Heart Cycle in Systole
There are two phases of the cardiac cycle: systole and diastole. Systole is the phase during which the heart contracts, pushing blood out of the left and right ventricles, into the systemic and pulmonary circulation respectively. The ventricles fill with more and more blood until the pressure is great enough against the semilunar valves that they open, allowing the blood to enter the aorta and pulmonary trunk. Systolic pressure is the blood pressure felt in your arteries when your heart beats. Blood pressure is denoted as a fraction, with the systolic pressure being the top number. Blood pressure higher than the average of 120/80 enters the range of hypertension.