AEMCA Practice Exam

What is a neurotransmitter?

1. A chemical that alters gene expression

2. A chemical that is released at the end of an axon terminal

3. A chemical that binds to proteins in the nucleus

4. A chemical that is stored in the cell body

The correct answer is: A chemical that is released at the end of an axon terminal

A neurotransmitter is defined as a chemical messenger that transmits signals across a synapse from one neuron to another neuron or to a target cell, such as a muscle or gland. The correct choice highlights the role of neurotransmitters in communication between nerve cells. They are synthesized and stored in vesicles at the end of an axon terminal. When an action potential reaches the axon terminal, these neurotransmitters are released into the synaptic cleft and bind to specific receptors on the postsynaptic cell, allowing the signal to continue propagating. The other options describe functions or locations related to cellular processes but do not accurately reflect the role of a neurotransmitter. For example, while altering gene expression and binding to proteins in the nucleus are important biological processes, these actions pertain more to other types of chemical signals such as hormones or second messengers, rather than neurotransmitters. Similarly, neurotransmitters are not primarily stored in the cell body; instead, they are synthesized in the cell body but are actively packaged and stored in axon terminals for release upon stimulation. Thus, the focus on the release of neurotransmitters at the axon terminal clearly identifies their critical function in neural communication.