What is the function of sodium and potassium in cardiac action potentials?

Sodium and potassium play a vital role in the generation and propagation of cardiac action potentials, which are essential for the electrical activity of the heart. During the cardiac action potential, the influx of sodium ions into the cardiac cells leads to depolarization, causing the cell to become more positively charged. This rapid rise in voltage is crucial for initiating the contraction of heart muscle.

Subsequently, potassium ions are responsible for repolarization. As the cardiac cell returns to its resting state, potassium exits the cell, restoring the negative charge inside relative to the outside environment. This movement of potassium ions helps reset the membrane potential, allowing the heart muscle to relax and prepare for the next electrical impulse.

The interplay between sodium and potassium is fundamental to the cardiac cycle, ensuring that the heart beats in a coordinated manner. Understanding this process is essential for recognizing how disruptions in sodium or potassium levels can lead to arrhythmias or other cardiac conditions.