What is the primary characteristic of phase 2 of the action potential?

Phase 2 of the action potential, often referred to as the plateau phase, is characterized by a prolonged depolarization during which the membrane potential remains relatively stable. This phase is essential in cardiac myocytes because it allows for a sustained contraction of the heart muscle, which is crucial for effective pumping of blood. During this phase, calcium ions enter the cell while potassium ions exit, balancing out the charges and creating the plateau effect.

The plateau phase ensures that there is a longer refractory period, preventing premature electrical impulses from triggering additional contractions and maintaining the heart's rhythm. This is vital for heart function, as it prevents conditions like arrhythmias, which can arise if the heart muscle is not allowed adequate time to relax between beats. Thus, the primary characteristic of phase 2 of the action potential is its unique plateau that results in a temporary stabilization of membrane potential, distinguishing it from other phases such as repolarization and rapid depolarization, which occur at different stages of the action potential cycle.