Question

By what process does the motor neuron stimulate the muscle cell?

The motor neuron creates a magnetic resonance which stimulates myofibrils to react.
Neurotransmitter is released into the synaptic cleft to cause an action potential in the muscle cell.
The action potential skips directly from the motor neuron onto the muscle cell.
The motor neuron changes shape putting pressure on the muscle cell to trigger contraction.

Answer 1

The action potential invades T-tubules and causes the L-type calcium channels to open, which in turn causes ryanodine receptors (RyRs) in the SR to open and release calcium, which stimulates contraction.