Stimulation causes bronchodilation via which receptor?

• A. Alpha One Adrenergic Receptors
• B. Beta One Adrenergic Receptors
• C. Beta Two Adrenergic Receptors
• D. Muscarinic Receptors

Answer: (C)

Bronchodilation from receptor stimulation is driven by beta-2 adrenergic receptors on airway smooth muscle. When these receptors are activated, they couple to Gs proteins that stimulate adenylate cyclase, increasing cyclic AMP. The rise in cAMP activates protein kinase A, which reduces myosin light-chain kinase activity and promotes relaxation of the smooth muscle, widening the airways. This is why beta-2 agonists like albuterol are effective bronchodilators during airway constriction. Other receptors listed have different roles: alpha-1 activation mainly causes vasoconstriction and isn’t the primary driver of bronchodilation; beta-1 receptors affect the heart; muscarinic receptors tend to promote bronchoconstriction when stimulated. So, stimulation of beta-2 adrenergic receptors best produces bronchodilation.