The SA node as the cardiac pacemaker
Which structure normally sets the heart rate?
Answer A: explanation for every choice
A
Correct. The SA node depolarizes fastest, so it sets the rhythm.
B
The AV node delays conduction so the ventricles can fill.
C
The bundle of His carries the impulse from the AV node into the ventricles.
D
Purkinje fibers spread the impulse rapidly through the ventricular walls.
TakeawaySA node → AV node (delay) → bundle of His → Purkinje fibers.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb93.