Certified Registered Nurse Anesthetist (CRNA) Practice Exam

Which receptors primarily mediate the vasodilatory effects associated with beta-2 stimulation?

1. Alpha 1

2. Beta 1

3. Beta 2

4. Alpha 2

The correct answer is: Beta 2

The receptors that primarily mediate the vasodilatory effects associated with beta-2 stimulation are indeed the beta-2 adrenergic receptors. These receptors are predominantly located in vascular smooth muscle and other tissues such as the lungs and uterus. When beta-2 receptors are stimulated by endogenous catecholamines, like epinephrine, or by agonistic drugs, they lead to relaxation of smooth muscle and subsequent vasodilation. The mechanism involves the activation of adenylate cyclase, which increases the levels of cyclic AMP (cAMP) within cells. Elevated cAMP results in the activation of protein kinase A (PKA), which ultimately leads to smooth muscle relaxation and vasodilation. This is particularly important in clinical settings, where understanding the role of beta-2 receptors can help guide the use of certain medications for managing conditions that may require vasodilation, such as asthma or acute hypertension. In contrast, other receptor types listed have different roles in the vascular system. Alpha-1 receptors are primarily responsible for vasoconstriction, beta-1 receptors are mainly involved in increasing heart rate and contractility, and alpha-2 receptors can inhibit further release of norepinephrine, which does not primarily contribute to vasodilation. Understanding the specific actions