BLOOD PRESSURE This lesson meets the following DoE Specific Curriculum Outcomes for Biology 11: and 317-1

BLOOD PRESSURE Blood moves through arteries is under pressure. Because the walls of the arteries are elastic in nature, they stretch and expand under increased blood pressure.

BLOOD PRESSURE A pulse is the alternate expansion (high pressure) and contraction (low pressure) that can be felt in an artery each time the left ventricle contracts and relaxes. Physicians measure arterial blood pressure with an instrument called a SPHYGMOMANOMETER or blood pressure cup.

Sphygmomanometer

BLOOD PRESSURE Blood pressure is measured in terms of a column of mercury in a tube in the instrument. During systole (in an average adult), the pressure is enough to raise the column of mercury 120 millimetres high. During diastole, the mercury will drop to around 80 mm.

BLOOD PRESSURE Blood pressure is commonly stated in the form of systole/diastole. For the average adult, this would be 120/80. During exercise and times of stress, blood pressure will rise. High blood pressure or HYPERTENSION results when the blood pressure remains high through the heartbeat cycle.

The Silent Killer Figure 17. Atlantic health districts with a notably higher percentage of the population aged 12 and over with high blood pressure, for both genders, compared to Canada, 2000/01, (%)

BLOOD PRESSURE Normal blood pressure readings range from 120 to 140 systolic and 80 to 90 diastolic. Systolic reading of 140 to 160 and diastolic readings of 90 to 95 are considered borderline. Blood pressure exceeding 160 over 95 is considered hypertension.

BLOOD PRESSURE A common cause of high blood pressure is “hardening of the arteries” which results from deposits of cholesterol and other fatty materials on the inner walls of the arteries. This causes a loss of elasticity and a decrease in the diameter of the arteries resulting in increased blood pressure. Unchecked, it can lead to stroke or heart attack.

Hypertension »SymptomsSymptoms Categories for Blood Pressure Levels in Adults (in mmHg, or millimeters of mercury) Category Systolic (top number) Diastolic (bottom number) Normal Less than 120 And Less than 80 Prehypertension120–139 Or 80–89 High blood pressure Stage 1140–159 Or 90–99 Stage 2160 or higher Or 100 or higher