Muscles - Anatomy & Physiology

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Introduction

• Skeletal muscle includes muscles of:
  • Posture
  • Movement
  • Respiration

• Two basic types of skeletal myofibre:
  • Type I
    • Grossly red
    • High myoglobin level
    • Slow rate of contraction
    • High oxidative activity
    • Function - postural
  • Type II
    • Grossly white
    • Low myoglobin level
    • Fast rate of contraction
    • High glycolytic activity
    • Function - exercise

• Each muscle is composed of multiple fascicles
  • Each fascicle is composed of multiple polygonal myofibres

Rigor Mortis

• Muscles remain biochemically active after the death of an animal
• Following a period of relaxation, contraction and stiffening occurs
• Due to deficiency of ATP releasing myosin heads from their binding sites at end of power stroke
• Onset faster in ATP deprived animals (starvation, hunting, tetanus...)
• May be absent in cachetic animals
• Disappears due to autolysis or putrefaction
• See general pathology

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