In muscles, the protein filaments myosin and actin make up the thick and thin filaments, respectively. During contraction, these filaments slide over one another in a series of repeated movements.
Actin filaments are composed of actin, tropomyosin, and troponin proteins. Myosin filaments are composed of myosin and meromyosin proteins. Cross bridges. No cross-bridges are present in actin filaments. Myosin form cross-bridges.
