What is the normal firing rate of the SA node?

The normal firing rate of the sinoatrial (SA) node is typically between 60 and 100 beats per minute (bpm). The SA node is considered the natural pacemaker of the heart, and it establishes the rhythm for the heart's contraction by generating electrical impulses that stimulate the heart muscles. This firing rate supports a healthy cardiovascular function, allowing adequate cardiac output for the body's demands at rest and during activity.

The heart's ability to maintain an optimal rhythm is crucial, as deviations from this normal range can lead to various types of arrhythmias or cardiac dysfunctions. The other ranges provided in the choices reflect the firing rates of different parts of the conduction system. For example, the atrioventricular (AV) node has a firing rate of about 40-60 bpm, and the bundle branches and Purkinje fibers fire more slowly, at 20-40 bpm. Knowing the normal functioning rate of the SA node helps paramedics and other healthcare professionals assess and interpret cardiac rhythms effectively.