Cardiac Medicine Certification (CMC) Practice Exam

What is the role of Epinephrine in the cardiovascular system?

1. Causes systemic vasodilation

2. Decreases heart rate

3. Increases cardiac output

4. Inhibits cardiac beta-receptors

The correct answer is: Increases cardiac output

Epinephrine plays a significant role in the cardiovascular system primarily by increasing cardiac output, which is achieved through multiple mechanisms. It acts on beta-1 adrenergic receptors in the heart, leading to an increase in heart rate (positive chronotropic effect) and an increase in the force of contraction (positive inotropic effect). This dual action enhances the heart's ability to pump blood more effectively, resulting in improved cardiac output. Additionally, epinephrine also stimulates beta-2 adrenergic receptors in vascular smooth muscle, which can lead to vasodilation in certain vascular beds. However, its predominant effect in acute settings is the overall increase in cardiac output due to the increased heart rate and contractility, making it a vital component in addressing cardiovascular challenges, particularly during shock or cardiac arrest. The other options do not accurately reflect the role of epinephrine in the cardiovascular system. For instance, systemic vasodilation is not the primary action of epinephrine; instead, it often causes systemic vasoconstriction in most vascular territories, particularly at higher doses. Furthermore, epinephrine does not decrease heart rate; it typically increases it. Inhibiting cardiac beta-receptors is contrary to the action of epinephrine, as it stimulates these