CVS Practice Test 2025 - Free CVS Practice Questions and Study Guide

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Question: 1 / 400

Which ions are involved during phase 3 of the pacemaker action potential?

Calcium influx

Sodium efflux

Potassium efflux

During phase 3 of the pacemaker action potential, the primary event is the efflux of potassium ions from the cardiac cells. This phase is characterized by repolarization, which occurs as potassium channels open and allow K+ ions to flow out of the cell. This outflow of positive charge helps to restore the negative membrane potential after the depolarization phase, which is primarily driven by calcium influx.

Understanding this phase is crucial for comprehending how pacemaker cells in the heart regulate their rhythm. The movement of potassium is essential for returning the membrane potential to its resting state, thus preparing the pacemaker cells for the next action potential. This cellular mechanism ensures that the heart beats in a coordinated manner, highlighting the importance of potassium in cardiac physiology.

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Chloride influx

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