Beta-2 receptor effects in the lungs include which effect?

Beta-2 receptor effects in the lungs include which effect?

• A. Bronchodilation
• B. Bronchoconstriction
• C. Mucus production
• D. Ciliary movement decrease

Answer: (A)

Activation of beta-2 receptors in the lungs relaxes airway smooth muscle, producing bronchodilation. When a beta-2 agonist binds, it activates Gs protein, which stimulates adenylyl cyclase to raise cyclic AMP. The higher cAMP activates protein kinase A, reducing intracellular calcium and causing smooth muscle relaxation. The result is widened airways and easier airflow, which is why bronchodilation is the correct effect. Bronchoconstriction would come from parasympathetic (M3) stimulation or irritants, not beta-2 activation. Mucus production isn’t driven by beta-2 receptors, and beta-2 agonists can actually aid mucus clearance by increasing ciliary beat frequency rather than decreasing it.

Activation of beta-2 receptors in the lungs relaxes airway smooth muscle, producing bronchodilation. When a beta-2 agonist binds, it activates Gs protein, which stimulates adenylyl cyclase to raise cyclic AMP. The higher cAMP activates protein kinase A, reducing intracellular calcium and causing smooth muscle relaxation. The result is widened airways and easier airflow, which is why bronchodilation is the correct effect. Bronchoconstriction would come from parasympathetic (M3) stimulation or irritants, not beta-2 activation. Mucus production isn’t driven by beta-2 receptors, and beta-2 agonists can actually aid mucus clearance by increasing ciliary beat frequency rather than decreasing it.