Arteries become damaged when high blood pressure is persistent.  It speeds up the deposits of cholesterol and other fatty materials that collect in the arteries resulting in atherosclerosis.  This may cause arteries to weaken and sometimes even bulge and rupture.  It can cause the heart to enlarge.  Sometimes, tissues (particularly in the brain, heart and kidneys) are damaged which frequently results in early death.  As blood pressure continues to rise the risk of stroke, heart attack, heart failure and kidney failure also increase.  On occasion, very high blood pressure will even impair vision.  Treatment effectively controls high blood pressure and may help prevent the problems it can potentially cause.  The measurement of an individual’s blood pressures consists of two numbers. The higher number (systolic pressure) represents the pressure when the heart beats.  The lower number is referred to as diastolic pressure, which actually refers to the pressure when the heart relaxes between beats.  Ideal blood pressure is usually considered to be 120/80 mm Hg (millimeters of mercury).  This reading is usually referred to as "120 over 80".  High blood pressure is when systolic pressure is 140 mm Hg. or higher, and when the diastolic pressure is 90 mm Hg. or higher.  When younger people have high blood pressure, both systolic and diastolic blood pressure is usually high.  Older people with high blood pressure, frequently have high systolic blood pressure (more than 140 mm Hg) while diastolic pressure remains in the normal range (less than 90 mm Hg.).  This disorder is usually referred to as isolated systolic hypertension and may actually have greater risk for harm than when both systolic and diastolic pressures are high. 

An individual’s blood pressure is at least partly determined by how well the heart, arteries and kidneys work together.  Drugs that are used to treat high blood pressure (antihypertensive drugs) lower blood pressure by affecting how these organs function.  The way the body controls and determines blood pressure is relatively complicated.  It involves the heart, arteries and kidneys working together. Blood pressure is affected by the following: 

• How fast the heart is beating and how forcefully it contracts.  An increase in the force or rate tends to increase blood pressure.

• Whether the small arteries that carry blood to the tissues can expand (dilate) and contract (constrict).  If the vessels have trouble dilating, are blocked or stiff, the heart must work harder to pump blood into them and blood pressure increases.

• Whether the kidneys can remove enough water and salt from the body.  If water and salt are not effectively removed from the body, the amount of blood in the body increases ((blood volume). When blood volume increases, the heart has to work harder causing blood pressure to increase.

Certain hormones in the nervous system also have an effect on blood pressure.  They help regulate the heart rate, the force of the heart’s contractions and the diameter of arteries.  Some hormones also affect the amount of water and salt that the kidneys are able to excrete resulting in high blood pressure.