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11.28: Blood Pressure

Difficulty Level: At Grade Created by: CK-12
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Why check your blood pressure?

It's a good idea to have a blood pressure test as part of a routine physical, especially in adulthood. High blood pressure is a risk factor for heart disease and stroke. It's important to know if you have high blood pressure, so it can be treated. A combination of medications and lifestyle changes can be successful in lowering your blood pressure.

Blood Pressure

The health of your whole body depends on the good health of your cardiovascular system. One measure of the health of your cardiovascular system is blood pressure. Blood pressure occurs when circulating blood puts pressure on the walls of blood vessels. Since blood pressure is primarily caused by the beating of your heart, the walls of the arteries move in a rhythmic fashion. Blood in arteries is under the greatest amount of pressure. The pressure of the circulating blood slowly decreases as blood moves from the arteries and into the smaller blood vessels. Blood in veins is not under much pressure.

Healthy Blood Pressure Ranges

Blood pressure is read as two numbers. The first number is the systolic pressure. The systolic pressure is the pressure on the blood vessels when the heart beats. This is the time when there is the highest pressure in the arteries. The diastolic pressure, which is the second number, is when your blood pressure is lowest, when the heart is resting between beats.

Healthy ranges for blood pressure are:

  • Systolic: less than 120
  • Diastolic: less than 80

Blood pressure is written as systolic/diastolic. For example, a reading of 120/80 is said as "one twenty over eighty." These measures of blood pressure can change with each heartbeat and over the course of the day. Pressure varies with exercise, emotions, sleep, stress, nutrition, drugs, or disease.

Studies have shown that people whose systolic pressure is around 115, rather than 120, have fewer health problems. Clinical trials have shown that people who have blood pressures at the low end of these ranges have much better long term cardiovascular health. Blood pressure is measured with a sphygmomanometer ( Figure below ).

A digital sphygmomanometer is made of an inflatable cuff and a pressure meter to measure blood pressure. This reading shows a blood pressure of 126/70.

Hypertension , which is also called "high blood pressure," occurs when a person’s blood pressure is always high. Hypertension is said to be present when a person's systolic blood pressure is always 140 or higher, and/or if the person's diastolic blood pressure is always 90 or higher. Having hypertension increases a person’s chance for developing heart disease, having a stroke, or suffering from other serious cardiovascular diseases. Hypertension often does not have any symptoms, so a person may not know that he or she has high blood pressure. For this reason, hypertension is often called the silent killer. Treatments for hypertension include diet changes, exercise, and medication. Foods thought to lower blood pressure include skim milk, spinach, beans, bananas and dark chocolate.

Some health conditions, as well as a person's lifestyle and genetic background, can put someone at a higher risk for developing high blood pressure. As a person cannot alter their genetic background, lifestyle changes may be necessary to reduce the chance of developing high blood pressure. These changes include getting enough exercise, limiting the amount of sodium (salt) in the diet, not being overweight, not drinking alcohol to excess, and not smoking.

Low blood pressure is not usually a concern, as long as there are no problems associated with the low pressure. Symptoms associated with low blood pressure include dizziness or lightheadedness, fainting, dehydration and unusual thirst, lack of concentration, blurred vision, nausea, and fatigue.


  • blood pressure : Pressure that circulating blood puts on the walls of blood vessels.
  • diastolic : Blood pressure when the heart is resting between beats.
  • hypertension : High blood pressure.
  • systolic : Blood pressure when the heart constricts.


  • Blood pressure occurs when circulating blood puts pressure on the walls of blood vessels.
  • Hypertension, or high blood pressure, can increase the risk of cardiovascular disease.


Use the resource below to answer the questions that follow.

  1. What causes your pulse?
  2. What is systolic pressure? How is it measured?
  3. What is diastolic pressure? How is it measured?


  1. What is the healthy range for blood pressure?
  2. Why do you think hypertension is sometimes called a silent killer?


blood pressure

blood pressure

Pressure that circulating blood puts on the walls of blood vessels.


Blood pressure when the heart is resting between beats.


High blood pressure.


Blood pressure when the heart constricts.

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Difficulty Level:

At Grade


7 , 8

Date Created:

Nov 29, 2012

Last Modified:

Jan 30, 2016
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