sarcomere

(noun)

The functional contractile unit of the myofibril of a striated muscle.

Related Terms

Examples of sarcomere in the following topics:

  • Sliding Filament Model of Contraction

    • In the sliding filament model, the thick and thin filaments pass each other, shortening the sarcomere.
    • To understand the sliding filament model requires an understanding of sarcomere structure.
    • A sarcomere is defined as the segment between two neighbouring, parallel Z-lines.
    • Titin molecules are thought to play a key role as a molecular ruler maintaining parallel alignment within the sarcomere.
    • The amount of force and movement generated generated by an individual sarcomere is small.

  • Skeletal Muscle Fibers

    • Skeletal muscles are composed of striated subunits called sarcomeres, which are composed of the myofilaments actin and myosin.
    • These proteins are organized into regions termed sarcomeres, the functional contractile region of the myocyte.
    • Within the sarcomere actin and myosin, myofilaments are interlaced with each other and slide over each other via the sliding filament model of contraction.
    • The regular organization of these sarcomeres gives skeletal and cardiac muscle their distinctive striated appearance.
    • The sarcomere is the functional contractile region of the myocyte, and defines the region of interaction between a set of thick and thin filaments.

  • Control of Muscle Tension

    • Neural control initiates the formation of actin–myosin cross-bridges, leading to the sarcomere shortening involved in muscle contraction .
    • Maximal tension occurs when thick and thin filaments overlap to the greatest degree within a sarcomere.
    • If a sarcomere at rest is stretched past an ideal resting length, thick and thin filaments do not overlap to the greatest degree so fewer cross-bridges can form.
    • As a sarcomere shortens, the zone of overlap reduces as the thin filaments reach the H zone, which is composed of myosin tails.
    • Conversely, if the sarcomere is stretched to the point at which thick and thin filaments do not overlap at all, no cross-bridges are formed and no tension is produced.

  • ATP and Muscle Contraction

    • Muscles contract in a repeated pattern of binding and releasing between the two thin and thick strands of the sarcomere.
    • When the actin is pulled approximately 10 nm toward the M-line, the sarcomere shortens and the muscle contracts.