Sliding filament theory


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Sliding filament theory

  1. 1. How Muscles Contract Sliding Filament Theory Lloyd Dean
  2. 2. Recap: Let’s do it again! Team “Oxy” Team “FOG” Team “Bolt” Walk around the 12 press ups Every 10 seconds perform an explosive activity room until told otherwise 1:1 3:1 I shall pick the music! 10:1
  3. 3. SUMMARY OF SKELETAL MUSCLE FIBER TYPES Slow oxidative fibers Myoglobin content Mitochondrial Density Filament organization Type of respiration Speed of contraction Duration of contraction Resistance to fatigue Twitch Function Fast oxidativeglycolytic fibers Fast glycolytic fibers
  4. 4. SUMMARY OF SKELETAL MUSCLE FIBER TYPES Slow oxidative fibers Fast oxidativeglycolytic fibers Fast glycolytic fibers Myoglobin content High High Low Mitochondrial Density Highest Moderate Lowest Filament organization Striated Striated Striated Type of respiration Aerobic Aerobic and anaerobic Glycolysis Speed of contraction Slow Fast Fast and strong Duration of contraction Long Brief Short Resistance to fatigue High Moderate Low Twitch Slow twitch Fast twitch Fast twitch Function Endurance activities e.g., running a marathon Short periods of intense activity Activities such as sprinting or e.g., strength training or throwing walking uch as sprinting or a javelin walking
  5. 5. Aims By the end of the lesson you should be able to: Describe the sliding filament theory Explain the microstructure of muscle State the all or nothing law
  6. 6. Look at the start Look at the end Sliding Filament Theory
  7. 7. Structure of Skeletal Muscle Epimysium Surrounds entire muscle Merges into tendon that is composed of tough collagen Perimysium Surrounds bundles of muscle fibers Endomysium Surrounds individual muscle fibers Lets make our own!
  8. 8. Structure of Skeletal Muscle: Microstructure Sarcolemma Muscle cell membrane Myofibrils Threadlike strands within muscle fibers Actin (thin filament)  Troponin  Tropomyosin Myosin (thick filament) “Sarco” means flesh “Lemma” means husk (Outer layer) Further divisions of Myofibrils “Myo” is muscle Z-line A-band I-band Sarcoplasm Sarcoplasmic reticulum  Storage sites for calcium  Surrounds myofibrils Transverse tubules
  9. 9. Muscular Contraction The sliding filament model (Hugh Huxley, 1954) Muscle shortening occurs due to the movement of the actin filament over the myosin filament Reduction in the distance between Z-lines of the Sarcomere Lets see a preview before the play………..
  10. 10. Sliding Filament Theory: A Love Story Winner of 2 Golden Globes and 3 Oscar’s. Directed by Lloyd Dean and his award winning students The background Actin and Myosin are in deeply in love and wish to live a happy life together and stay in full muscle contraction. The nasty Tropomyosin has other idea’s……. Let’s see the cast……..
  11. 11. A bit of inspiration!
  12. 12. Cast (Check out by clicking this link)  Nervous Impulse – The brain “Polices” the body. It sends a “Message” and “S.O.S” to muscle which helps it to contract!  Acetylcholine – A “Help!”ing horming  Calcium – Calcium “Ion”. A bit like a “Lion in Zion”  Tropomyosin – Doesn’t want Actin and Myosin to become attached. Scary!  Troponin – Actin and Myosin “Lean on” “Glee”fully to help remove tropomyosin  Actin and Myosin – “Montague & Capulets” protein filament families  ATP – An energetic friend  Now to the chapters of our story....
  13. 13. Chapters 1. A Milky Message 2. Two Forces Join 3. A Tiresome Pull 4. Powering Through 5. A Milky Removal We need to build this story together! You will be involved with the delivery of a chapter Know what’s going through We will make an iMovie!
  14. 14. A Milky Message Nerve Impulse sent to neuromuscular junction (Place where the brain and muscle communicate) Hormone (Acetylcholine) diffuses This causes calcium ions to be released in the sarcoplasmic reticulum (Surrounds myofibrils)
  15. 15. Two Forces Join Calcium ions join with troponin Causes tropomyosin to be removed from actin Actin and myosin join together
  16. 16. A Tiresome Pull Actin and myosin are now joined Myosin pulls actin inwards slightly ATP enables quick detachment of actin and myosin in preparation for power stroke
  17. 17. Powering Through ATP is broken down This enables Myosin to powerfully pull actin inwards Sarcomere and distance between Z discs shortens This process continues at a high rate and as long as there are calcium ions present
  18. 18. A Milky Removal Once impulse stops.... Calcium Ions are sent back to sarcoplasmic reticulum Tropomyosin rejoins actin Sarcomere and Z disc distance increase Muscle is relaxed
  19. 19. Look at the start Look at the end Sliding Filament Theory
  20. 20. All or None Law Fiber contracts completely or not at all