American Board of Psychiatry and Neurology (ABPN) Practice Exam 2025 - Free ABPN Practice Questions and Study Guide

The statement regarding exocytosis is the one that is not accurate in the context of chemical signaling between neurons. Exocytosis specifically refers to the process by which neurotransmitters packaged in vesicles within the presynaptic neuron are released into the synaptic cleft following their fusion with the presynaptic membrane. This process is initiated by an influx of calcium ions (Ca2+) when an action potential reaches the axon terminal, triggering the release of these neurotransmitters into the synaptic cleft where they can then bind to postsynaptic receptors. Therefore, it does not pertain to the diffusion of neurotransmitters; rather, diffusion occurs after exocytosis, when the neurotransmitters have already been released into the synapse.

In contrast, the synthesis of neurotransmitters can be stimulated by Ca2+ influx, as this signals the neuron's activity and can promote the synthesis process. The action of presynaptic α receptors in neurons releasing norepinephrine is to provide inhibitory feedback, reducing norepinephrine release to modulate neuronal signaling. Lastly, monoamine oxidase type B does indeed metabolize neurotransmitters such as norepinephrine and serotonin, which is fundamental to the regulation of these neurotransmitters in the syn