Blood Pressure

Blood pressure is like a hose pipe. It depends upon how much blood flows into a blood vessel and how easily it can flow out.

Pressure It is highest in the arteries because the blood pumps fast, but it can’t flow out through arterioles easily because they are narrow. It is lower in the capillaries because blood flows into them more slowly because the tubes are getting wider. It is lowest in the veins because the blood drains into them slowly and they are the widest vessels.

Measuring Blood Pressure It is always measured at an artery in your arm. The pressure in the artery rises when your heart contracts and falls when you relax. Both values are measured. Normal blood pressure is 120 mm when it contracts and 80 mm when it relaxes.

Measuring Blood Pressure The doctor pumps up the cuff until the pressure inside it just equals the pressure in the artery. He can tell when to stop by listening through the stethoscope. As the cuff is pumped up, the mercury rises in the tube. He then lets off the pressure until he hears a noise.

Blood Pressure and Exercise When you exercise your heart beats faster and pumps more blood. Your blood pressure rises. If it goes to high it is dangerous. Your body takes actions to do this automatically by the brain sending a message to the arterioles to open wider.