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