Which node initiates the electrical impulse that sets the heart rate?

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Multiple Choice

Which node initiates the electrical impulse that sets the heart rate?

The heart’s pacing sits with automaticity in the sinoatrial node. This group of pacemaker cells fires spontaneously, generating an impulse at its intrinsic rate (about 60–100 beats per minute in a healthy adult). That impulse starts in the SA node and then travels through the atrioventricular node and onward via the Bundle of His and Purkinje fibers to coordinate the answer—atrial contraction followed by ventricular contraction—setting the overall heart rate. The atrioventricular node can take over if the SA node fails, but its intrinsic rate is slower (roughly 40–60 bpm), so it does not normally set the pace. The Bundle of His and Purkinje fibers are conduits for rapid conduction rather than initiators of the rhythm; they transmit impulses but don’t establish the rate under normal circumstances.

The heart’s pacing sits with automaticity in the sinoatrial node. This group of pacemaker cells fires spontaneously, generating an impulse at its intrinsic rate (about 60–100 beats per minute in a healthy adult). That impulse starts in the SA node and then travels through the atrioventricular node and onward via the Bundle of His and Purkinje fibers to coordinate the answer—atrial contraction followed by ventricular contraction—setting the overall heart rate.

The atrioventricular node can take over if the SA node fails, but its intrinsic rate is slower (roughly 40–60 bpm), so it does not normally set the pace. The Bundle of His and Purkinje fibers are conduits for rapid conduction rather than initiators of the rhythm; they transmit impulses but don’t establish the rate under normal circumstances.

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