate of 60-100 bpm indicates that under normal physiological conditions, the SA node generates electrical impulses at this frequency, which allows the heart to maintain an adequate heart rate during rest or moderate activity. This range is important for maintaining cardiovascular health, as it supports effective circulation and proper oxygen delivery throughout the body.

The other choices indicate different rates, which do not accurately represent the intrinsic firing rate of the SA node. A rate of 40-60 bpm suggests a slower rhythm, often seen in other types of pacemakers, such as the atrioventricular (AV) node, rather than the primary pacemaker. The higher rates of 100-120 bpm and 80-120 bpm exceed the typical intrinsic firing rate of the SA node, as while the SA node can be influenced to fire at increased rates due to factors like physical activity or stress, its intrinsic