The heart is a vital organ that pumps blood to different parts of the body. The outflow of the blood takes place when the heart's left ventricle contracts. Then the blood is forced into the arteries, which expand to receive the incoming blood. These arteries have a muscular lining, which resists this pressure. Thus, the blood is squeezed out of them into the smaller vessels of the body. By blood pressure, we mean the amount of pressure that blood exerts on the walls of the arteries. The amount of pressure depends on the heart muscle's strength, the amount of blood in the circulatory system and the condition of the arteries.

There are two kinds of pressures - maximum and minimum. The maximum pressure occurs when the left ventricle contracts. It is called systolic pressure. The minimum pressure occurs just before the heartbeat which follows. It is called the diastolic pressure. When a doctor measures the blood pressure, he uses an instrument in which a column of mercury rises or falls under the pressure. It is marked in millimeters. The average systolic pressure in a young man is about 120 mm of mercury and the diastolic pressure is about 80. These figures are usually stated as 120/80 or 120 over 80.

Blood pressure usually rises with age because the arteries become less flexible. Anxiety or exercise may also cause pressure to rise temporarily. It is also increased by a number of diseases. A person is said to have high blood pressure or hypertension of it exceeds the 100 plus his age or if his diastolic pressure is greater than 100. High blood pressure can cause heart failure, apoplexy, or kidney diseases. Abnormally low blood pressure occurs when a person has a heart attack or loses large amount of blood because of some injury etc. When the blood press falls considerably, the oxygen supply to the brain and other parts of the body also are reduced. This can result in serious complications including death. Physicians use drugs, which contract the muscular walls of the blood vessels to raise the blood pressure.

Abnormally high blood pressure may be due to the constriction of arteries. It may also be due to damage to one or both kidneys causing them to release more rennin. Excessive weight and lack of exercise can also contribute to hypertension. High blood pressure may cause heart failure. It may also burst a blood vessel in the eye or the brain and cause blindness or a hemorrhage.

When someone has high or low blood pressure, he or she should consult a good doctor and undergo proper treatment. High blood pressure has no cure but can be kept under control by regular monitoring. With modern technology, it is no longer needed to have a stethoscope and pump meter to display someone's blood pressure. Instead, electronic gadgets that can be attached to the forearm or even the wrist have appeared that accurately provide the reading to the patient without the help of another person. Such devices should be used regularly by a person diagnosed with high blood pressure to ensure a healthy living.

Michael Russell Your Independent guide to Blood Pressure