- Myofibril: A cylindrical organelle running the length of the muscle fibre, containing Actin and Myosin filaments.
- Sarcomere: The functional unit of the Myofibril, divided into I, A and H bands.
- Actin: A thin, contractile protein filament, containing 'active' or 'binding' sites.
- Myosin: A thick, contractile protein filament, with protusions known as Myosin Heads.
- Tropomyosin: An actin-binding protein which regulates muscle contraction.
- Troponin: A complex of three proteins, attached to Tropomyosin.