Hypertension
Hypertension or High Blood Pressure, medical condition in which constricted arterial blood vessels increase the resistance to blood flow, causing an increase in blood pressure against vessel walls. The heart must work harder to pump blood through the narrowed arteries. If the condition persists, damage to the heart and blood vessels is likely, increasing the risk for stroke, heart attack, and kidney or heart failure. Often called the “silent killer,” hypertension usually causes no symptoms until it reaches a life-threatening stage.
Physicians use two measurements to describe blood pressure. Systolic pressure measures blood pressure as the heart contracts to pump out blood. Diastolic pressure measures blood pressure as the heart relaxes to allow blood to flow into the heart. An instrument called a sphygmomanometer measures systolic and diastolic pressure using units of millimeters of mercury (abbreviated mm Hg).
Blood pressure is classified in four categories: normal, prehypertension, stage 1 hypertension, and stage 2 hypertension. Normal blood pressure in an adult is less than 120/80 mm Hg, in which 120 describes systolic pressure and 80 describes diastolic pressure. Prehypertension is defined as a systolic pressure of 120 to 139 mm Hg or a diastolic pressure of 80 to 89 mm Hg. People with prehypertension are likely to develop hypertension at some point during their life. Stage 1 hypertension is defined as a systolic pressure of 140 to 159 mm Hg or a diastolic pressure of 90 to 99 mm Hg. Stage 2 hypertension is defined as 160/100 mm Hg or higher.
HOW HYPERTENSION DEVELOPS
Two factors determine blood pressure: the amount of blood the heart pumps and the diameter of the arteries receiving blood from the heart. When the arteries narrow, they increase the resistance to blood flow. The heart works harder to pump more blood to make sure the same amount of blood circulates to all the body tissues. The more blood the heart pumps and the smaller the arteries, the higher the blood pressure.
The kidneys play a major role in the regulation of blood pressure. Kidneys secrete the hormone renin, which causes arteries to contract, thereby raising blood pressure. The kidneys also control the fluid volume of blood, either by retaining salt or excreting salt into urine. When kidneys retain salt in the bloodstream, the salt attracts water, increasing the fluid volume of blood. As a higher volume of blood passes through arteries, it increases blood pressure.
Physicians use two measurements to describe blood pressure. Systolic pressure measures blood pressure as the heart contracts to pump out blood. Diastolic pressure measures blood pressure as the heart relaxes to allow blood to flow into the heart. An instrument called a sphygmomanometer measures systolic and diastolic pressure using units of millimeters of mercury (abbreviated mm Hg).
Blood pressure is classified in four categories: normal, prehypertension, stage 1 hypertension, and stage 2 hypertension. Normal blood pressure in an adult is less than 120/80 mm Hg, in which 120 describes systolic pressure and 80 describes diastolic pressure. Prehypertension is defined as a systolic pressure of 120 to 139 mm Hg or a diastolic pressure of 80 to 89 mm Hg. People with prehypertension are likely to develop hypertension at some point during their life. Stage 1 hypertension is defined as a systolic pressure of 140 to 159 mm Hg or a diastolic pressure of 90 to 99 mm Hg. Stage 2 hypertension is defined as 160/100 mm Hg or higher.
HOW HYPERTENSION DEVELOPS
Two factors determine blood pressure: the amount of blood the heart pumps and the diameter of the arteries receiving blood from the heart. When the arteries narrow, they increase the resistance to blood flow. The heart works harder to pump more blood to make sure the same amount of blood circulates to all the body tissues. The more blood the heart pumps and the smaller the arteries, the higher the blood pressure.
The kidneys play a major role in the regulation of blood pressure. Kidneys secrete the hormone renin, which causes arteries to contract, thereby raising blood pressure. The kidneys also control the fluid volume of blood, either by retaining salt or excreting salt into urine. When kidneys retain salt in the bloodstream, the salt attracts water, increasing the fluid volume of blood. As a higher volume of blood passes through arteries, it increases blood pressure.
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