Which of the following ions is primarily responsible for the outflow during cardiac depolarization?

During cardiac depolarization, the primary ion responsible for the outflow is potassium (K+). In the cardiac action potential, after the initial rapid depolarization phase caused mainly by the influx of sodium ions (Na+), there is a rapid repolarization phase where potassium channels open. This allows potassium to flow out of the cardiac cells, helping to restore the negative resting membrane potential and bring the cell back to its resting state.

The role of potassium outflow is crucial as it facilitates the resetting of the cardiac action potential, thereby allowing the heart muscle cells to prepare for the next cycle of depolarization. This repolarization process is essential for maintaining a regular heart rhythm and preventing arrhythmias. Understanding the significance of potassium's role in cardiac function is fundamental in the study of veterinary pharmacology as it relates to the cardiovascular system in animals.