Biology » Biology 105: Animal Systems » Cardiovascular Diseases


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As previously mentioned blood pressure is the pressure exerted by the blood against the walls of the blood vessels, especially the arteries. Normal blood pressure at rest is within the range of \(\text{100}\)–\(\text{140}\) \(\text{mm Hg}\) systolic (top reading) and \(\text{60}\)–\(\text{90}\) \(\text{mm Hg}\) (bottom reading). High blood pressure (hypertension) is said to be present if it is persistently at or above \(\text{140}\)/\(\text{90}\) \(\text{mm Hg}\). Hypertension is a major risk factor for strokes, heart attacks and bursting of blood vessels (aneurysms). Hypertension is essentially caused by a resistance to blood flow in blood vessels.


The instrument used to measure blood pressure is a sphygmomanometer. This figure shows an automated arm blood pressure meter showing arterial hypertension. From the top reading systolic pressure is \(\text{158}\) \(\text{mm Hg}\) and diastolic reading is \(\text{99}\) \(\text{mm Hg}\) and the heart rate is \(\text{80}\) beats per minute.

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