Emergency Medical Technician (EMT) Basic Certification Practice Exam

What physiological effect does epinephrine have on blood vessels?

1. Dilates blood vessels

2. Constricts blood vessels

3. Increases blood flow to extremities

4. Has no effect on blood vessels

The correct answer is: Constricts blood vessels

Epinephrine is a hormone and neurotransmitter that plays a crucial role in the body's fight-or-flight response. One of its primary physiological effects on vascular smooth muscle is vasoconstriction, particularly in certain vascular beds such as the skin, gastrointestinal tract, and kidneys. This effects is predominantly mediated through the activation of alpha-adrenergic receptors in the smooth muscle of blood vessels. When epinephrine binds to these alpha-adrenergic receptors, it causes the muscles to contract, leading to narrowing of the blood vessels (vasoconstriction). This mechanism helps redirect blood flow to more vital organs such as the heart, brain, and lungs during times of stress or danger, prioritizing their function above less critical areas. This response is essential for maintaining blood pressure and ensuring that oxygenated blood reaches vital organs, especially in emergency situations. While epinephrine can also act on beta-adrenergic receptors to promote vasodilation in some vascular beds like the skeletal muscles, the overall systemic effect tends to be one of vasoconstriction when considering the entire body, particularly in the context of its role in acute stress responses. Therefore, the physiological effect of epinephrine on blood vessels is primarily characterized by constriction, which aligns with