The Sarcomere. A sarcomere is a contractile unit of skeleton muscle that is separated into I and A bands, M and Z lines, and H zone.

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Key Points

• A sarcomere is the basic contractile unit of skeletal muscle the is make of thick and thin filaments.

• Thick filaments are arranged bundles of myosin, while thin filaments room made of actin along with the two various other regulatory proteins-troponin and also tropomyosin.

• Z-lines define the borders of every sarcomere.

• The M-line runs down the facility of the sarcomere, through the center of the myosin filaments.

• The I-band is the an ar containing only thin filaments.

• The H-zone contains only thick filaments.

• The A-band contains both thick and also thin filaments and also is the center of the sarcomere the spans the H zone.

• When the muscle contracts, the H-zone, I-band, the distance between Z-lines all come to be smaller, vice versa, the A band continues to be the same.

Key Terms

Sarcomere: The functional unit of the skeleton muscle.

Thin filament/actin: A protein that creates (together with myosin) the contractile filaments that muscle cells, and also is likewise involved in motion in other types of cells.

Thick filament/myosin: A fibrous protein that develops (together v actin) the contractile filaments that muscle cells and is likewise involved in movement in other types of cells.

Troponin: A complicated of three regulatory proteins that is integral come muscle convulsion in skeletal and cardiac muscle, or any kind of member the this complex.

Tropomyosin: A protein associated in bones muscle contraction and that wraps roughly actin and prevents myosin from grabbing it.

I-band: The area nearby to the Z-line, wherein actin is no superimposed by myosin.

A-band: The length of a myosin in ~ a sarcomere.

M-line: The heat at the center of a sarcomere to which myosin bind.

Z-line: Neighboring, parallel present that define a sarcomere.

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H-band: the area surrounding to the M-line, where myosin is not superimposed by actin.