What is blood pressure, and how does it relate to hypertension?
Blood pressure is the force of the blood pushing against the artery walls. The force is generated with each heartbeat as blood is pumped from the heart into the blood vessels. The size and elasticity of the artery walls also affect blood pressure; each time the heart beats, pressure is created inside the arteries. When your blood pressure is high, it causes hypertension.
When blood is pumped out of the heart into the arteries, the pressure is at its greatest. The pressure falls in the arteries when the heart relaxes between beats. Two numbers are recorded when measuring blood pressure:
- Systolic pressure, the top number, refers to the pressure inside the artery when the heart contracts and pumps blood through the body.
- Diastolic pressure, the bottom number, refers to the pressure inside the artery when the heart is at rest and is filling with blood.
Both systolic and diastolic pressures are recorded as "mm Hg" (millimeters of mercury), representing how high the mercury column in the blood pressure cuff is raised by the pressure of the blood.