CVS Practice Test 2026 – Complete Exam Preparation

Question: 1 / 400

Which ion influx occurs during phase 2 of the non-pacemaker action potential?

Potassium

Sodium

Calcium

During phase 2 of the non-pacemaker action potential, calcium ion influx is critically important. This phase, often referred to as the plateau phase, is characterized by the opening of voltage-gated calcium channels. This influx of calcium is what contributes to the prolonged depolarization and maintains the muscle contraction in cardiac cells.

The presence of calcium during this phase prevents repolarization from occurring too early, allowing for a coordinated and effective contraction of the heart muscle. This phase is essential for ensuring that the heart has enough time to pump blood effectively before the repolarization occurs, which is vital for maintaining proper cardiac function. The influx of calcium is a key factor in this regulatory mechanism, distinguishing it from the other ion movements that occur at different phases of the action potential.

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Chloride

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