Heart Physiology Practice Exam 2026 - Free Heart Physiology Practice Questions and Study Guide

Excessive potassium levels in the blood, a condition known as hyperkalemia, can significantly affect the process of depolarization in cardiac and neuronal cells. Depolarization is the critical change in membrane potential that occurs when sodium ions rush into the cells, making the inside more positively charged and allowing for the transmission of electrical impulses.

When potassium levels are too high, it alters the resting membrane potential of cardiac cells. Normally, potassium is involved in repolarization, where it exits the cell after an action potential. However, high levels of extracellular potassium can lead to a decrease in the driving force for potassium to leave the cell, causing the membrane potential to become less negative (more depolarized). This effect can disrupt the normal rhythm of the heart, potentially leading to arrhythmias or even cardiac arrest.

Understanding this physiological impact highlights the role of potassium in maintaining the electrical stability of the heart and the importance of regulating its levels within the narrow range that is necessary for normal cardiac function.