myofibrils

• myofibrils overview

  • located in the sarcoplasm
  • 2 types of protein filaments=myosin and actin
  • myosin and actin make up a sarcomere
• sarcomere

  section of myofibril between 2 Z lines

  • H band=only myosin
  • I band= only actin
  • M band= attachment for myosin
  • A band= areas where only myosin and areas where myosin and actin overlap
  • Z line=attachment for actin
• thick filaments

  • made up of myosin molecules
  • fibrous protein molecules with a globular head
  • fibrous part anchors molecules into thick filament
  • in filament-myosin molecules lie next to eachother(globular head facing away from M line)
• thin filaments

  • made up of actin molecules
  • globular protein molecules
  • 2 actin chaisn twist to form 1 thin actin filament
  • tropomyosin twisted around the 2 chains
  • troponin attached to chain at regular intervals