Which ions are involved in the depolarization of cardiac cells?

The depolarization of cardiac cells primarily involves sodium and calcium ions. When a cardiac cell is stimulated, sodium channels open, allowing sodium ions to flow into the cell. This influx of sodium ions results in a rapid change in the membrane potential, leading to depolarization.

Calcium ions also play a significant role during this process. Calcium influx through specific channels not only contributes to further depolarization but is also vital for the contraction of the cardiac muscle. In contrast, potassium ions are responsible for repolarization after the depolarization phase; during depolarization itself, their movement is not what drives the initial change in membrane potential.

Thus, the correct involvement of sodium and calcium ions during the depolarization phase of cardiac action potential underlies the selected answer, highlighting the critical roles these ions play in the electrical activity of the heart.