VPB 121: Veterinary Physiology - II (2+1)

TYPE OF MUSCLE FIBRES

• FG cells have a
  • Shorter contraction time (5 – 50ms).
  • Less amt of myoglobin as FG cells go for anaerobic meth myoglobin with in the stage for O₂ is less needed.
  • Have more phosphorylase needed for degraded glycogen).
  • Larger cell diameters (fast twitching).
  • Fewer mitochondria (more numbers needed for aerobic metabolism).
  • More glycogen needed for anaerobic glycolysis.
  • Much less lipids (lipids are oxidized aerobically by β-oxidation).
  • Less blood flow.
  • Slower rate of protein turnover do not depend AA metabolism for energy.
  • Narrower Z disc 66 nm compared to 144 nm by SO cells – rapid contraction.
  • Fairly less red in colour (less myoglobin).
  • A more extensive and highly organized sarcotubular system (more Ca²⁺ storage for stronger contraction).
  • Less resistance to fatigue, and are innervated by large motor neurons,
  • Higher contractile speed (myosin dependant ATPase activity of FG fibers has 2 – 3 times more than SO fibers. FOG cells have intermediary characteristics between FG and SO cells. 2 disc width is 88 nm. Speed of contraction higher than SO but lower than FG, have shorter contraction periods.