Myofibril

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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 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 representitive of the different density [[Protein|protein]] filaments:<br>
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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 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.
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*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.
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*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|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]]&nbsp;<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>&nbsp;and shortens during contraction.
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*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 />

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:

References

  1. 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
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