Washington Master Esthetics Practice Exam

What are the threadlike structures responsible for the contractile properties of muscle that allow voluntary movement?

1. Myofibrils

2. Myofilaments

3. Filaments

4. Fibers

The correct answer is: Myofilaments

The correct answer focuses on myofilaments, which are the fundamental threadlike structures within muscle cells that play a crucial role in muscle contraction. Myofilaments are composed of actin (thin filaments) and myosin (thick filaments), and their interaction is essential for the contractile properties of muscle. When a muscle contracts, the myofilaments slide past each other, leading to the shortening of the muscle fibers. This sliding filament mechanism is key to enabling voluntary movement as it allows muscles to generate force and produce motion. Myofilaments are organized into myofibrils, which are further assembled into muscle fibers, but it is the myofilaments themselves that are primarily responsible for the contractile mechanism. Understanding this distinction helps clarify the muscle contraction process and emphasizes the importance of myofilaments in both skeletal and cardiac muscles where voluntary control is necessary for movement and function.