Question

multiple choice question
the movement of ______ is responsible for the depolarization phase of the action potential in cardiac muscle cells.
o k+
o li+
o na+

Explanation:

In cardiac muscle cells, the influx of sodium ions ($Na^+$) causes the membrane potential to become less negative, leading to depolarization. Potassium ions ($K^+$) are mainly involved in repolarization, and lithium ions ($Li^+$) are not the main ions responsible for the depolarization phase of cardiac - muscle - cell action potential.

Answer:

O Na+