College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which two proteins are crucial for muscle contraction regulation?

1. Actin and Myosin

2. Tropomyosin and Troponin

3. Calcium and ATP

4. Collagen and Elastin

The correct answer is: Tropomyosin and Troponin

The correct answer highlights the critical roles of tropomyosin and troponin in the regulation of muscle contraction. These two proteins are part of the thin filament structure within muscle fibers and play essential roles in the contraction mechanism. Tropomyosin acts as a regulatory protein that wraps around actin filaments. In a relaxed muscle, tropomyosin blocks the binding sites on actin where myosin heads interact, preventing contraction. When the muscle is stimulated, calcium ions are released, which bind to troponin. This binding causes a conformational change in troponin, leading to the movement of tropomyosin away from the binding sites on actin, thereby allowing myosin to bind to actin and initiate contraction. Understanding the function of tropomyosin and troponin is vital as they are directly involved in the mechanisms that allow muscles to contract and relax in response to neural signals. This regulatory process is essential for all voluntary and involuntary muscle movements in the body. Other options, while important for muscle function in different contexts, do not directly pertain to the regulation of muscle contraction itself as specifically as tropomyosin and troponin do.