Answer:
e. Opening of sodium channels
Explanation:
Skeletal muscle fibers are depolarized by the end-plate potential voltage. It is caused by the binding of neurotransmitter acetylcholine to the post synaptic membrane present in the neuromuscular junction. In the absence of a nerve impulse, the end plate membrane has a negative charge inside and a positive charge outside due to uneven distribution of ions. This makes the membrane polarized.
When acetylcholine is released by nerve terminal due to an impulse, it binds to the receptor molecules present on end plate. As a result, sodium channels are opened which leads to influx of sodium ions in the muscle cell. Now the membrane gets slightly depolarized. Slowly acetylcholine is degraded by an enzyme closing the channels and again polarizing the membrane.
