Certified Registered Nurse Anesthetist (CRNA) Practice Exam

Which effect does beta-2 receptor stimulation have?

1. Increased heart rate

2. Vasoconstriction

3. Relaxation of bronchial smooth muscle

4. Decreased urine output

The correct answer is: Relaxation of bronchial smooth muscle

Beta-2 receptor stimulation primarily results in the relaxation of bronchial smooth muscle. This effect is particularly significant in the context of the respiratory system, where beta-2 agonists are often used as bronchodilators to alleviate conditions such as asthma and chronic obstructive pulmonary disease (COPD). By binding to beta-2 adrenergic receptors located in the smooth muscle of the airways, these agents induce relaxation, leading to bronchodilation and improved airflow. Understanding the action of beta-2 receptors also encompasses their role in other physiological processes, such as vasodilation in some vascular beds and inhibition of histamine release from mast cells. However, their most clinically relevant effect is the relaxation of bronchial smooth muscle, making this a key concept for healthcare providers, especially for those in anesthesia and respiratory care.