New York State Emergency Medical Technician (EMT) Practice Exam

During what phase does the heart fill with blood?

1. Diastole

2. Systole

3. Repolarization

4. Depolarization

The correct answer is: Diastole

The phase during which the heart fills with blood is diastole. During this phase, the heart muscle relaxes after contraction, allowing the chambers of the heart—specifically the atria and ventricles—to expand and fill with blood from the circulation. The blood flows into the atria and then moves into the ventricles in preparation for the next contraction. In contrast, systole refers to the phase of the cardiac cycle when the heart contracts, pumping blood out of the chambers and into the arteries. This is when the heart is actively ejecting blood, which is distinct from the filling process. Repolarization and depolarization are terms associated with the electrical activity of the heart, referring to the recovery and activation of heart muscle cells, respectively. These processes coordinate the timing of the heart's contractions and are critical for ensuring that the heart beats in a synchronized manner. However, they are not phases associated with the physical filling of the heart with blood. Understanding the distinction between these phases is essential for comprehending how the heart works and ensures effective circulation throughout the body.