Sarcoplasm
Sarcoplasm shown with a muscle fiber
Details
LocationCytoplasm of muscle cell
Identifiers
Latinsarcoplasma
THH2.00.05.0.00004
Anatomical terms of microanatomy

Sarcoplasm is the cytoplasm of a muscle cell. It is comparable to the cytoplasm of other cells, but it contains unusually large amounts of glycogen (a polymer of glucose), myoglobin, a red-colored protein necessary for binding oxygen molecules that diffuse into muscle fibers, and mitochondria.[1][2][3] The calcium ion concentration in sarcoplasma is also a special element of the muscle fiber; it is the means by which muscle contractions take place and are regulated.[4][5] The sarcoplasm plays a critical role in muscle contraction as an increase in Ca2+ concentration in the sarcoplasm begins the process of filament sliding. A decrease in Ca2+ in the sarcoplasm subsequently ceases filament sliding.[6] The sarcoplasm also aids in pH and ion balance within muscle cells.[3]

It contains mostly myofibrils (which are composed of sarcomeres), but its contents are otherwise comparable to those of the cytoplasm of other cells. It has a Golgi apparatus near the nucleus, mitochondria just inside the cell membrane (sarcolemma), and a smooth endoplasmic reticulum (specialized for muscle function and called the sarcoplasmic reticulum).[7]

While sarcoplasm and myoplasm, viewed etymologically, might seem to be synonyms, they are not. Whereas sarcoplasm is a type of cytoplasm, myoplasm is the entire contractile portion of muscle tissue.[4][5][7]

While some authors argue that the proteins and other molecules within the sarcoplasmic reticulum lumen technically belong to the sarcoplasm. These molecules aren't part of the sarcoplasmic reticulum membrane itself but reside within the enclosed sarcoplasmic reticulum space. In that sense, one could say the sarcoplasmic reticulum has a type of specialized sarcoplasm.

References

  1. ↑ Douplik, A (2013) The response of tissue to laser light. Woodhead Publishing. pp. 47–109. ISBN 978-0-85709-237-3.
  2. ↑ Toumanidou, Themis (2018). Chapter 9 - Spinal Muscles. Academic Press. pp. 141–166. ISBN 978-0-12-812851-0.
  3. 1 2 Roberts, Michael D.; Haun, Cody T.; Vann, Christopher G.; Osburn, Shelby C.; Young, Kaelin C. (2020). "Sarcoplasmic Hypertrophy in Skeletal Muscle: A Scientific "Unicorn" or Resistance Training Adaptation?". Frontiers in Physiology. 11. doi:10.3389/fphys.2020.00816. ISSN 1664-042X. PMC 7372125. PMID 32760293.
  4. 1 2 Mescher, Anthony L. (22 February 2013). Junqueira's basic histology : text and atlas. Junqueira, Luiz Carlos Uchôa, 1920- (Thirteenth ed.). New York. ISBN 978-0-07-180720-3. OCLC 854567882.{{cite book}}: CS1 maint: location missing publisher (link)
  5. 1 2 Ross, Michael H. (2011). Histology : a text and atlas : with correlated cell and molecular biology. Pawlina, Wojciech. (6th ed.). Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health. ISBN 978-0-7817-7200-6. OCLC 548651322.
  6. ↑ Shahinpoor, Mohsen (2013). Muscular Biomimicry. Elsevier. pp. 139–160. ISBN 978-0-12-415995-2.
  7. 1 2 Trovato, Francesca Maria; Imbesi, Rosa; Conway, Nerys; Castrogiovanni, Paola (22 July 2016). "Morphological and Functional Aspects of Human Skeletal Muscle". Journal of Functional Morphology and Kinesiology. 1 (3): 289–302. doi:10.3390/jfmk1030289.
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