What makes up a muscle fibre?

Muscle fibers are made up of myofibrils, which are the contractile units of muscle tissue. Each muscle fiber contains multiple myofibrils, and these structures are responsible for the force generation during muscle contraction. Myofibrils are themselves composed of repeating units called sarcomeres, which are the functional units of contraction within the myofibrils.

While sarcomeres, myosin, and actin play crucial roles in contraction, they are components within the myofibrils. Myosin and actin are specific proteins that form the thick and thin filaments, respectively, within the sarcomeres. The organized arrangement of these myofibrils and their associated components allows muscle fibers to contract effectively. Therefore, identifying myofibril as the fundamental building block of muscle fibers correctly highlights their structural importance in muscle function.