Blood pressure is the force exerted by circulating blood on the walls of blood vessels. Arteries are vessels that carry blood from the pumping heart to all the tissues and organs of the body. Blood pressure is generated by the heart pumping blood into the arteries and regulated by the response by the arteries to the flow of blood.
By convention, an individual's blood pressure is expressed as systolic/diastolic blood pressure, for example, 120/80.The systolic blood pressure (the top number) represents the pressure in the arteries as the muscle of the heart contracts and pumps blood into them. The diastolic blood pressure (the bottom number) represents the pressure in the arteries as the muscle of the heart relaxes after it contracts. Blood pressure always is higher when the heart is pumping than when it is relaxing.
Systolic blood pressure for most healthy adults falls between 90 and 120 millimeters of mercury (mm Hg). Normal diastolic blood pressure falls between 60 and 80 mm Hg. Current guidelines define normal blood pressure as lower than 120/80.
Low blood pressure (hypotension) is pressure that is so low that it causes symptoms or signs due to the low flow of blood through the arteries and veins. When the flow of blood is too low to deliver enough oxygen and nutrients to vital organs such as the brain, heart, and kidney, the organs do not function normally and may be permanently damaged.
Unlike high blood pressure, low blood pressure is defined primarily by signs and symptoms of low blood flow not by a specific blood pressure number. Some individuals may have a blood pressure of 90/50 with no symptoms of low blood pressure and therefore do not have low blood pressure. However, others who normally have high blood pressure may develop symptoms of low blood pressure if their blood pressure drops to 100/60.
The development of lightheadedness, dizziness, or fainting upon standing caused by low blood pressure is called orthostatic hypotension. Normal individuals are able to compensate rapidly for the low pressure created by standing. When there is insufficient blood pressure to deliver blood to the coronary arteries (the arteries that supply blood to the heart's muscle), a person can develop chest pain or even a heart attack. When insufficient blood is delivered to the kidneys, the kidneys fail to eliminate wastes from the body, for example, urea and creatinine, and an increase in their levels in the blood occur. Shock is a life–threatening condition where persistently low blood pressure causes organs such as kidney(s), liver, heart, lung, and brain to fail rapidly.
Blood pressures over 130/80 are considered high. High blood pressure (hbp) or hypertension means high pressure (tension) in the arteries. High blood pressure does not mean excessive emotional tension, although emotional tension and stress can temporarily increase blood pressure. Normal blood pressure is below 120/80; blood pressure between 120/80 and 139/89 is called "pre–hypertension", and a blood pressure of 140/90 or above is considered high.
High blood pressure increases the risk of developing heart disease, kidney disease, hardening of the arteries, eye damage and brain damage. The diagnosis of high blood pressure is important so efforts can be made to normalize blood pressure and prevent complications.
When the heart beats, it pumps blood to the blood vessels and creates pressure in them. If one is healthy, the blood vessels are muscular and elastic. They stretch when the heart pumps blood through them. The heart beats about 60 to 80 times a minute under normal conditions. The blood pressure rises with each heartbeat and falls when the heart relaxes between beats. The blood pressure can change from minute to minute, with changes in posture, exercise or sleeping, but it should normally be less than 130/80 mm Hg for an adult. Blood pressure says that anything above this level is high.
High blood pressure usually has no symptoms; in fact, many people have blood pressure for years without even knowing it. It doesn’t refer to being tense, nervous or hyperactive. You can be a calm, relaxed person and still have blood pressure. Uncontrolled high blood can lead to stroke, heartattack, congestive heart failure or kidney failure, all of which are fatal. This is why high blood pressure is often called the “silent killer”
Source: Portal Content Team