AEMCA Practice Exam

What effect does stimulation of Beta 2 receptors have on the body?

1. Increases heart rate and force of contraction

2. Causes constriction of blood vessels

3. Causes relaxation in bronchioles and smooth muscles

4. Inhibits norepinephrine release

The correct answer is: Causes relaxation in bronchioles and smooth muscles

Stimulation of Beta 2 receptors primarily results in the relaxation of bronchioles and smooth muscles. These receptors are predominantly found in the lungs and vascular smooth muscle, and their activation leads to vasodilation and bronchodilation. This means that when Beta 2 receptors are stimulated, the airways in the lungs expand, making it easier to breathe. This effect is particularly crucial in conditions such as asthma, where the airways can become constricted. The role of Beta 2 receptors in smooth muscle relaxation also extends to other areas of the body, including the uterus and gastrointestinal tract, where stimulation can result in decreased muscle tone and motility. This beneficial effect allows for improved airflow and can help alleviate respiratory distress in individuals with obstructive airway diseases. In contrast, choices regarding heart rate and force of contraction reflect the actions of Beta 1 receptors, which are primarily responsible for cardiac stimulation. The effects on blood vessels pertain more to Alpha receptors, while the inhibition of norepinephrine release typically involves feedback mechanisms that are not directly associated with Beta 2 receptor activation. Understanding the specific roles of these receptor subtypes clarifies how the body responds to different types of stimulation.