Myofibril: Difference between revisions
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The myofibril is a long contractile unit made of the [[Myofilaments|myofilaments]] [[Actin|actin]] and [[Myosin|myosin which]] form the [[Sarcomere|sarcomere]]. They line up parallel to one another forming cylindrical structures which bundle together into a muscle fibre. The regular arrangement of cross striations of sarcomeres, which can be observed under a low magnification [[Electron Microscopy|electron microscope]], attribute to the alternative name given to skeletal [[Muscle|muscles]]: striated muscle. An electron micrograph of myofibrils shows differently shaded bands. These are | The myofibril is a long contractile unit made of the [[Myofilaments|myofilaments]] [[Actin|actin]] and [[Myosin|myosin which]] form the [[Sarcomere|sarcomere]]. They line up parallel to one another forming cylindrical structures which bundle together into a [[Muscle fibres|muscle fibre]]. The regular arrangement of cross striations of sarcomeres, which can be observed under a low magnification [[Electron Microscopy|electron microscope]], attribute to the alternative name given to skeletal [[Muscle|muscles]]: striated muscle. An electron micrograph of myofibrils shows differently shaded bands. These are representative of the different density [[Protein|protein]] filaments: | ||
*Z lines: thick, darkly stained, short filaments which mark the start and end of the [[Sarcomere|sarcomere]]. They shorten during contraction. | |||
*A bands: thick, darkly stained region which marks the locations of myosin filaments and doesn’t change in length during contraction. | |||
*Z | |||
*A bands: thick, darkly stained region which marks the locations of myosin filaments. | |||
*M lines (or midlines): thin, darkly stained, short vertical filaments which link the two [[Myosin II complexes|myosin II complexes]] of the sarcomere at their tail regions. | *M lines (or midlines): thin, darkly stained, short vertical filaments which link the two [[Myosin II complexes|myosin II complexes]] of the sarcomere at their tail regions. | ||
*I bands: thin, lightly stained region which marks the locations of [[Actin filaments|actin filaments]] | *I bands: thin, lightly stained region which marks the locations of [[Actin filaments|actin filaments]]<ref name="Molecular Biology of The Cell">Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P. (2008) Molecular Biology of The Cell, 5th edition, New York: Garland Science</ref> and shortens during contraction. | ||
=== References === | === References === | ||
<references /> | <references /> | ||
Latest revision as of 19:33, 10 December 2018
The myofibril is a long contractile unit made of the myofilaments actin and myosin which form the sarcomere. They line up parallel to one another forming cylindrical structures which bundle together into a muscle fibre. The regular arrangement of cross striations of sarcomeres, which can be observed under a low magnification electron microscope, attribute to the alternative name given to skeletal muscles: striated muscle. An electron micrograph of myofibrils shows differently shaded bands. These are representative of the different density protein filaments:
- Z lines: thick, darkly stained, short filaments which mark the start and end of the sarcomere. They shorten during contraction.
- A bands: thick, darkly stained region which marks the locations of myosin filaments and doesn’t change in length during contraction.
- M lines (or midlines): thin, darkly stained, short vertical filaments which link the two myosin II complexes of the sarcomere at their tail regions.
- I bands: thin, lightly stained region which marks the locations of actin filaments[1] and shortens during contraction.
References
- ↑ Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P. (2008) Molecular Biology of The Cell, 5th edition, New York: Garland Science