Muscle Fibres

• What is the skeletal muscle made up of?

  Large bundles of long cells, called muscle fibres
• What is the SARCOLEMMA?


  The cell membrane of muscle fibre
• What do bits of the sarcolemma do?


  Fold inwards across the muscle fibre and stick into the sarcoplasm

  • these folds are called TRANSVERSE (T) TUBULES - they help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre
• What is the sarcoplasm?


  a muscle cell's cytoplasm
• What is the sarcoplasmic reticulum?


  A network of internal membranes

  • runs through the sarcoplasm
• What does the sarcoplasmic reticulum do?


  Stores and releases calcium ions that are needed for muscle contraction
• What do muscle fibres have lots of and why?


  Lots of mitochondria

  • to provide the ATP that is needed for muscle contraction
• Muscle fibres are what?


  Multinucleate

  • (contain many nuclei)
• What do muscle fibres have lots of?


  Long, cylindrical organelles called MYOFIBRILS
• what are myofibrils made of ?


  proteins
• What are myofibrils highly specialised for?


  contraction