Hypertension is defined as the elevation in overall blood pressure. Blood pressure is the amount of force exerted on the walls of the arteries by the heart in its effort to pump blood through the body. Blood pressure is measured in two numbers. The first, or top number is the "systolic" pressure, created when the heart contracts. The second, or bottom number is the "diastolic" pressure, or the period during which the heart relaxes.
An example of a normal blood pressure is 120/80. The higher the systolic or diastolic blood pressure, the greater chance of sustaining cardiac damage or illness. It should be understood that the higher the blood pressure level, even when within the normal range, the greater one's risk may be for heart attack or stroke. For example, a person with a blood pressure reading of 100/70 would be at a somewhat lower risk for heart attack or stroke than would a person whose blood pressure is 120/80, although both blood pressures would be considered within normal limits.