Structure of Skeletal Muscle Fiber - Guyton Notes

 

Structure of Skeletal Muscle Diagram.


Muscle Fiber

  • Muscle fibers range from 10 to 80 micrometers.
  • Most fibers run the full length of muscle.
  • About 98% are innervated by one nerve ending.
  • Nerve endings are usually near the fiber middle.

Sarcolemma:

  • The sarcolemma encloses each skeletal muscle fiber.
  • It consists of a plasma membrane and polysaccharide coat.
  • The outer coat contains collagen fibrils.
  • Sarcolemma fuses with tendon fibers at each end.
  • Tendon fibers form bundles that attach to bone.

Filaments and Myofibrils:

  • Each fiber contains hundreds to thousands of myofibrils.
  • Each myofibril has about 1,500 thick myosin filaments.
  • Each myofibril has about 3,000 thin actin filaments.
  • Actin and myosin proteins drive muscle contraction.

Sarcomere and Z discs:

  • Actin filament ends attach to the Z disc.
  • Z discs connect adjacent myofibrils across the fiber.
  • Filament alignment gives skeletal muscle its striated appearance.
  • A sarcomere lies between two successive Z discs.
  • The contracted sarcomere length is about 2 micrometers.
  • Full filament overlap generates maximum contraction force.

Disclaimer: This content is for educational purposes only and not a substitute for professional medical advice.

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