skeletal muscle microscopic anatomy chapter 10. microscopic anatomy muscle fibers = muscle cells:...
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Skeletal Muscle Microscopic
AnatomyChapter 10
Microscopic Anatomy
• Muscle fibers = muscle cells: long and multinucleate
• Sarcolemma: cell membrane
• Sarcoplasm: cytoplasm; rich in oxygen-storing myoglobinmyoglobin protein
• Myofibrils: bundles of contractile proteins; fill most of the cytoplasm; 100’s to 1000’s per cell
• Sarcomeres: the repeating functional unit of contraction in each myofibril
• Sarcoplasmic reticulum (smooth ER): stores Ca+
+ (muscle contraction begins when stored Ca++ ions are released into sarcoplasm)
• Mitochondria: provide ATP for contraction
•T tubules (transverse tubules): narrow tubes that are continuous with sarcolemma, conduct impulses
Closer Look at Myofibril Composition
• thin filaments: actin (plus tropomyosin & troponin)
• thick filaments: myosin
Fig. 10.5
Sarcomere Structure
• Z lines: the boundary between sarcomeressarcomeres
• A band: overlap of thick (myosin) filaments & thin (actin) filaments
• I band: thin (actin) filaments only
• H zone: thick (myosin) filaments only
Fig. 10.3
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