Epinephrine activating beta-2 receptors on post-synaptic vascular smooth muscle produces what effect?

Epinephrine activating beta-2 receptors on post-synaptic vascular smooth muscle produces what effect?

• A. Vasoconstriction
• B. Bronchodilation
• C. No effect
• D. Vasodilation

Answer: (D)

Activating beta-2 receptors on vascular smooth muscle causes the muscle to relax, leading to vasodilation. This happens because beta-2 stimulation increases cAMP via Gs protein, which activates protein kinase A. The rise in cAMP reduces intracellular calcium and inhibits pathways that promote contraction, resulting in smooth muscle relaxation. In skeletal muscle beds, epinephrine preferentially binds beta-2 receptors, causing vasodilation, whereas alpha-1 effects (more prominent with other catecholamines like norepinephrine) would cause constriction in different vascular beds. So, the direct effect of epinephrine on beta-2–bearing vascular smooth muscle is vasodilation.

Activating beta-2 receptors on vascular smooth muscle causes the muscle to relax, leading to vasodilation. This happens because beta-2 stimulation increases cAMP via Gs protein, which activates protein kinase A. The rise in cAMP reduces intracellular calcium and inhibits pathways that promote contraction, resulting in smooth muscle relaxation. In skeletal muscle beds, epinephrine preferentially binds beta-2 receptors, causing vasodilation, whereas alpha-1 effects (more prominent with other catecholamines like norepinephrine) would cause constriction in different vascular beds. So, the direct effect of epinephrine on beta-2–bearing vascular smooth muscle is vasodilation.