Beta receptors

Q: Activation of beta-3 receptors may reduce heart contractility.

A) True

B) False

Answer: A

Very seldom described, but there are three types of beta receptors:

Beta 1 is primarily in the heart muscle. Activation of these receptors results in tachycardia, increased contractility, increased atrioventricular (AV) conduction, and decreased AV node refractoriness.

Beta 2, although found in heart muscles, is more prominent in bronchial and peripheral vascular smooth muscle. Their activation results in vasodilation and bronchodilation.

Beta 3, which is not frequently described, is found in the heart as well as adipose tissues. Activation of these receptors may mediate catecholamine-induced thermogenesis and tend to reduce cardiac contractility.

#physiology

#cardiology

References:

1. Wachter SB, Gilbert EM. Beta-adrenergic receptors, from their discovery and characterization through their manipulation to beneficial clinical application. Cardiology. 2012;122(2):104-12. doi: 10.1159/000339271. Epub 2012 Jul 3. PMID: 22759389.

2. De Blasi A. Beta-adrenergic receptors: structure, function and regulation. Drugs Exp Clin Res. 1990;16(3):107-12. PMID: 1974837.