Question

movement of sodium ions into the muscle cell at the neuromuscular junction causes
multiple choice
release of acetylcholine
repolarization of the muscle cell membrane
re - uptake of acetylcholine
depolarization of the muscle cell membrane

Explanation:

When sodium ions ($Na^+$) move into the muscle cell at the neuromuscular junction, the positive - charged sodium ions increase the positive charge inside the cell relative to the outside. This change in the charge distribution across the cell membrane leads to depolarization. Acetylcholine release is triggered by an action potential arriving at the axon terminal, not by sodium - ion influx into the muscle cell. Repolarization occurs when potassium ions ($K^+$) move out of the cell after depolarization. Re - uptake of acetylcholine is a process that terminates the action of acetylcholine at the synapse and is not related to sodium - ion influx into the muscle cell.

Answer:

Depolarization of the muscle cell membrane