Emergency Medical Technician (EMT) Intermediate Practice Exam

What effect does stimulation of alpha receptors in the sympathetic nervous system have on blood vessels?

1. Peripheral vasodilation

2. Peripheral vasoconstriction

3. Increased heart rate

4. Decreased blood pressure

The correct answer is: Peripheral vasoconstriction

Stimulation of alpha receptors in the sympathetic nervous system predominantly results in peripheral vasoconstriction. Alpha-adrenergic receptors, primarily found in the smooth muscle of blood vessels, respond to catecholamines like norepinephrine and epinephrine. When these receptors are activated, it leads to the contraction of the vascular smooth muscle, resulting in an increase in vascular resistance and narrowing of the blood vessels, which elevates blood pressure. This response is a vital part of the body's mechanisms for regulating blood flow, particularly in times of stress or emergency, as it helps to redirect blood to essential organs and supports increased perfusion pressure. In contrast, other responses like vasodilation typically involve beta receptors, which mediate different effects on vascular function. Understanding this distinction is crucial for treating conditions related to blood flow and pressure.