Certified Registered Nurse Anesthetist (CRNA) Practice Exam

Which types of receptors are activated by epinephrine?

1. Alpha 1 and beta 1

2. Alpha 2 and beta 2

3. Alpha 1, alpha 2, beta 1, beta 2

4. Only beta 1 and beta 2

The correct answer is: Alpha 1, alpha 2, beta 1, beta 2

Epinephrine activates multiple adrenergic receptors, which include alpha 1, alpha 2, beta 1, and beta 2 receptors. This broad activation is what makes epinephrine a powerful and versatile medication in clinical situations. Alpha 1 receptors, when activated, lead to vasoconstriction and an increase in blood pressure. Alpha 2 receptors have a role in inhibiting further release of norepinephrine and can lead to sedation. Beta 1 receptors, predominantly found in the heart, influence heart rate and contractility, increasing cardiac output. Lastly, beta 2 receptors are found in the smooth muscle of the airways and blood vessels, and their activation results in vasodilation and bronchodilation, enhancing airflow and reducing resistance in the airway. The comprehensive receptor activity of epinephrine underlies its critical function in the body’s fight-or-flight response and its use in emergency medicine, such as in anaphylactic shock and cardiac arrest, where rapid and varied physiological responses are necessary. Therefore, the inclusion of all four types of receptors—alpha 1, alpha 2, beta 1, and beta 2—in the answer accurately reflects the pharmacological action of epinephrine.