Final answer:
The five steps of muscle contraction in order are: neurotransmitter release, calcium release, tropomyosin shifting, cross-bridge formation, and power stroke.
Step-by-step explanation:
- The motor neuron releases the neurotransmitter ACh at the neuromuscular junction.
- An action potential travels along the sarcolemma, triggering the release of calcium from the sarcoplasmic reticulum.
- Calcium binds to troponin, causing tropomyosin to shift away from the myosin-binding sites on actin.
- Myosin heads bind to the exposed actin-binding sites, forming cross-bridges.
- The myosin heads undergo the power stroke, pulling the thin filaments past the thick filaments and causing muscle contraction.