Which statement correctly describes the effect of alpha adrenergic receptor stimulation on arterioles?

• A. Alpha Adrenergic Receptors Cause Vasoconstriction Of Arterioles
• B. Beta Adrenergic Receptors Cause Vasodilation Of Arterioles
• C. Beta Two Adrenergic Receptors Cause Bronchodilation
• D. Muscarinic Receptors Cause Vasoconstriction Of Arterioles

Answer: (A)

Stimulation of alpha adrenergic receptors on arterioles causes vasoconstriction because these receptors, mainly alpha-1 on vascular smooth muscle, activate a Gq signaling pathway that increases intracellular calcium and triggers contraction. This constricts the vessel diameter, raises systemic vascular resistance, and tends to elevate blood pressure, helping redirect blood to critical organs when sympathetic activity is high.

The other receptor types act differently in vascular beds. Beta receptors can mediate vasodilation in some arterioles (notably beta-2 in skeletal muscle), and beta-2 stimulation also causes bronchodilation in the airways. Muscarinic receptors in many vascular beds promote vasodilation via nitric oxide release from the endothelium rather than constriction. So the direct effect on arterioles when alpha receptors are stimulated is vasoconstriction.