Nonselective beta blockers inhibit which receptors?

Nonselective beta blockers inhibit which receptors?

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

Answer: (C)

Nonselective beta blockers inhibit both beta-1 and beta-2 receptors. The beta-1 receptors are mainly in the heart, so blocking them reduces heart rate, contractility, and AV conduction. The beta-2 receptors are in smooth muscle of the lungs and vasculature, so blocking them can cause bronchoconstriction and reduced vasodilation. That’s why nonselective agents like propranolol affect both receptor types, unlike cardioselective agents (which mainly block beta-1). Some nonselective blockers (like carvedilol and labetalol) also block alpha receptors, but their beta-receptor activity includes inhibition of both beta-1 and beta-2.

Nonselective beta blockers inhibit both beta-1 and beta-2 receptors. The beta-1 receptors are mainly in the heart, so blocking them reduces heart rate, contractility, and AV conduction. The beta-2 receptors are in smooth muscle of the lungs and vasculature, so blocking them can cause bronchoconstriction and reduced vasodilation. That’s why nonselective agents like propranolol affect both receptor types, unlike cardioselective agents (which mainly block beta-1). Some nonselective blockers (like carvedilol and labetalol) also block alpha receptors, but their beta-receptor activity includes inhibition of both beta-1 and beta-2.