Sarcomeres sliding filament model

Studies on muscle contraction carried out between 1930 and 1960 heralded the modem era of research on cytoskeletal stmctures. Actin and myosin were identified as the major contractile proteins of muscle, and detailed electron microscopic studies on sarcomeres by H.E. Huxley and associates in the 1950s produced the concept of the sliding filament model, which remains the keystone to an understanding of the molecular mechanisms responsible for cytoskeletal motility. 

The sliding filament model describes the mechanism involved in muscle contraction. In this model, sarcomeres become shorter when the thin and thick filaments slide alongside each other and telescope together, with ATP being consumed. During contraction, the following reaction cycle is repeated several times ... 

The sliding-filament model of muscle contraction. During contraction, the thick and thin filaments slide past each other so that the overall length of the sarcomere becomes shorter. 

An early test of the sliding filament model was the very careful measurement by Gordon et al. (1966) of the active tension produced by the muscle at different sarcomere lengths (Fig. 7B-D). If the myosin heads or crossbridges act as independent force generators, then, as the sarcomere length... 

The sliding filament model explains the molecular basis by which muscular contraction occurs. During muscular contraction, thin filaments within the sarcomere of a myofibril are pulled towards the center of the sarcomere (called the H zone) by the thick filaments. In the process, the sarcomeric length shortens and the myofibril shortens. As a result, the muscle contracts (see Figure 8.11). Steps in the process include the following ... 

---