Question

Following muscle contraction in response to a stimulus, the muscle temporarily cannot respond. This is known as:

• A. Refractory period
• B. Motor end plate
• C. Oxygen debt
• D. Summation period

Answer 1

Answer: (A)

Refractory period

• 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.
• Muscle cannot always respond to the stimulus due to fatigue and production of lactic acid this period is called refractory period.
• So, the correct option is 'refractory period'.