What happens during systole in relation to blood pressure?

During systole, the ventricles of the heart contract, leading to the pumping of blood out of the heart into the arteries. This contraction increases the pressure in the ventricles, which forces blood into the systemic circulation (from the left ventricle) and pulmonary circulation (from the right ventricle). As a result, blood pressure rises during this phase, marking the peak of the cardiac cycle.

In contrast, during diastole, the heart relaxes, and blood flows into the chambers, which is not what occurs during systole. The expansion of blood vessels can occur due to various factors but is not directly a part of the heart's contraction phase. Similarly, the contraction of the atrial chambers occurs earlier in the cycle, during atrial systole, which sets up the filling of the ventricles, but is distinct from the events of ventricular contraction that characterize systole.