Question

What is the predominant \( \beta \)-adrenoceptor in bronchial smooth muscle?

• A. \( \beta_1 \)-adrenoceptor
• B. \( \beta_2 \)-adrenoceptor
• C. \( \beta_3 \)-adrenoceptor
• D. \( \beta_4 \)-adrenoceptor

Answer 1

The Correct Option is B

Step 1: Understanding Beta-Adrenoceptors - Beta-adrenoceptors (β-receptors) are G-protein-coupled receptors that mediate the effects of epinephrine and norepinephrine. - They are classified into three main types: β₁, β₂, and β₃.


Step 2: Evaluating the Predominant Receptor in Bronchial Smooth Muscle - \( \beta_1 \)-adrenoceptors are primarily found in the heart and kidneys, where they mediate cardiac contractility and renin release. - \( \beta_2 \)-adrenoceptors are predominantly located in the bronchial smooth muscle, where they cause bronchodilation when stimulated. - \( \beta_3 \)-adrenoceptors are mainly found in adipose tissue, where they regulate lipolysis. - \( \beta_4 \)-adrenoceptors are not well characterized and have uncertain physiological significance.


Step 3: Selecting the Correct Answer - Since \( \beta_2 \)-adrenoceptors are responsible for bronchodilation, the correct choice is (B) \( \beta_2 \)-adrenoceptor.