Blood pressure is the force of the blood pushing against the walls of the arteries. Each time the heart beats (about 60-70 times a minute at rest), it pumps out blood into the arteries. The up and down fluctuation of the arterial pressure results from the pulsatile nature of the cardiac output , i.e. The pulse pressure is determined by the interaction of the stroke volume of the heart, compliance (ability to expand) of the aorta , and the resistance to flow in the arterial tree. The second number is the pressure in the arteries when the heart relaxes between contractions. This is the diastolic pressure.

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Diastolic Pressure and your health

It is the diastolic blood pressure (bottom number) that causes concern when it goes over 90 because it measures the pressure created against the arterial walls when the heart is resting. You don't want a lot of pressure against your arteries constantly as that can cause them to balloon out (aneurysm). Blood is carried from the heart to all parts of your body in vessels called arteries. Blood pressure is the force of the blood pushing against the walls of the arteries. A garden hose might endure the wear and tear, but your arteries can become extremely damaged by such constant pressure—so damaged that the end result might include a heart attack, stroke (a brain attack), or kidney disease.

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Blood in the arteries

The blood then enters small vessels with muscular walls, called arterioles. The tone in the muscular walls of the arterioles determines how relaxed or constricted they are. As the cuff becomes filled with air, the pressure in the cuff increases, eventually cutting off the flow of blood through the arteries in the arm. The health care provider slowly lets air leak out of the blood pressure cuff, causing the pressure in the cuff to gradually decrease. Arteries narrow, and blood pressure goes up because it is more difficult for blood to circulate.

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