Muscle contraction
Activation of tension-generating sites in muscle
Muscle contraction
Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length (isometric contraction), such as when holding something heavy in the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state. For the contractions to happen, the muscle cells must rely on the interaction of two types of filament: thin and thick filaments. The major constituent of thin filaments is a chain formed by helical coiling of two strands of actin, and thick filaments predominantly consist of chains of the motor-protein myosin. Together, these two filaments form myofibrils - the basic functional organelles in the skeletal muscle system. In vertebrates, skeletal muscle contractions are neurogenic as they require synaptic input from motor neurons...
Read on Wikipedia · Image Daniel Walsh and Alan Sved, CC BY-SA 4.0
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