Diastolic Filling (Bottom of Loop): As the ventricle relaxes, it fills with blood from the atrium. The volume increases, but the pressure remains relatively low.
Isovolumetric Contraction (Vertical Line Upwards): After the atrioventricular valve closes and before the aortic valve opens, the ventricle contracts without ejecting any blood (volume stays constant). The pressure rises steeply during this phase.
Ejection Phase (Sloping Line Upwards to the Right): The aortic valve opens, and blood is ejected into the aorta. The volume decreases as blood is pumped out, and the pressure remains high but may decrease somewhat toward the end of ejection.
Isovolumetric Relaxation (Vertical Line Downwards): After ejection, the aortic valve closes, but the atrioventricular valve has not yet opened. The ventricle relaxes, and the pressure drops rapidly while the volume remains constant.
Return to Diastolic Filling (Closing the Loop): The atrioventricular valve opens again, and the cycle repeats.