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Multiple Choice
Movement of sodium ions into the muscle cell at the neuromuscular junction causes which of the following?
A
Depolarization of the muscle cell membrane
B
Release of calcium ions from the synaptic vesicles
C
Inhibition of acetylcholine release
D
Hyperpolarization of the muscle cell membrane
Verified step by step guidance
1
Understand the context: The neuromuscular junction is the site where a motor neuron communicates with a muscle cell to initiate contraction. Sodium ions play a key role in this process by altering the electrical charge across the muscle cell membrane.
Recall the concept of depolarization: Depolarization occurs when the inside of a cell becomes less negative compared to the outside. Sodium ions entering the muscle cell reduce the negative charge inside, leading to depolarization.
Eliminate incorrect options: Hyperpolarization is the opposite of depolarization, where the inside of the cell becomes more negative. Sodium ion influx does not cause hyperpolarization, so this option can be ruled out.
Consider the role of calcium ions: Calcium ions are released from the sarcoplasmic reticulum within the muscle cell during contraction, not from synaptic vesicles. Sodium ion movement does not directly cause calcium release from synaptic vesicles, so this option is incorrect.
Evaluate acetylcholine inhibition: Sodium ion influx does not inhibit acetylcholine release. Instead, acetylcholine is released from the motor neuron to stimulate sodium ion entry into the muscle cell. Therefore, this option is also incorrect, leaving depolarization as the correct answer.