The correct answer is:
• motor neuron action potential,
The contraction of a muscle cell begins with the nerve impulse arriving at the neuromuscular junction (motor neuron muscle cell junction)
• neurotransmitter release,
When action potential gets to the end of motor neuron it triggers it to release neurotransmitters which will bind to its receptor on the muscle cell
• muscle cell action potential,
Binding of the neurotransmitter to its receptor on the muscle cell will fire its own action potential.
• release of calcium ions from SR,
The nerve impulse is carried to the sarcoplasmic reticulum (SR) and consequently Ca2+ channels open , Ca2+ leave the sarcoplasmic reticulum and attach to troponin – the protein molecules that are situated on actin filaments.
• ATP-driven power stroke,
Active sites of actin are open thanks to Ca2+ and myosin heads can bind to them, using the ATP energy
• sliding of myofilaments
Contraction occurs.
