The rapid depolarization phase of the action potentials of myocardial contractile cells is due to Na⁺ ion.
The depolarization is caused when Na⁺ ions rapidly enters into neuron through open sodium channels. Sodium ions plays important role in various physiological process such as regulating blood volume, ph regulation, maintaining blood pressure, energy metabolism,osmotic equilibrium, excitation-contraction coupling, maintenance of cellular homeostasis, development and growth.
