Which of the following minerals assists in regulating the heartbeat?

Potassium plays a crucial role in regulating the heartbeat due to its importance in maintaining proper electrical activity in heart cells. It is essential for the generation and transmission of electrical impulses that coordinate heartbeats. When potassium levels are optimal, they help ensure that muscles, including the heart, can contract and relax appropriately. This mineral influences the resting membrane potential and action potentials of cardiac cells, which are critical for normal heart rhythm.

While calcium is also important for heart function, particularly in muscle contraction and the mechanism of the heartbeat, potassium is more directly involved in regulating the electrical impulses that trigger the heartbeat itself. Therefore, potassium is recognized for its specific role in this regulatory function, making it the correct choice for this question.