Anatomy & PhysiologyPregunta 65 de 100
A patient's SA node fails completely. Which structure normally takes over, and at what rate?
a.The Purkinje fibers at 60 to 100 beats per minute
b.The AV junction at 40 to 60 beats per minute
c.The bundle branches at 100 to 120 beats per minute
d.The atrial muscle at 20 to 40 beats per minute
Explicación
The AV junction is the secondary pacemaker and assumes control at 40 to 60 beats per minute when the SA node fails, producing a junctional escape rhythm with absent or inverted P waves. The Purkinje network fires only at 20 to 40 and takes over if the junction also fails. Bundle branches conduct rather than pace at a fast rate, and general atrial muscle is not a designated escape pacemaker.
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