Week 5

Week 5

Skeletal Muscle
1. Structure
  1. 3 connective layers
    1. epimysium - outer
    2. perimysium - surrounds fascicle
    3. endomysium - inner
  2. fibres collect in bundles
  3. bundles group together along blood vessels
  4. fibre
    1. myofibrils
    2. sarcoplasm
    3. nuclei
    4. mitochondria
    5. capillary
    6. sarcolemma
    7. nerve
    8. satellite cell
      1. satellite cells are found under the basal lamina
      2. satellite cells are used for growth and regeneration
  5. multinucleated - 1 nucleus every 15 sarcomeres
  6. muscle cells fuse together to form 1 cell
  7. proliferating myoblasts are made in the body and move to the limbs during gestation
2. Sarcomeres
  1. structure
    1. I band - thin filament, Z disc
    2. A band - thick filament, M line
  2. contraction
    1. A band width does change
    2. I band width decreases
    3. thick and thin filaments slide past each other
  3. thick filament
    1. myosin
      1. 3 subunits
        sub 1 - motor domain, bind to nucleotides, bind to actin, 2 heavy chains
        sub 2 - 4 light chains, 2 essential, 2 regulatory
        light meromyosin - coiled coil, alpha helices, converge to form a thick filament
    2. each filament contains 294 molecules
    3. parallel and anti-parallel packing
    4. 14.3nm axial repeat
  4. thin filament
    1. actin
    2. fast growing end - barbed, negative, capping protein
    3. slow growing end - pointed, positive
    4. anchored to the Z disc
    5. cross linked to alpha-actinin
    6. tropomoldulin caps the pointed end to stop it growing
3. ATP Cycle
  1. ATP binds to myosin
  2. ATP is phosphorylated and binds to actin and it moves forward
  3. ADP detaches and the cycle starts again
4. Force of Movement
  1. depends on number of cross bridges
  2. depends on the amount of overlap
  3. zero force at overlap
  4. all sarcomeres contracting cause the muscle to contract
5. Tropomyosin & Troponin
  1. tropomyosin
    1. 2 long strands wrap around actin
    2. 1 for every actin subunits
    3. 3 subunits
      1. TnC - binds Ca
      2. TnL - inhibitory, binds to TnC, TnT and actin
      3. TnT - binds to tropomyosin
    4. how it works
      1. Ca binds to TnC
      2. TnL binds to TnC
      3. Myosin binding sites open
      4. Enter text here
Cardiac & Smooth Muscle
Mechanics of Muscle Contraction
Muscle Function During Locomotion

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