Diastolic pressure occurs near the beginning of the cardiac cycle. It is theminimum pressure in the arteries when the pumping chambers of the heart — ventricles — fill with blood. Near the end of the cardiac cycle, systolic pressure, or peak pressure, occurs when the ventricles contract.
As the heart beats, it pumps blood through a system of blood vessels, which carry blood to every part of the body. Blood pressure is the force that blood exerts on the walls of blood vessels. All or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the next is called a cardiac cycle. Problems in the cardiac cycle can cause low or high blood pressure.