Arrange the steps in the correct order to explain how a muscle fiber contracts. Myosin and actin protein filaments attach to eac
h other. Calcium ions release into the myofibrils. Myosin filaments pull on the actin filaments. The nerve impulse reaches the neuromuscular junction. The motor neuron carries the nerve impulse. The sarcomere shortens. ↓ ↓ ↓ ↓ ↓
The nerve impulse reaches the neuromuscular junction.
↓
Calcium ions release into the myofibrils.
↓
Myosin and actin protein filaments attach to each other.
↓
Myosin filaments pull on the actin filaments.
↓
The sarcomere shortens.
The neurotransmitter (ACh) from motor neurons signals a muscle fiber to depolarize. The depolarization (Na+) will trigger Ca++ release and will initiate contraction by binding to troponin. Myosin pulls the actin strands. ATP sustains the contraction.
