The rapid depolarization phase of the action potentials of myocardial contractile cells is due to which ion(s)? The rapid depolarization phase of the action potentials of myocardial contractile cells is due to which ion(s)? Na+ only Ca2+ only K+ only both Ca2+ and K+ both Na+ and K+

Na+ only

Explanation:

Depolarisation of membrane refers to the change in the resting membrane potential of the membrane of a cell which is usually -70mv to a more positive value.

This value changes when the positive ions move inside the cell which increases the positive charge inside the cell.

In the myocardial cell, the sodium ions move inside the cell which changes the potential towards the more positive side as a result of which the signals for contraction arises.

Thus, Na+ only is correct.

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