Question

For a skeletal muscle to contract, what should happen first?

• A. ATP must be completely broken down
• B. A nerve must stimulate the muscle
• C. A muscle must stimulate a nerve
• D. A bone must move

Answer 1

The correct option is B A nerve must stimulate the muscle

• Myofibril activity is required for muscle contraction on the molecular level.
  
• When ATP binds to myosin, it separates from the actin of the myofibril, which causes a contraction.
• The muscle contraction cycle is triggered by calcium ions binding to the protein complex troponin, exposing the active-binding sites on the actin.
• ATP then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.

So, the correct option is 'A nerve must stimulate the muscle'.