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  • 1. Internal structure of skeletal muscle
    Nucleus: Contain the genetic material of the cell
    Sarcolemma: Plasma membrane of muscle cell
    T Tubule: Invagination of the Sarcolemma project deep into Muscle cells interior
    Terminal cisternae: Serve as specialized reservoirs for Ca ions
    Myofibril: Bundle of contractile filaments
  • 2. The myofibrils composed of individual contractile proteins called myofilaments
    There are two types of myofilaments:
    Thin filaments composed mainly of protein Actins
    The thick filaments is composed mainly of protein myosin
    Structure of Myofibrils
  • 3. Organization levels of skeletal muscle
    Myofilaments: Smallest building blocks. Compose of thick and thin
    Myofibril: Many myofilaments bundle together making a single myofibril
    Muscle cell: Many myofibril are contained within the muscle cell
    Fascicle: Many muscle cells are packed into a fascicle
    Muscle: Many fascicle make up the muscle
  • 4. The Sliding Filament
    Sliding filament occurs as a thin filaments slide past the thick filament. This involve the activity of:
    Myocin
    Actin
    Tropomyosin
    Troponin
    ATP
    Ca ions
  • 5. The Thick Filament (Myosin)
    Consists of the protein called myosin.
    A myosin molecule is shaped a bit like a golf club, but with 2 heads.
    The heads stick out to form the cross bridge
    Many of these myosin molecules stick together to form a thick filament
    Each head contains two binding sites, one for actin and one for ATP.
  • 6. Thin Filament (Actin)
    The thin filament consists of a protein called actin. It compose of actin subunit twisted into double helical chain. Actin has specific binding site to which the myosin head binds
    The thin filament also contains tropomyosin. The position of tropomyosin cover the binding sites on the actin during unstimulated muscle
    The third component is troponin. Attached along the tropomyosin strand.Which expose the binding site of actin to myosin
  • 7. Arrangement of Myofilament
    The arrangement of thick and thin myofilaments forms light and dark alternating bands (striation).
    In the middle of the light band is the Z-line
    The repeating unit from one Z-line to the next is called the sarcomere
  • 8. I Band = actin filaments
  • 9. Ca Ion
    After action potential, Ca ions released from the T-Tubules and bind to troponin. This causes change in conformation of the troponin – tropomyosin complex and thus dragging tropomyosin strands off the binding site
  • 10. Sliding-Filament Mechanism
  • 11. Sliding-Filament Mechanism
  • 12. Sliding-Filament Mechanism
  • 13. Sliding-Filament Mechanism
  • 14. Sliding-Filament Mechanism
  • 15. Steps of cross bridge cycle
    The influx of Ca ion, triggering the exposure of binding sites on actin
    The binding of myosin to actin
    The myosin cross bridge pulls the thin filament inward toward the centre of sarcomere
    The binding of ATP to the myosin head disconnecting from actin
    The hydrolysis of ATP leads to repositioning of the myosin head
    The transport of Ca ion to the back into the sarcoplasmic reticulum