Sarcomere
Smallest functional unit of striated muscle tissue.
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User:Sameerb · via Wikipedia: Sarcomere · Copyrighted free use
It is the repeating unit that gives skeletal and cardiac muscle their striated appearance, first described by Van Leeuwenhoek.[1] In striated muscle tissue, the repeating unit that lies between two Z-lines is known as a sarcomere, which constitutes the smallest functional unit.[2][1] The Z-line, which delineates the sarcomere's boundaries, has actin molecules attached to it.[3]
Key facts and history
The sarcomere's striated appearance was first described by Van Leeuwenhoek.[1] Thin filaments, composed of actin, are primarily located in the I-band and also project into the A-band.[3] Thick filaments, made of myosin, are bipolar in shape and run the entire length of the A-band.[3] Titin, the largest highly elastic protein known in nature, spans from the Z-line to the M-band.[3]
Titin is believed to serve as a sarcomeric ruler and offers attachment points for many different proteins.[3] Nebulin, another large protein, is thought to run the length of the I-band alongside the thin filaments.[3] Within the Z-disc, the protein alpha-actinin creates cross-links between actin filaments and titin molecules.[3] Muscle contraction, explained by the sliding filament model, results from the interaction of actin and myosin filaments within the A-band.[3]
What the research sources say
The Open Library record for ISBN 0805366245 lists "Biology, Sixth Edition" as a 1175-page book published by Benjamin Cummings on December 11, 2001.[4] The Open Library record for ISBN 9780781730617 lists "Skeletal Muscle Structure, Function, and Plasticity" as a 448-page book published by Lippincott Williams & Wilkins on July 15, 2002.[5]
References
- Wikipedia, "Sarcomere" (CC BY-SA 4.0), which cites: "Biology", Benjamin Cummings, 2002; Martonosi, "Animal electricity, Ca2+ and muscle contraction. A brief history of muscle research", Acta Biochimica Polonica, 2000-01-01, p. 493–516 (we also read that source) en.wikipedia.org
- Wikipedia, "Sarcomere" (CC BY-SA 4.0), which cites: Biga, "10.2 Skeletal Muscle", Anatomy & Physiology, 2019 (original not read by us) en.wikipedia.org
- Wikipedia, "Sarcomere" (CC BY-SA 4.0), which cites: "Biology", Benjamin Cummings, 2002 (we also read that source) en.wikipedia.org
- Open Library record, ISBN 0805366245 ("Biology, Sixth Edition"). CC0 (metadata); book content not read. openlibrary.org
- Open Library record, ISBN 9780781730617 ("Skeletal Muscle Structure, Function, and Plasticity"). CC0 (metadata); book content not read. openlibrary.org
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Sarcomere (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Sarcomere (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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