Question

Acetylcholine is a neurotransmitter that is important in the transmission of signals from motor neurons to the muscles. Which of the following describes the action of acetylcholine?
A. Acetylcholine travels through the nerve fibres to the muscle cell where it breaks down inhibitors blocking the active sites on the muscle cell.
B. Acetylcholine triggers the production of other neurotransmitters in the muscle cell. The new neurotransmitters stimulate contraction
C. Acetylcholine is released from the axon of the motor neuron, diffuses across the synapse and binds to receptors on the muscle cell, leading to contraction.
D. Acetylcholine binds to G-protein receptors on the muscle cell, resulting in the production of cAMP within the muscle cells. cAmp then stimulates transcription.

Answer 1

Acetylcholine (ACh) acts as a neurotransmitter in the brain and the body of humans. It is a chemical messenger produced by nerve cells to send signals to other cells, such as neurons, muscle cells and cells of the gland. Its name is derived from its chemical structure: it is an acetic acid and choline ester.

Complete answer: A neuronal signal hitting the neuromuscular junction activates an acetylcholine neurotransmitter that produces the potential for action in the sarcolemma. This spreads and induces the release of calcium ions into the sarcoplasm through the muscle fibre. Increasing the number of calcium ions contributes to the binding of calcium on actin filaments with a subunit of troponin and thus, prevents the masking of myosin active sites and facilitates muscle contraction. Acetylcholine is then released from the axon of the motor neuron, diffuses through the synapse, and attaches to muscle cell receptors, contributing to contraction. Therefore, Acetylcholine is released from the axon of the motor neuron, diffuses through the synapse and then attaches to the muscle cell receptors, leading to contraction. Hence, option C is the correct statement which describes the action of acetylcholine.
Hence, option C is the correct answer.

Note: An important link between the brain and the muscles is the acetylcholine receptor. Many organisms excrete toxins that cause paralysis by blocking the acetylcholine receptor. Low levels of acetylcholine have been associated with impaired learning and memory, as well as brain disorders such as dementia and Alzheimer's disease.