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Muscle Structure and Function

This guide delves into the complexities of muscle biology, focusing on the structure and function of skeletal, smooth, and cardiac muscles. It covers essential topics such as major muscle groups, histology, gross and microscopic anatomy, the sliding filament model of contraction, and the biochemical processes underlying muscle contraction. Additionally, it explains the role of neuromuscular junctions, action potentials, and energy production pathways, including aerobic and anaerobic respiration, crucial for muscle metabolism.

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Muscle Structure and Function

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  1. Muscle Structure and Function Biology 2121 Chapters 9-10

  2. Introduction 1. Functions • Movement, Posture; Heat and Joints 2. Naming (321) • Location; Shape (temporalis; deltoid) • Size (gluteus maximus) • Fiber Direction (abdominus rectus) • Origins (bicep) • Location of Attachment (sternocleidomastoid)

  3. Major Muscle Groups Chest and Shoulder Group Abdominals Quadriceps and Hamstring Group

  4. Histology of Muscle Tissue- Skeletal Muscle • Voluntary • Found in major muscle groups • Striated • Multinucleated • Peripheral

  5. Smooth Muscle • Involuntary • Found in digestive system organs, bladder, etc. • Non-Striated • Uninucleated • Spindle-Shaped nuclei

  6. Cardiac Muscle • Involuntary • Heart only • Branching Fibers • Uni-Nucleated

  7. Gross Anatomy • 1. Wholemuscle • Epimysium • 2. Fascicles • Perimysium • 3. MuscleFiberCells • Long and multi-nucleated • Sarcolemma and sarcoplasma • Endomysium

  8. Attachments • Tendons • Aponeurosis • Direct or Indirect Attachments

  9. Microscopic Anatomy – Myofibrils • 1. Contractileproteins • 2. Sarcomeres • Actin and myosin • 3. Myofilaments • Actin(thin) • Myosin (thick)

  10. Sarcomere • 1. A ‘sarcomere’ • Z to Z • I-Band (light zone) • A-Band (dark zone) • 2. StructuralProteins • Elastic filaments – Titan • 3. SlidingFilamentModelof Contraction • Link

  11. Sarcomere Contraction

  12. Chemical Stimulation and Muscle Contractions • 1. Stimulation and Neurotransmitters • Acetylcholine • 2. NeuromuscularJunction • Junction – muscle/nerve interface • Separation – “synapse”

  13. Neuromuscular Junction

  14. Events at the Neuromuscular Junction • 1. Nerve Impulse • 2. Calcium ions – Axon Terminal of Nerve • 3. Vesicle and release of ACh • 4. ACh receptors and Acetylcholinesterase • 5. Sodium-Potassium exchange • 6. Action Potential formed

  15. Neuromuscular Junction

  16. Action Potential • 1. RestingMembrane • -70 mV • Na+ and K+ • 2. Reversalof Charges • Depolarization • 3. Movesin oneDirection

  17. What Happens after the Action Potential is Formed?

  18. Excitation and Contraction • 1. ActionPotential moves along the sarcolemma • 2. Down the T-Tubule • 3. SarcoplasmicReticulum and Release of Ca++ • 4. Ca++ moves to the sarcomere

  19. Formation of a Cross-Bridge • 1. Ca++ interacts with troponin • 2. Removestropomyosin • 3. Allows for MyosinHeadAttachment • 4. Formation of a cross-bridge

  20. Cross-Bridge Cycling • 1. Myosinheadsattach forming cross- bridge • 2. WorkingStroke • 3. ATPbreaks cross- bridge • 4. ATPhydrolysis • 5. High-energy configuration – New Cross-bridge

  21. ATP and Muscle Metabolism ATP Functions – Driving Cellular Work

  22. ATP Production 1. CreatinePhosphate – Quick and Fast!!! 2. AnaerobicRespiration • “Lactic Acid Fermentation” • 1 glucose molecule = 2 ATP Net 3. AerobicRespiration • 1 glucose molecule = 36 ATP Net • Mitochondria of the Cell

  23. Aerobic Respiration

  24. Fermentation • Glycolysis • (2) Pyruvicacidmolecules (3-C) • Bloodflowrestrictedduring vigorous exercise (low oxygen) • Lacticacidformed • Anaerobic glycolysis

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