MUSCLESPART 2

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MUSCLES-PART 2

• Chapter 9

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Neuromuscular Junction and Nerve Stimulus

• Motor Neuron
• Neuromuscular Junction
• Synaptic Cleft
• Synaptic Vesicles
• Molecules-acetylcholine, calcium,
  acetylcholinesterase, sodium, potassium
• States-resting, polarized, depolarized, action
  potential

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Motor Neuron
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Generation of Action Potential

• The outside of the cell is positively charged as
  the inside is negative. (polarized-resting
  potential)
• Abundance of Na on the outside/K on the inside.
  Each wants to move across to create equilibrium.
• Few channels available for facilitated diffusion.
• Electrical signals cause specific Na pumps to
  open. Sodium flows in changing the interior
  charge.(depolarization)
• The inside of the cell becomes positive/outside
  negative.

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Action Potential, contd

• Repolarization occurs when Na channels close and
  K channels open. The resting membrane potential
  is restored.
• This electrical energy wave travels down the
  neuron to the synaptic cleft where electrical
  energy is turned into chemical energy.
• Acetylcholene travels to the muscle cell
  receptors. Chemical energy is transformed back
  into electrical.
• Electrical current travels down the T-tubules to
  stimulate the release of Ca by the terminal
  cisternae.

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Muscle Problems

• Rigor Mortis-Calcium is sequestered in the muscle
  and cant get out, because of the loss of ATP in
  death. Initial 3-4 hours. After 12 hours the
  cells begin to break down.
• Myasthemia Gravis- The receptors are destroyed.
• Curare-Poisons that bind to receptors and block
  nerve messages.
• Organophosphates, Insect, snake venoms-block
  acetylcholinesterase ability to break down the
  protein, so muscles stay in constant tetanus.

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Myograms

• Muscle Twitch
• Wave or Temporal Summation
• Tetanic Contraction
• Threshold Stimulus
• Maximal Stimulus
• Treppe

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Isotonic vs. Isometric

• Isotonic-Tension remains constant, but the length
  changes
• Isometric-Muscle tension increases, but the
  length remains the same.

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Muscle Metabolism

• ATP and Creatine
• Aerobic Respiration
• Anaerobic-Glycolysis and Lactic Acid Formation
• Muscle Fatigue and oxygen debt
• Heat Production

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Force, Velocity, and Duration of Contractions

• Strength determined by
• Velocity and Duration
• Number of muscles involved

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Muscle Fibers

• Red- Slow twitch
• White- Fast Twitch
• Intermediate Fast Twitch

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To Exercise or Not to Exercise??

• Aerobic or Endurance
• Resistance
• Cross Training
• Atrophy
• Overuse