What is the intrinsic firing rate of the SA node?

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Multiple Choice

What is the intrinsic firing rate of the SA node?

The intrinsic firing rate is the baseline pace that pacemaker cells would generate without autonomic influence. The SA node, as the primary pacemaker, has the fastest intrinsic rate among the conduction system, so it sets the heart rate when autonomic input is neutral. That intrinsic rate is about 60–100 beats per minute. In contrast, if the SA node doesn’t drive the heart, the AV node paces at roughly 40–60 bpm, and ventricular/purkinje tissue can pace at about 20–40 bpm. So 60–100 bpm best matches the SA node’s inherent rhythm, while the other ranges correspond to slower nodal or escape rhythms or to rates seen under autonomic modulation rather than intrinsic pacing.

The intrinsic firing rate is the baseline pace that pacemaker cells would generate without autonomic influence. The SA node, as the primary pacemaker, has the fastest intrinsic rate among the conduction system, so it sets the heart rate when autonomic input is neutral. That intrinsic rate is about 60–100 beats per minute. In contrast, if the SA node doesn’t drive the heart, the AV node paces at roughly 40–60 bpm, and ventricular/purkinje tissue can pace at about 20–40 bpm. So 60–100 bpm best matches the SA node’s inherent rhythm, while the other ranges correspond to slower nodal or escape rhythms or to rates seen under autonomic modulation rather than intrinsic pacing.

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