MICROANATOMY

Detailed explanation-1: -By studying sarcomeres, the basic unit controlling changes in muscle length, scientists proposed the sliding filament theory to explain the molecular mechanisms behind muscle contraction. Within the sarcomere, myosin slides along actin to contract the muscle fiber in a process that requires ATP.

Detailed explanation-2: -According to the sliding filament theory, a muscle fiber contracts when myosin filaments pull actin filaments closer together and thus shorten sarcomeres within a fiber. When all the sarcomeres in a muscle fiber shorten, the fiber contracts.

Detailed explanation-3: -According to the sliding filament theory, the myosin (thick filaments) of muscle fibers slide past the actin (thin filaments) during muscle contraction, while the two groups of filaments remain at relatively constant length.

Detailed explanation-4: -Muscle contraction occurs when the thin actin and thick myosin filaments slide past each other. It is generally assumed that this process is driven by cross-bridges which extend from the myosin filaments and cyclically interact with the actin filaments as ATP is hydrolysed.