ANATOMY

Detailed explanation-1: -Myofibrils are composed of long proteins including actin, myosin, and titin, and other proteins that hold them together. These proteins are organized into thick, thin, and elastic myofilaments, which repeat along the length of the myofibril in sections or units of contraction called sarcomeres.

Detailed explanation-2: -Answer and Explanation: Actin-or myosin-containing structure is called the myofibrils. The sarcoplasm of the muscle fibers contains many threadlike structures called the myofibrils, which extend the length of the muscle fiber.

Detailed explanation-3: -The myofibrils are made up of thick and thin myofilaments, which give the muscle its striped appearance. The thick filaments are composed strands of the protein myosin, and the thin filaments are strands of the protein actin, along with two other muscle regulatory proteins, tropomyosin and troponin.

Detailed explanation-4: -The myofibrils are bundles of interconnected protein filaments of striated muscles. The filaments (myofilaments) included in the myofibrils are mainly thick filaments (myosin), and thin filaments (actin).

Detailed explanation-5: -Myofibrils constitute the contractile system, which consists of four complex proteins: myosin, actin, tropomyosin, and troponin. These four proteins are arranged into a functional unit called a sarcomere (see Fig.