Which statement about alpha-1 receptor stimulation is true?

• A. It causes vasoconstriction
• B. It causes bronchodilation
• C. It increases insulin secretion
• D. It decreases heart rate

Answer: (A)

Stimulation of alpha-1 receptors on vascular smooth muscle causes vasoconstriction. When these receptors are activated, a Gq signaling cascade increases intracellular calcium, leading to contraction of the vessel walls. The result is narrowed arterioles and venules, which raises systemic vascular resistance and blood pressure.

This is why the statement about alpha-1 stimulation being associated with vasoconstriction is true. Bronchodilation is driven mainly by beta-2 receptors in the airways, not alpha-1. Insulin secretion is not directly increased by alpha-1 activity (sympathetic effects on insulin are more nuanced and often inhibitory via other receptors). Directly decreasing heart rate is not a primary effect of alpha-1 stimulation; heart rate is more directly influenced by beta-1 activity and reflex responses to blood pressure changes.