AEMCA Practice Exam

What kind of actions do alpha 2 receptors produce and where are they located?

1. Inhibit norepinephrine release; located on the postsynaptic sites

2. Enhance neurotransmitter release; located in the adrenal medulla

3. Inhibit norepinephrine release; located on pre and post ganglionic sites

4. Produce effects of vasodilation; located in the blood vessels

The correct answer is: Inhibit norepinephrine release; located on pre and post ganglionic sites

Alpha-2 receptors are primarily inhibitory in function, meaning that their activation generally leads to a decrease in the release of norepinephrine, a key neurotransmitter in the autonomic nervous system. This effect plays a crucial role in regulating blood pressure and sympathetic outflow. These receptors are predominantly located on the presynaptic nerve terminals, and their presence can also be noted at some postsynaptic sites. This strategic position allows alpha-2 receptors to provide feedback inhibition; when stimulated, they inhibit the release of norepinephrine from the presynaptic neuron, thus modulating neurotransmission and maintaining balance in the sympathetic nervous system's activity. In contrast, specific receptor locations and actions contributing to the overall function of the autonomic nervous system differentiate alpha-2 receptors from other options provided. For instance, enhancing neurotransmitter release or being located exclusively in the adrenal medulla does not accurately describe the role of alpha-2 receptors. Similarly, the effects of vasodilation and receptor location in blood vessels do not pertain to the characteristics of alpha-2 receptors, which are mainly associated with inhibition rather than direct vascular actions.