What is the role of potassium in Phase 4 of the action potential in the heart?

In Phase 4 of the action potential in the heart, the primary role of potassium is associated with its movement out of the cell. This phase is known as the resting phase or the recovery phase, where the cell prepares for the next action potential. During this phase, potassium ions exit the cardiac myocyte through potassium channels, which helps to restore the membrane potential towards a stable resting phase following depolarization and repolarization events.

The outward movement of potassium ions is essential for maintaining the negative charge inside the cell relative to the outside, allowing the cell to return to its resting state. This action contributes to the establishment of a stable resting potential, which is crucial for the heart's ability to fire action potentials in a rhythmic and coordinated manner.

While calcium entry and potassium moving into the cell are processes that happen at other phases of the action potential, they do not pertain to Phase 4. Therefore, the correct answer relates directly to the significant role of potassium as it exits the cardiac cell to help achieve the resting membrane potential.