Muscle Anatomy and Physiology

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Muscle Anatomy and Physiology

• Structure or Anatomy
• Function or Physiology
• Muscle Fiber Types
• Tension Development

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Levels of Fibrillar Organization
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Sarcomere Design

• Each myofibril is composed of a series of
  sarcomeres
• Sarcomeres are composed of protein filaments held
  in relative position by connective tissue called
  Z line
• Myosin filament is long rod-like protein looks
  like a set of golf irons
• Actin filament is globular protein looks like
  strings of pearls

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Muscle Physiology

• Energized myosin head attaches to binding site on
  actin filament
• Once attached, myosin head swivels and pulls the
  actin across which pulls Z line toward middle of
  myosin filament
• Binding of ATP molecule disassociates myosin
  crossbridge from actin
• Splitting of ATP to ADP energizes myosin head for
  another cycle

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Muscle Physiology

• If all of the components necessary for muscle
  contraction are present, why arent cross bridges
  always moving and the muscle always in a state of
  contraction?

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Role of Calcium in Contraction

• At rest, tropomyosin covers the actin binding
  site so the myosin head cannot attach
• When excited, calcium is released from the
  sarcoplasmic reticulum in the muscle cell to bind
  with troponin which is attached to the
  tropomyosin covering the binding site
• Troponin pulls the tropomyosin off the binding
  site so the myosin head can attach

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Muscle Excitation

• This sequence is repeated as long as there is
  calcium present
• Muscle relaxes when calcium pumped back into
  sarcoplasmic reticulum

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Muscle Fiber Types

• Differentiation of Types twitch rates
• Physiological Differences
• Performance Advantages and Disadvantages

• Genetics, Gender, Training, and Muscle Fiber
  Plasticity
• Muscle Fiber Recruitment Order

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Muscle Fiber Types
I
IIa
IIb
Twitch
Slow
Fast
Fast
Color
Red
Red
White
Energy
Oxidative
Ox/
Glyc
Glycolytic
Fatigue
Resists
Resists
Fatigues
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Muscle Fiber Plasticity

• Muscle fiber type appears to be genetically fixed
• Training can alter oxidative capacity of type II
  fibers

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Muscle Fiber Recruitment depends on Intensity not
Speed

• Order of muscle fiber recruitment is from most
  oxidative to least oxidative
• Order of fiber recruitment is from slowest to
  fastest
• Order of fiber recruitment is from smallest
  diameter to largest diameter
• Order is Type I ?Type IIa ? Type IIb

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Tension Development

• Neuromuscular Excitation
• Summation and Tetanus
• Gradation of Muscle Contraction