Smooth and Cardiac Muscle Physiology · Physiology

The plateau phase of the cardiac action potential is mainly due to:

  1. Rapid sodium influx
  2. Delayed potassium efflux
  3. Sustained calcium influx
  4. Chloride channel opening
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Correct answer: Sustained calcium influx

The plateau phase results from prolonged calcium entry through L-type calcium channels. This delays repolarization and prolongs contraction.

Difficulty: Medium Question 6 of 20

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