Myocardial cells exhibit a plateau phase instead of quickly repolarizing.This is due to A)inward diffusion of calcium through slow Ca²⁺ channels. B)inward diffusion of sodium through fast Na⁺ channels. C)inward diffusion of potassium through voltage-gated K⁺ channels. D)outward pumping of sodium by the Na⁺/K⁺ pump.

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Quizplus · Accepted Answer

The plateau phase in myocardial cells is due to the inward diffusion of calcium through slow Ca²⁺ channels, which prolongs the depolarization phase and creates a stable membrane potential. This is different from other types of cells, which quickly repolarize due to outward diffusion of potassium ions. Sodium channels also play a role in the depolarization phase, but they quickly inactivate and do not contribute to the plateau phase. The Na⁺/K⁺ pump is involved in maintaining the resting membrane potential, but does not directly contribute to the plateau phase.

Myocardial Cells Exhibit a Plateau Phase Instead of Quickly Repolarizing