beta

beta

 [ba´tah]

second letter of the Greek alphabet, β; used to denote the second position in a classification system. Often used in names of chemical compounds to distinguish one of two or more isomers or to indicate the position of substituent atoms or groups in certain compounds. Also used to distinguish types of radioactive decay; brain rhythms or waves; adrenergic receptors; secretory cells of the various organs of the body that stain with basic dyes, such as the beta cells of the pancreas; and the type of hemolytic streptococci that produce a zone of decolorization when grown on blood media.

beta-adrenergic blocking agent (beta-blocker) any of a group of drugs that block the action of epinephrine at beta-adrenergic receptors on cells of effector organs. There are two types of these receptors: β₁-receptors in the myocardium and β₂-receptors in the bronchial and vascular smooth muscles. The principal effects of beta-adrenergic stimulation are increased heart rate and contractility, vasodilation of the arterioles that supply the skeletal muscles, and relaxation of bronchial muscles.

Because of their effects on the heart, these agents are used to treat angina pectoris, hypertension, and cardiac arrhythmias. And, because they decrease the workload of the heart, they are effective in reducing the long-term risk of mortality and reinfarction after recovery from the acute phase of a myocardial infarction. They are an important adjunct in treatment of heart failure and are also used for prophylaxis of migraine.

Nonselective beta-adrenergic blocking agents affect both types of receptors and can produce bronchospasm in patients with asthma or chronic obstructive pulmonary disease. If such patients need one of these drugs, they should be given a cardioselective one that preferentially blocks the β₁-receptors in the heart.

Nonselective agents include propranolol (Inderal), used for treatment of angina, hypertension, arrhythmias, and migraine and for prophylaxis after the acute phase of a myocardial infarction; nadolol (Corgard), used for treatment of angina and hypertension; and timolol, used as an ophthalmic preparation (Timoptic) for treatment of glaucoma and as an oral preparation (Blocadren) for treatment of hypertension and for prophylaxis after the acute phase of a myocardial infarction. Cardioselective beta-adrenergic blocking agents are used for treatment of hypertension and include atenolol (Tenormin) and metoprolol (Lopressor).

beta particles negatively charged particles emitted by radioactive elements, the result of disintegration of neutrons; their source is the unstable atoms of radioactive metals such as radium and uranium. There are three general types of emissions from radioactive substances: alpha and beta particles and gamma rays. Beta particles are less penetrating than gamma rays and may be used to treat certain conditions on or near the surface of the body. See also radiation and radiation therapy.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

β

In typography, do not substitute the German compound letter β for this Greek letter.

1. Second letter of the Greek alphabet, beta.

2. chemistry denotes the second in a series, the second carbon from a functional (for example, carboxylic) group, or the direction of a chemical bond toward the viewer. For terms having this prefix, see the specific term.

3. Pressure coefficient.

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be·ta (β),

(bā'tă), In typography, do not substitute the German compound letter β for the Greek letter β.

Second letter of the Greek alphabet, β (see entry at start of letter "Bs.")

[G.]

Farlex Partner Medical Dictionary © Farlex 2012

beta

Medspeak
The second letter in the Greek alphabet. The term is included here to flag the differences in pronunciation between British and American English. 
Medspeak-UK: pronounced, BEE tuh.
Medspeak-US: pronounced, BAY tuh.
 
Statistics
The probability of a Type-II false-negative error. In hypothesis testing, beta is the probability of concluding incorrectly that an intervention is not effective when it has true effect. 1-b is the power to detect an effect of an intervention if one truly exists

Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

beta

β The second letter of the Greek alphabet; Statistics The probability of a Type II–false-negative error. See Type II error. Cf Alpha.

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

β

Abbreviation for beta.

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be·ta

(β) (bā'tă)

1. Second letter of the Greek alphabet.

2. chemistry Denotes the second in a series, the second carbon from a functional (e.g., carboxylic) group, or the direction of a chemical bond toward the viewer. For terms with the prefix β, see the specific term.

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

beta

The second letter of the Greek alphabet, often used to denote the order in a sequence.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005