1' dia

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HISTOLOGY 1.12 MOLECULAR BASIS OF
CROSS-STRIATION AND MUSCLE CONTRACTION
LM micrographs of striated muscle Low power EM
micrograph High power EM micrograph
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Structure of the myofibrils
Sarcomer 2,2-2,5 mm
Myofilaments Thick (myosin) Thin (actin)
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Myofilaments 1. The thin filament
6-9 nm
F-actin (made up by several G-actins)
Further proteins involved
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Myofilaments 2. The thick filament
Building block the myosin molecule
L-chains
H-chains
Heads
Arrangement of the myosin molecules within the
filament (250-350 molecule/filament)
Bipolar structure
Myosin heads
12- 15 nm
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The sliding filament mechanism of the
contraction
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Cytoskeletal proteins within the sarcomer
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The sarcoplasmic reticulum and the transverse
tubular system (T-system)
Sarcoplasmic reticulum Longitudinal
tubules Terminal cisterns
triads
Triad T-tubule two adjacent terminal cisterns
of the sarcoplasmic reticulum