参考答案:
The motor neuron transmits an action potential to the neuromuscular junction.
Acetylcholine (a transmitter substance) is released, and it diffuses across the neuromuscular junction to the muscle.
The transmitter substance depolarises the muscle fibre.
Depolarisation causes the entry of calcium into the sarcoplasmic reticulum.
The muscle fibres contract, actin slides past myosin.
The sliding filaments create a force to move the limb.
The strength of contraction depends upon the frequency of impulses in the motor neurones.
The strength of contraction depends upon the number of motor neurons stimulated.
Note – this question is about the role in contraction not the details of the cell-cell communication.
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