What happens during systole?

During systole, the heart is actively contracting. This is the phase of the cardiac cycle when the heart muscles contract to pump blood out of the heart. Specifically, during this phase, the ventricles contract, pushing blood into the pulmonary artery and aorta. This contraction is crucial for maintaining blood circulation throughout the body, ensuring that oxygen-rich blood reaches various organs and tissues while also returning deoxygenated blood to the lungs for oxygenation.

Understanding this process is essential, as it sets the foundation for how the heart functions during the entire cardiac cycle. In contrast, the other options describe different phases or aspects of heart function. The heart relaxing and filling with blood occurs during diastole, which follows systole. The heart being at rest between beats refers to the periods of the cardiac cycle but does not specifically address systole. Lastly, the assertion regarding a significant decrease in heart rate is unrelated to the contraction phase and does not accurately describe what occurs during systole.