Question

what action is most responsible for the resting membrane potential in cardiac muscle cells? multiple choice movement of k+ through voltage - gated k+ channels movement of na+ through open na+ channels movement of ca2+ through voltage - gated ca2+ channels. closing of na+ and k+ voltage - gated channels

Explanation:

The resting membrane potential in cardiac - muscle cells is mainly due to the movement of potassium ions ($K^+$) through leak channels (a type of non - voltage - gated $K^+$ channels). But among the given options, the movement of $K^+$ through voltage - gated $K^+$ channels is related to maintaining the resting state compared to the other ion movements which are more involved in action potential generation. Sodium ($Na^+$) movement through open $Na^+$ channels is associated with depolarization, calcium ($Ca^{2 + }$) movement through voltage - gated $Ca^{2+}$ channels is related to the plateau phase of the cardiac action potential, and closing of $Na^+$ and $K^+$ voltage - gated channels is not the main factor for the resting membrane potential.

Answer:

Movement of $K^+$ through voltage - gated $K^+$ channels