Advanced Dental Admission Test (ADAT)

What effect do A2 adrenergic receptors have?

1. Increased heart rate

2. Relaxation

3. Vasoconstriction

4. Increased respiratory rate

The correct answer is: Relaxation

A2 adrenergic receptors, when activated, primarily play a role in inhibitory functions in the autonomic nervous system. Their activation leads to a reduction in sympathetic nervous system output, which can result in sedation and relaxation. This is significant because the stimulation of A2 receptors inhibits the release of norepinephrine and leads to a decrease in overall sympathetic activity. In the cardiovascular system, for example, activation of A2 adrenergic receptors can lead to a lowering of heart rate and a reduction in blood pressure due to decreased vascular resistance. This is contrary to what might be observed with activation of other adrenergic receptors that promote increased heart rate or vasoconstriction. Thus, the effect of relaxation correlates with the activation of A2 adrenergic receptors, and their role in mediating calming responses is a key aspect of understanding how these receptors function within the autonomic system.