OSMT (Ontario Society of Medical Technologists) Practice Exam

The axon terminal of a motor neuron is responsible for transmitting signals to muscle fibers, facilitating muscle contractions. In this process, the axon terminal releases a specific neurotransmitter known as acetylcholine. Acetylcholine binds to receptors on the muscle cell membrane, leading to the depolarization of the muscle fiber and ultimately triggering contraction.

In contrast to acetylcholine, sodium ions play a critical role in the generation and propagation of action potentials but are not released from the axon terminal. Cholinesterase, while important in breaking down acetylcholine after its action to prevent continuous stimulation of the muscle, is not released from the axon terminal itself. Potassium ions, like sodium, are involved in maintaining the electrical balance within the neuron but are not the substances that are exocytosed by the axon terminal to communicate with muscle cells.

Therefore, the release of acetylcholine is crucial for the communication between neurons and muscles, establishing it as the correct answer.