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 blood is forced into the arteries which expand to receive blood. These arteries have a muscular lining which resists this pressure. Thus 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 upon the strength of the heart muscle, the amount of blood in the circulatory system and the condition of the arteries.
There are two kinds of pressures – systolic and diastolic. Systolic is the maximum pressure that occurs when the left ventricle contracts. Diastolic is the minimum pressure that occurs just before the heartbeat which follows.
When a doctor measures 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 if it exceeds the figure of 100 plus his age or if the diastolic pressure exceeds 100. High blood pressure can cause heart failure, apoplexy, or kidney diseases. It may also burst a blood vessel in the eye or the brain, thus causing blindness or a hemorrhage. Symptoms of high blood pressure are headaches, hot flashes and anger.
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 pressure falls considerably, the oxygen supply to the brain and other parts also gets reduced. This can cause death. Physicians use drugs which contract the muscular walls of the blood vessels to raise the blood pressure.
Abnormal high blood pressure may be due to the constriction of arteries or due to damage to one or both kidneys. Excessive weight and lack of exercise can also contribute to hypertension. Temporary high blood pressure can be due to excitement or emotional stresses.
