The prolonged electrical depolarization of cardiac muscle cells that occurs during contraction is due primarily to the persistent influx of what ion?

The prolonged electrical depolarization of cardiac muscle cells -that occurs during contraction- is due primarily to the persistent influx of calcium ion

Explanation:

The action potential of the heart muscle is longer with respect to skeletal muscle (around 300 milliseconds), and this is due to the activity of calcium (Ca⁺⁺ ) in the intracellular compartment.

The initial depolarization of cardiac muscle fiber depends on the entry of sodium (Na⁺) into the cell. However, for the action potential to occur and be maintained, Ca⁺⁺  must increase its cytoplasmic levels, which depends on:

This is how the ion that guarantees the duration of the action potential of the cardiac muscle cell is the Ca⁺⁺.

Learn more:

Calcium, sodium and cardiac muscle cells link