If the muscle length shortens, the contraction is concentric if the muscle length lengthens, the contraction is eccentric. In contrast, a muscle contraction is isotonic if muscle tension remains the same throughout the contraction. A muscle contraction is described as isometric if the muscle tension changes but the muscle length remains the same. Muscle contraction can also be described based on two variables: length and tension. Together, these two filaments form myofibrils which are important organelles in the skeletal muscle system. Thin filaments are two strands of actin coiled around each, and thick filaments consist of mostly elongated proteins called myosin. įor the contractions to happen, the muscle cells must rely on the interaction of two types of filaments which are the thin and thick filaments. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. Muscle contraction is the activation of tension-generating sites within muscle cells.

Contractions of skeletal muscles allow vertebrate animals such as frogs to move

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