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Structure of Skeletal Muscle. Presentation by: Angela Holloman. Introduction . All activities that involve movement depend on muscles 650 muscles in the human body Various purposes for muscles for: Locomotion Upright posture Balancing on two legs Support of internal organs

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structure of skeletal muscle

Structure of Skeletal Muscle

Presentation by: Angela Holloman

introduction
Introduction
  • Allactivities that involve movement depend on muscles
  • 650 muscles in the human body
  • Various purposes for muscles for:
    • Locomotion
    • Upright posture
    • Balancing on two legs
    • Support of internal organs
    • Controlling valves and body openings
    • Production of heat
    • Movement of materials along internal tubes
  • Three types of muscles in the human body
    • Skeletal
    • Cardiac
    • Smooth
skeletal muscle
Skeletal Muscle
  • Skeletal muscles are muscles which are attached to the skeleton.
  • 40% of human body mass
  • Skeletal muscles are mainly responsible for locomotion, and voluntarycontraction and relaxation.
structure of skeletal muscles
Structure of Skeletal muscles
  • Skeletal muscles are composed of clusters of muscle cells.
    • Muscle fibers
    • Myofibers
    • Myocytes
  • A muscle consists of packages of muscle cells called fascicles
  • A muscle cell is long and spindle shaped
structure of skeletal muscles5
Structure of Skeletal muscles
  • Cell structure
    • Muscles cells contain many nuclei
    • The plasma membrane→ sarcolemma
    • The cytoplasm→ sarcoplasm
    • Length
        • ranges from 0.1cm to more the 30cm in length
    • Diameter
        • ranges from 0.001cm to 0.01cm in diameter
  • Myofibrils→
    • elongated protein molecules
    • aligned in parallel arrangements
    • extend the full length of the cell.
structure of skeletal muscles8
Structure of Skeletal muscles
  • The myofibril consists of protein chains called myofilaments
    • Myofilaments have a symmetrical, alternating pattern of thick and thin elements.
skeletal muscle myosin
Skeletal Muscle Myosin
  • Thick myofilament
  • consists of a large number of bundled myosin molecules aligned in overlapping arrays.
  • hexameric proteins with two identical heavy chains and two pairs of different light chains.
    • regulatory light chain (RLC)
    • essential light chain (ELC)
skeletal muscle actin
Skeletal Muscle Actin
  • The thin myofilament (F-actin, filamentous actin)
    • made up of two helically intertwined chains of G-actin (globular actin) units.
  • Other proteins that bind to the actin molecules:
      • Tropomyosin
      • The Troponin complex→ made up of three members
contraction of skeletal muscle
Contraction of Skeletal Muscle
  • The thick and thin filaments, along with their associated myofibril proteins, are responsible for muscle contraction.
  • How does muscle contraction work?
    • Influx of calcium ions in the cell
      • as a result of nerve impulses
    • troponin complex pulls tropomyosin molecules away from the G-actin subunits
    • Exposure of the myosin binding sites.
    • The heads of the myosin molecules can bind to the actin subunits, forming cross bridges.
      • active site in each myosin head disrupts the high-energy bond of ATP molecules
      • release of energy moves the myosin head towards the F- actin,
      • when contact is made with the actin subunits, the F-actin is pulled along, causing the myofilament to contract.
  • The coordinated contraction of all the myofilaments of all the muscle cells of a muscle, causes the entire muscle to contract.
relaxation of skeletal muscle
Relaxation of Skeletal Muscle
    • Calcium ions are carried away from the myofilaments
    • Myosin- actin linkages loosen
    • The troponin complex and tropomyosin bind to the myosin binding sites on the F-actin subunits,
  • Myosin and F- actin myofilaments return to their original positions
references
References:
  • Pasternak, Jack J. Human Molecular Genetics: Mechanisms of Inherited Diseases. Hoboken, New Jersey: John Wilkey & Sons Inc., 2005.
  • http://www.lau-verlag.de/anatom/muscleb.jpg. March, 20, 2006
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