Which receptor subtype is associated with vasodilation in skeletal muscle and bronchial smooth muscle?

Which receptor subtype is associated with vasodilation in skeletal muscle and bronchial smooth muscle?

• A. Beta-1 receptors
• B. Beta-2 receptors
• C. Alpha-1 receptors
• D. Alpha-2 receptors

Answer: (B)

Beta-2 adrenergic receptors mediate smooth muscle relaxation, leading to vasodilation in skeletal muscle and bronchodilation in the airways. When activated, these receptors couple to Gs proteins and stimulate adenylyl cyclase, increasing cyclic AMP. The rise in cAMP activates protein kinase A, which lowers intracellular calcium and reduces myosin light-chain kinase activity, causing relaxation of the smooth muscle. This results in increased blood flow to active muscles and wider airways, matching the physiological needs during sympathetic activation. In contrast, alpha-1 receptors cause vasoconstriction, beta-1 receptors mainly affect heart function, and alpha-2 receptors modulate neurotransmitter release, so they don’t produce the same vasodilatory effects in these tissues.

Beta-2 adrenergic receptors mediate smooth muscle relaxation, leading to vasodilation in skeletal muscle and bronchodilation in the airways. When activated, these receptors couple to Gs proteins and stimulate adenylyl cyclase, increasing cyclic AMP. The rise in cAMP activates protein kinase A, which lowers intracellular calcium and reduces myosin light-chain kinase activity, causing relaxation of the smooth muscle. This results in increased blood flow to active muscles and wider airways, matching the physiological needs during sympathetic activation. In contrast, alpha-1 receptors cause vasoconstriction, beta-1 receptors mainly affect heart function, and alpha-2 receptors modulate neurotransmitter release, so they don’t produce the same vasodilatory effects in these tissues.