Effect of blood pressure

The causes of high blood pressure vary. Causes may include narrowing of the arteries, a greater than normal volume of blood, or the heart beating faster or more forcefully than it should. Any of these conditions will cause increased pressure against the artery walls. High blood pressure might also be caused by another medical problem. Most of the time, the cause is not known. Although high blood pressure usually cannot be cured, in most cases it can be prevented and controlled.

Effects of high blood pressure

Blood pressure exceeding normal values is called arterial hypertension. It itself is only rarely an acute problem; see hypertensive crisis. But because of its long-term indirect effects (and also as an indicator of other problems) it is a serious worry to physicians diagnosing it.

All level of blood pressure puts mechanical stress on the arterial walls. Higher pressures increase heart workload and progression of unhealthy tissue growth (atheroma) that develops within the walls of arteries. The higher the pressure, the more stress that is present and the more atheroma tend to progress and the heart muscle tends to thicken, enlarge and become weaker over time.

Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure, arterial aneurysms, and is the second leading cause of chonic renal failure after diabetes mellitus.

In the past, most attention was paid to diastolic pressure; but nowadays it is recognised that both high systolic pressure and high pulse pressure (the numerical difference between systolic and diastolic pressures) are also risk factors. In some cases, it appears that a decrease in excessive diastolic pressure can actually increase risk, due probably to the increased difference between systolic and diastolic pressures (see the article on pulse pressure).

Effects of low blood pressure

Blood pressure that is too low is known as hypotension. The similarity in pronunciation with hypertension can cause confusion.

Low blood pressure may be a sign of severe disease and requires more urgent medical attention.

When blood pressure and blood flow decrease beyond a certain point, the perfusion of the brain becomes critically decreased (i.e., the blood supply is not sufficient), causing lightheadedness, dizziness, weakness and fainting.

However, people who function well while maintaining low blood pressures have lower rates of cardiovascular disease events than people with normal blood pressures.

Source http://en.wikipedia.org/ & http://www.nhlbi.nih.gov