Which receptor is primarily responsible for bronchodilation?

Which receptor is primarily responsible for bronchodilation?

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

Answer: (B)

Bronchodilation is driven by beta-2 adrenergic receptors on bronchial smooth muscle. When these receptors are activated by sympathetic agonists, they stimulate a Gs protein to raise cyclic AMP, which relaxes the smooth muscle and widens the airways. This is the primary mechanism behind inhaled beta-2 agonists like albuterol that relieve bronchospasm. Beta-1 receptors are mainly in the heart and affect heart rate and contractility, not airway tone. Alpha-1 receptors cause vasoconstriction in vascular smooth muscle, not bronchodilation. Dopaminergic receptors have other roles in the body and do not primarily control airway dilation.

Bronchodilation is driven by beta-2 adrenergic receptors on bronchial smooth muscle. When these receptors are activated by sympathetic agonists, they stimulate a Gs protein to raise cyclic AMP, which relaxes the smooth muscle and widens the airways. This is the primary mechanism behind inhaled beta-2 agonists like albuterol that relieve bronchospasm. Beta-1 receptors are mainly in the heart and affect heart rate and contractility, not airway tone. Alpha-1 receptors cause vasoconstriction in vascular smooth muscle, not bronchodilation. Dopaminergic receptors have other roles in the body and do not primarily control airway dilation.