The rhythmic expansion and contraction of the heart is called.

Explanation:

The cardiac cycle is the heart's rhythmic contraction and relaxation.

The contraction of the heart is known as cardiac systole, and the relaxation is known as cardiac diastole. The cardiac cycle encompasses both contraction and relaxation.

The heart beats 72 times per minute, which translates to 72 cardiac cycles per minute.

Cardiac cycle refers to the heart's cyclic expansion and contraction.

Final Answer:

Cardiac cycle.