Chap 8_Skeletal Muscle_Structure and Control of Movement.pptx - Skeletal Muscle Structure and Function Longitudinal section of skeletal muscle Lecture

Chap 8_Skeletal Muscle_Structure and Control of Movement.pptx

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Skeletal Muscle: Structure and Function Longitudinal section of skeletal muscle
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Lecture Objectives 1. Draw and label the microstructure of skeletal muscle 2. Define satellite cells. How do these cells differ from the nuclei located within skeletal muscle fibers? 3. List the chain of events that occur during muscular contraction 4. Describe what causes a muscle cramp
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Brief Introduction to Skeletal Muscle Human body contains over 600 skeletal muscles 40-50% of total body weight Functions of skeletal muscle 1) 2) 3) Structure of Skeletal Muscle
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Connective Tissue Sheaths
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Discussion Question Why is it important to understand the connective tissue sheaths?
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Microanatomy of Skeletal Muscle “Multi-nucleated” “Long cylindrical cells” Contractile element “Distinctive feature”
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Microstructure of Muscle Fibers Myofibrils Contain contractile proteins Actin (thin filament) Myosin (thick filament) Sarcomere Includes Z line, M line, H zone, A band, I band Sarcoplasmic reticulum Longitudinal network of tubes that wrap around myofibrils Storage sites for calcium Transverse tubules Extend from sarcolemma to sarcoplasmic reticulum Deliver neural stimulus to contractile proteins Structure of Skeletal Muscle
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Microstructure of Myofibril Structure of Skeletal Muscle
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Satellite Cells Play role in muscle growth and repair Increase number of nuclei Myonuclear domain: Cytoplasm surrounding each nucleus Each nucleus can support a limited myonuclear domain More nuclei allow for greater protein synthesis Important for adaptations to ____________________ Structure of Skeletal Muscle
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A Sarcomere— The Functional Unit of the Myofibril Dark region Light region
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Myosin and Actin Filaments - Striations “Thick filament”: Myosin head and tail “Thin filament”: Anchored to Z line Tube-shape protein, twists around actin Protein attached at regular intervals
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Neuromuscular Junction Junction between motor neuron and muscle fiber Motor end plate : Pocket formed around motor neuron by sarcolemma Neuromuscular cleft : Short gap between neuron and muscle fiber Acetylcholine is released from the motor neuron Causes an end-plate potential (EPP) Depolarization of muscle fiber Neuromuscular Junction
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The Neuromuscular Junction Neuromuscular Junction
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The Sliding Filament Model Muscle shortening occurs due to the movement of the actin filament over the myosin filament Formation of cross-bridges between actin and myosin filaments Power stroke Reduction in the distance between Z lines of the sarcomere Muscular Contraction
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Sliding Filament Model Myosin head attaches to actin Myosin head bends to move actin “Slides toward M line” Expend energy to create movement ATP acts to unhook myosin
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Relaxed Sarcomere Relaxed when myosin + actin are slightly overlapped
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Partially Contracted Partially contracted when there is more overlap between myosin + actin I band gets shorter
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Fully Contracted I band has disappeared Fully contracted when myosin + actin are completely overlapped
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Sarcomere Shortening During Muscle Contraction Muscular Contraction
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