The influx of Blank______ into the motor neuron ending causes the secretion of acetylcholine.Multiple choice question.cholinesodiumcalciumATP

Explanation of the Question

In this multiple-choice question, you are asked to identify which substance's influx into the motor neuron ending triggers the secretion of acetylcholine. This process is crucial for synaptic transmission at the neuromuscular junction, where nerves communicate with muscles.

Relevant Concepts

The secretion of neurotransmitters, such as acetylcholine, is typically triggered by the arrival of an action potential at the neuron's terminal, which leads to the opening of specific ion channels. The influx of certain ions can stimulate the vesicles containing neurotransmitters to fuse with the neuron's membrane and release their contents into the synaptic cleft.

Determining the Correct Answer

1. Choline: This is a precursor to acetylcholine and does not trigger its release.
2. Sodium (Na⁺): While sodium ions are essential for action potentials, they do not directly cause the release of acetylcholine.
3. Calcium (Ca²⁺): The influx of calcium ions is well-known as a critical factor in neurotransmitter release. When the action potential reaches the nerve terminal, voltage-gated calcium channels open, allowing Ca²⁺ to flow into the neuron. This influx leads to the fusion of acetylcholine vesicles with the cell membrane and subsequent release into the synaptic cleft.
4. ATP: While ATP is important for energy in cellular processes, it does not directly cause the secretion of acetylcholine.

Final Answer

The correct answer is calcium. The influx of calcium ions into the motor neuron ending causes the secretion of acetylcholine.