A type of adrenergic receptor that primarily mediates vasoconstriction and increases peripheral resistance, leading to elevated blood pressure.

• A. Beta-agonists
• B. Alpha 1 receptors
• C. Chemoreceptors
• D. Smooth muscle

Answer: (B)

Activation of alpha-1 adrenergic receptors on vascular smooth muscle causes vasoconstriction, raising peripheral vascular resistance and increasing blood pressure. These receptors are Gq-coupled, so their stimulation triggers phospholipase C activity, producing IP3 and DAG, which raise intracellular calcium and cause smooth muscle contraction in arterioles. This mechanism explains why alpha-1 activity elevates blood pressure. Beta receptors can influence heart rate and some dilation (beta-2), but they don’t primarily drive vasoconstriction. Chemoreceptors are sensing changes in blood chemistry, not matching the action of constricting blood vessels. Smooth muscle is the tissue that contracts, not the receptor type itself.