Slow/Fast twitch

• What are skeletal muscles made up of?


  2 types of muscle fibres - slow twitch and fast twitch
• Different muscles have what?

  different proportions of slow and fast twitch fibres
• DESCRIBE SLOW twitch muscle fibres?


  muscle fibres that contract slowly
• Describe fast twitch muscle fibres?


  Muscle fibres that contract very quickly
• What do you use slow twitch muscle fibres for?


  posture eg those in back, have a high proportion of them
• what do you use fasttwitch muscle fibres for?


  fast movement

  • eg those in eyes and legs, have a high proportion of them
• What are slowtwitch muscle fibres good for?


  endurance activities eg maintaining posture, long-distance running
• What are fast twitch muscle fibres good for?


  Short bursts of speed and power

  • eg eye movement
  • eg sprinting
• How long can slow twitch muscle fibres work for?


  A long time without getting tired
• How long can fast twitch muscle fibres work for?


  get tired very quickly
• How is energy released - slow twitch muscle fibres?


  Energy is released slowly through aerobic respiration

  • lots of MITOCHONDRIA and BLOOD VESSELS supply the muscles with OXYGEN
• How is energy released- fast twitch muscle fibres?


  Energy is released QUICKLY through ANAEROBIC respiration using GLYCOGEN (stored glucose)

  • there are FEW mitochondria or blood vessels
• What colour are slow twitch muscle fibres?


  Reddish in colour

  • because they are rich in myoglobin (a red-coloured protein that stores oxygen)
• What colour are fast twitch muscle fibres?


  Whitish in colour because they do not have much MYOGLOBIN (so cannot store much oxygen)