Definition of Blood Pressure

Blood Pressure – the force blood exerts against the walls of the arteries as it travels through them, as a combination of resistance and the heart’s pumping effort.

A sphygmomanometer is the device that measures blood pressure, reported in millimeters of mercury (mm Hg). A typical blood pressure reading reports the pressure at the peak (systole, at ventricular contraction) and trough (diastole, at ventricular filling) of the cardiac cycle. The first number in a blood pressure reading is the systolic measure and the second number is the diastolic measure. These measures are independently important as well as significant in combination. Blood pressure is among the vital signs health-care providers measure to assess general health status.

Several mechanisms within the body, including neurologic actions in the brainstem and hormonal actions initiated in the kidneys, regulate blood pressure. Clusters of specialized nerve cells in the heart and major arteries, called baroreflex sensors, continuously send biochemical signals to the regulatory mechanisms. These mechanisms are redundant that is, they overlap one another to respond to physiologic changes such as fluid volume and oxygen demand.

These mechanisms increase blood pressure by constricting arteries and arterioles, raising the resistance blood encounters as it flows through these blood vessels, and correspondingly increasing the rate and force of the heart’s contractions. They decrease blood pressure through reverse actions, dilating arteries and arterioles and decreasing the heart’s pumping force.

Blood pressure typically increases with exercise or stress, reflecting increased metabolism. Higher blood pressure pushes oxygen and nutrients more rapidly into the capillary beds, speeding the rate at which these substances reach cells.

Blood Pressure – Hypertension and Hypotension

Higher blood pressure than is optimal for cardiovascular health is hypertension; blood pressure that is too low to adequately circulate blood is hypotension. Most hypotension occurs as a side effect of medications or neurologic conditions, although some degree of hypotension is common with cardiovascular slowing in aging.

Researchers believe age-related hypotension reflects disturbances of the baroreflexes. Cardiologists may prescribe medications to constrict the arteries and intensify the heart’s contractions when hypotension causes symptoms such as mental confusion or syncope (fainting).

BLOOD PRESSURE VALUES
ClassificationSystolicDiastolic
healthy below120 mm Hg below80 mm Hg
prehypertension120–139 mm Hg80–89 mm Hg
stage 1 hypertension140–159 mm Hg90–99 mm Hg
stage 2 hypertension160 mm Hg and above100 mm Hg and above

Hypertension poses a significant threat to cardiovascular health, raising the risk for heart attack, renal failure, and stroke. Researchers do not fully understand how hypertension develops, though they do know the contributing factors the development of it (salt intake, physical inactivity, obesity, and diabetes) as well as how to influence blood pressure regulatory mechanisms to bring it under control in most situations. Hypertension exists when either systolic or diastolic pressure is elevated. Health conditions that contribute to hypertension include

  • Arteriosclerosis, atherosclerotic disease, and cigarette smoking, each of which stiffens the arteries and narrows the arterioles
  • Diabetes, which damages the blood vessels, particularly the smaller arteries and the arterioles
  • Obesity, which increases body mass and creates additional pressure against the blood vessels

Health experts recommend reduced salt consumption, weight loss and weight management, daily physical exercise, and no smoking to maintain optimal blood pressure. Many people who have hypertension also are on aspirin therapy or anticoagulation therapy to reduce their risk for heart attack and stroke.

See also ARTERY; EXERCISE AND HEALTH; LIFESTYLE AND CARDIOVASCULAR HEALTH.

Blood Pressure – Low / High – Normal / Systolis / Diastolic
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