Blood pressure
Say it: BLUD PRESH-ur
Blood pressure is the force that circulating blood exerts on the walls of the arteries, recorded as systolic over diastolic pressure in mm Hg.
Also: BP
Definition
What is blood pressure?
Blood pressure is the pressure that blood exerts on the walls of blood vessels as the heart pumps it around the body. Used on its own, the term means the pressure in the large arteries, usually measured at the upper arm with an inflatable cuff. It is written as two numbers in millimeters of mercury (mm Hg). The higher, systolic pressure is reached when the ventricles contract; the lower, diastolic pressure is the minimum between beats, while the ventricles relax. A typical healthy adult reading is about 120/80 mm Hg, and readings that stay at or above 130/80 are classed as high blood pressure, or hypertension, under current US guidelines.
Blood pressure depends mainly on cardiac output, blood volume and the resistance of the blood vessels. Resistance is set chiefly by vessel width: even a small narrowing of the arterioles raises resistance sharply, which makes these small arteries the body's main control point. Pressure falls steadily as blood moves from the arteries through the capillaries to the veins. The nervous system, the kidneys and several hormones keep it within a working range from moment to moment.
High blood pressure usually causes no symptoms, yet over years it damages the heart, brain, kidneys and eyes and raises the risk of heart attack and stroke.
Practice it
Where you'll meet it
Quizzes that use it
Articles about it
Related
Terms that go with it
- HypertensionHypertension is a long-term condition in which the pressure of blood against artery walls stays higher than normal, straining the heart and vessels.
- Cardiac outputCardiac output is the volume of blood each ventricle of the heart pumps in one minute, equal to heart rate multiplied by stroke volume.
- HeartThe heart is the hollow, muscular organ in the chest whose four chambers pump blood through the lungs and then around the rest of the body.
- HomeostasisHomeostasis is the body's ability to keep internal conditions, such as temperature, blood glucose and pH, steady while conditions around it change.
- StrokeA stroke is a sudden loss of brain function that happens when an artery supplying the brain is blocked or bursts and bleeds.
- KidneyThe kidneys are two bean-shaped organs that filter the blood to make urine, balancing the body's water, salts and acid and helping set blood pressure.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Anatomy and Physiology 2e, 20.2 Blood Flow, Blood Pressure, and Resistance
- CDC: About High Blood Pressure
Last updated
Spotted a mistake? Tell us and we'll correct it.
Practice Physiology
Free physiology quizzes, with an explanation for every answer.
See the Quizzes