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:

The increase in intracellular sodium induces the release of Ca⁺⁺ from the sarcoplasmic reticulum.
Calcium entry from the extracellular space through the voltage dependent Ca⁺⁺ channels.
The entry of extracellular Ca⁺⁺ causes the release of more Ca⁺⁺ ions by the sarcoplasmic reticulum, further increasing its intracellular concentration.

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 https://brainly.com/question/4473795