4. HOW DOES HYPERTENSION OCCUR?
Hypertension, also called high blood pressure, condition that arises when the blood pressure is abnormally high. Hypertension occurs when the body’s smaller blood vessels (the arterioles) narrow, causing the blood to exert excessive pressure against the vessel walls and forcing the heart to work harder to maintain the pressure.
Although the heart and blood vessels can tolerate increased blood pressure for months and even years, eventually the heart may enlarge (a condition called hypertrophy) and be weakened to the point of failure. Injury to blood vessels in the kidneys, brain, and eyes also may occur.
Blood pressure is actually a measure of two pressures, the systolic and the diastolic. The systolic pressure (the higher pressure and the first number recorded) is the force that blood exerts on the artery walls as the heart contracts to pump the blood to the peripheral organs and tissues.
The diastolic pressure (the lower pressure and the second number recorded) is residual pressure exerted on the arteries as the heart relaxes between beats. A diagnosis of hypertension is made when blood pressure reaches or exceeds 140/90 mmHg (read as “140 over 90 millimetres of mercury”).