Horan, Michael National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland.
Last reviewed:May 2020
Show previous versions
- Related Primary Literature
- Additional Reading
High blood pressure. Hypertension occurs when there is a state of abnormally elevated blood pressure. Blood pressure is expressed in two numbers (see illustration): the higher number is the systolic blood pressure, which is the pressure exerted by the blood against the walls of the blood vessels while the heart is contracting; the lower number is the diastolic blood pressure, which is the residual pressure that exists between heart contractions, or while the heart is relaxing. Normal blood pressure (typically below 120/80 mmHg) provides sufficient blood flow to the vital organs, including the brain, heart, kidneys, intestine, and skeletal muscles. For diagnostic purposes, blood pressure is considered high when persistently above 140/90 mmHg. The prevalence of this clinical condition in modern society is sufficiently great to warrant its being referred to as a public health problem. See also: Blood; Blood vessel; Circulation; Circulation disorders; Heart (vertebrate); Heart disorders; Public health
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information