The action potential of cardiac pacemaker cells is caused by A)inward diffusion of Na⁺. B)inward diffusion of Ca²⁺. C)inward diffusion of K⁺. D)outward diffusion of K⁺.

Question

Quizplus · Accepted Answer

The action potential in cardiac pacemaker cells is initiated by the inward diffusion of calcium ions (Ca²⁺) through funny channels (HCN channels). These channels open when the membrane potential is hyperpolarized, allowing the influx of calcium ions and causing depolarization of the cell. In contrast, the action potential in typical neurons and skeletal muscle cells is initiated by the inward diffusion of sodium ions (Na⁺) through voltage-gated sodium channels.

The Action Potential of Cardiac Pacemaker Cells Is Caused by