Download - lec9[1]
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• Describe the characteristics & functions of muscle tissue.
• Describe organization of muscle tissue.
• Identify the components of the sarcomere.
• Identify components of the neuromuscular junction.
• Explain steps in skeletal muscle contraction.
• Relate microscopic function to macroscopic function.
Class 9Muscle Tissue- Anatomy& Contraction
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Muscle organization
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Formation of skeletal muscleMyoblast fusion
•Multinucleate
•Syncytial
satellite
T tubules
myofibril
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Myofilaments
Thick (myosin)
Thin (actin)
“Sliding filament hypothesis” vs. “Shortening filament hypothesis”
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Formation & membranesMyoblast fusion
•Multinucleate
•Syncytial
satellite
T tubules
myofibril
SR
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Sliding filaments
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Organization
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Actin & myosin
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Sliding filament theory
30% shorter
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Neural control
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Troponin blocks actin w/o Ca++
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Ca++ troponin to release actin
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Myosin head binds actin
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Myosin head turns, release ADP
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Pivoting causes shortening, ATP binding causes release
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ATP binds & loads myosin head
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Initial length & max. tension
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Overall lessons:• Muscle has many functions, principle of which is shortening.
• Muscles are made of fascicles of muscle fibers (cells).
• Muscles are covered and contain CT membranes w/ vessels & nerves.
• Muscle fibers are giant syncytial, multinucleate cells.
• Myofilaments are protein fibers that slide past each other to cause shortening.
• The S.R. stores Ca++, and releases Ca++ to facilitate cross-connections between the sliding filaments.
• The pattern of fiber connections is governed by mutually exclusive binding sites (troponin either Ca++ or actin; myosin either actin or ATP).
• Relaxation only possible by removing ACh & Ca++.