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The Muscular System

The Muscular System. Ch. 10-11. Organization of Muscle fibers. Muscle fibers in skeletal muscle form bundles: fascicles 4 main muscle types: based off of fascicle shapes Parallel Convergent Pennate Circular . Parallel Muscles. Fascicles run parallel

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The Muscular System

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  1. The Muscular System Ch. 10-11

  2. Organization of Muscle fibers • Muscle fibers in skeletal muscle form bundles: fascicles • 4 main muscle types: based off of fascicle shapes • Parallel • Convergent • Pennate • Circular

  3. Parallel Muscles • Fascicles run parallel • Tapered ends with broad mid-section • Example: biceps brachii

  4. Convergent Muscles • Fascicles are spread over broad area • All fibers taper together at one attachment site • Example: pectoralis

  5. Pennate Muscles • Fascicles form a common angle with a tendon • 2 types: • Unipennate • Example: extensor digitorum • Bipennate • Example: rectus femoris

  6. Circular Muscles • Fascicles form concentrically around an opening • Also known as sphincter • Change the diameter of the opening • Example: Orbicularis Oris

  7. Anatomy of Skeletal Muscle • 3 Layers of tissue in each muscle • Epimysium • Surrounds the muscle, separates it from surrounding tissues • Perimysium • Divide skeletal muscle into compartments, called fascicles • Contains blood vessels and nerves • Endomysium • Within each fascicle • Surrounds individual muscle fibers • At each end where the 3 layers come together form a bundle known as a tendon---attach muscle to bones.

  8. Day 2

  9. Micro-anatomy of Muscle tissueSkeletal Muscle bundle (covered by Epimysium) Many Muscle Fascicles (covered by perimysium) Many Muscle Fibers (covered by endomysium)  Many Myofibrils  Many Sarcomeres Many Actin and Myosin Filaments

  10. Myofibril & Sarcomere

  11. I Band (Thin Filaments) • Actin • A Band (Thick Filaments) • Myosin

  12. Muscle Contraction Terms • Tropomyosin (2 stranded, prevents actin-myosin interaction) • Troponin (protein, allows actin-myosin interaction by binding tropomyosin) • Ca++ ions bond to troponin molecule, tropomyosin changes, exposing active site of actin, thus allowing myosin to interact with actin, and initiating contraction.

  13. Videos • Muscle Structure

  14. Sliding Filament Theory(Contraction Cycle ) • 1. Exposure of Active Sites (Ca++ ions bind with troponin, pulling tropomyosin away from actin) • 2. Attachment of cross-bridges (myosin binds with actin) • 3. Pivoting of myosin heads (contraction) • 4. Detachment of cross-bridges (ATP breaks connection, so another attachment can be made-continuing contraction) • 5. Reactivation of myosin (Myosin head splits ATP into ADP and P, energy released “recocks” myosin head so cycle can be repeated.

  15. Rigor Mortis • Ca++ keeps pumping in, but no ATP is available to “recock” or pump Ca++ ions out. • Without ATP, cross bridges cannot detach from the active sites. • “Stiff as a board”

  16. Energy Use • It takes a lot of ATP to sustain muscle contraction • Muscles store enough to start a contraction • To continue a contraction, ATP must be made by the muscle fiber with the help of creatine phosphate.

  17. Aerobic Metabolism • Creates 17 ATP for every unit “fed” into it. (fatty acids) • 95% of energy for resting muscles • Happens in mitochondria

  18. Anaerobic Glycolysis • Creates 2 ATP/ glucose • Primary source during peak muscle activity • Lack of available oxygen • Happens in cytoplasm • Produces lactic acid • Lowers pH of blood • Can stop muscle contraction • But, once oxygen is available again, mitochondrial activity resumes, lactic acid is carried through blood to liver and converted back to glucose

  19. Muscle Fatigue and Recovery • Muscle Fatique=cannot perform anymore • WHY: Muscle function requires: • Substantial intracellular energy reserves • Normal circulatory supply • Normal blood oxygen concentrations • Heat loss-because only about 30% of released energy is captured at ATP-the rest is lost as heat.

  20. Muscle Fibers • Fast Twitch Fibers (White muscle) • Contract quickly and powerfully • Few mitochondria • Fatigue quickly • Slow Twitch Fibers (red muscle) • Contract slowly • Slow to fatigue • More mitochondria

  21. What you don’t use, You’ll loose. • Skeletal muscles become smaller in diameter • Decreased blood supply • Smaller ATP • Skeletal muscles become less elastic • Increasing fibrous tissue • Tolerance decreases • Cannot eliminate heat generated • Fatigue greater • Ability to recover from injury decreases • Less tissues in muscle to help heal

  22. Muscle Decline • The rate of decline is the same in all people regardless of exercise patterns • Therefore, to be in good shape later in life; you have to be in good shape earlier in life.

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