583 neural physiology

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  1. How many muscle fibers are fired
    Varies considerably among muscles
    innervation ratio
  2. What is released in order to generate movement?
  3. Controlled by the CNS
    Peripheral nervous system
  4. Innervation ratio for delicate movements
    Low ratio (5-10)
  5. Innervation ratio for gross movements
    High ratio (several thousands)
  6. Feed Back Loop:
    Motor and sensory cortex -> _________ _>motor cortex with indication of movement, intensity and length of muscle movement
  7. Activation:
    Action potential (AP)generated when several sub-threshold impulses arrive in succession
    Temporal summation (time component)
  8. Activation: 
    AP generated when several presynaptic terminals on the same motor neuron are stimulated simultaneously
    Spatial summation (from all different directions signal comes)
  9. Which principle?
    In normal muscle, once the neuron is activated and the impulse reaches the NMJ,AcH is released and all the muscle fibers in that motor unit contract simultaneously
    All or None Principle
  10. Where can fatigue occur in the motor unit pathway?
    Anywhere. the brain, brain to spinal cord or from motor neuron to muscle
  11. Serves to smooth out muscle contraction
    Neural inhibition
  12. Protective function; excessive force is not produced
    Minimizes musculoskeletal injury
    Neural inhibition
  13. Can occur for supramaximal performance
    -Verbal encouragement
  14. Classification of Motor Units:
    Technique of classifying fibersby staining the muscle tissue for various enzymes
    Histochemical Analysis
  15. What are the 3 factors considered for classification of motor units?
    • Morphological characteristics 
    • Contractile properties 
    • Metabolic characteristics 
  16. Classification of Motor Units:
    Physical characteristics
  17. Classification of Motor Units:
    Velocity of contraction
  18. Classification of Motor Units:
    Enzyme characteristics
  19. Light: Slow contractile speed
    Light: Low glycolytic capacity
    Dark: High oxidative capacity
    Slow Oxidative, Type I
  20. Dark: Fast contractile speed
    Dark: High glycolytic capacity
    Light: Low oxidative capacity
    Fast Glycolytic, Type II
  21. Contractile Properties of Motor Units:
    Slow twitch
    Low tension
    Fatigue resistant
    Type I
  22. Contractile Properties of Motor Units:
    Fast twitch
    Moderate force
    Fatigue resistant (intermediate)
    Type IIa
  23. Contractile Properties of Motor Units:
    Fast twitch
    High force
    High fatigue
    Type IIb
  24. True or false:
    Slow twitch = low tension = fatigue resistant
  25. True or false:
    High twitch = High tension = High fatigue
  26. Would you want Type I or Type II as a sprint athlete?
    Type II - High glycolytic, low oxidative
  27. Would you want Type I or Type II as an endurance athlete?
    Type I - High oxidative, low glycolytic
  28. Is fiber type genetic?
    Yes - twin studies
  29. Is the fibre type distributed fairly consistent among major muscle groups?
  30. True or false:
    Some muscle groups are predominantly ST or FT.
    • True.
    • ST - soleus & gastroc.
    • FT - ocular (eye)
  31. True or false:
    You cannot modify musle fibers through training
    False. You can modify 20-30% (metabolic and contractile properties)
  32. Fibre Type: Are there significant gender differences?
  33. Fibre type true or false: 
    Variation is quite large, especially in men
  34. If you do endurance training for extended time the fast twitch motor units will increase _____ ______ and become more like slow twitch.
    oxygen capacity
  35. Based on contractile speed, can FT convert to ST?
  36. Why are muscle fibers lost from spinal cord injury?
    • Atrophy
    • Loss of capillaries
  37. After a spinal cord injury do fast twitch become slow twitch?
    • No. Slow twitch (metabolic) become more like fast twitch.
    • Lose oxidative capacity because of loss of capillaries
  38. No visible change in muscle length
    Cross bridges link to generatemuscle tension
    Muscular tension insufficient toovercome resistance
    Energy metabolised from anaerobic sources
    ATP is broken down
    Isometric (Static) Contraction
  39. Constant tension throughoutthe ROM
    -Misnomer – tension variesthroughout ROM
    -Muscle is only as strong as itsweakest point (sticky point)
    Isotonic (Dynamic) Contraction
  40. Constant velocity throughout the ROM
    Muscle stressed throughout the ROM
    Isokinetic (Dynamic) Contraction
  41. Types of Muscle Contractions:
    􀀹 Muscle shortens while overcomingresistance
    􀀹 Muscle tension varies throughout ROM
    􀀹 Length – tension relationship differs among muscle groups
  42. Types of Muscle Contractions:
    Muscle lengthens againstresistance
    Peak muscle tension exceeds thatattained during concentriccontractions
    -Optimal linkage of cross bridges?
  43. 􀀹 Soreness/stiffness in muscles and joints which is onset a few hoursafter exercise and lasts for 2 to 4 days
    􀀹 Usually occurs after unaccustomed physical activity
    Delayed Onset of Muscle Soreness (DOMS)
  44. Not due to the accumulation of lactic acid
    Possible causes include:
    􀂃 Connective tissue damage: hydroxproline in urine
    􀂃 Cellular damage: can detect CK and myoglobin in serum
    􀂃 Metabolite accumulation: osmotic changes cause edema
    􀂃 Muscle spasm: due to transient ischemia
    Delayed Onset of Muscle Soreness (DOMS)
  45. -small alpha motor neuron
    -ST (slow twitch)
    -Low force output
    Endurance Type Activities
  46. -large alpha motor neuron
    -ST/FT (slow twitch then includes fast twitch as velocity of contraction increases and force output continues)
    -High force output
    -with fatigue recruit more slow twitch
    Power Type activity 
  47. recruit motor units in specific patterns (can be learned)
    Voluntary Modulation
  48. True or false:
    Motor units are not plastic and their biochemical properties cannot be altered by the amount of physical activity/inactivity
    False. They are plastic and biochemical properties can be altered by physical activity/inactivity
  49. True or false:
    Motor unit recruitment patterns may be altered in diseased/disabilitystates which can adversely affect the energy cost of physical activity inindividuals with neuromuscular disorders
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583 neural physiology
583 neural physiology
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