3A. Musculo skeletal system

• Motor unit: A motor neuron along with muscle fibre innervated by its teledendrites is called a motor unit
• Triad System:

  • Each T tubule is flanked on either side by several terminal cisternae of the sarcoplasmic reticulum
  • The T tubule and the two terminal cisternae at its sides form the triad system
• Difference between actin and myosin:

  Actin:

  • Actin is a thin contractile protein
  • Actin is present in the light band called the isotropic band
  • Actin filaments are connected to the Z line

  Myosin:

  • Myosin is a thick contractile protein
  • Myosin is present in dark bands called anisotropic band
  • Myosin filaments are connected to the M line
• Distinguish between red muscle fibers and white muscle fibers:

  White muscle fibers:

  • Have less quantity of myoglobin and very few mitochondria
  • They are called anaerobic muscles
  • They depend on anaerobic process for release of energy

  Red muscle fibers:

  • Have more myoglobin and more mitochondria
  • They are called aerobic muscles
  • They utilize oxygen stored in mitochondria