Neuro Exam 4.6

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brau2308
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216454
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Neuro Exam 4.6
Updated:
2013-04-28 20:41:39
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neurology neuroscience neuroanatomy
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review of neuro part 6 for exam 4
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  1. What are the specific types of reflexes?
    • flexor reflexes
    • DTR/myotactic/stretch reflex
    • GTO reflex/inverse reflex/tendon reflex
  2. What activates flexor reflexes?
    Type III and IV fibers (acute and chronic fibers)
  3. What type of muscles are involved with flexor reflexes?
    flexor mm
  4. What is the purpose of flexor reflexes?
    protection
  5. Where do all tracts lead?
    to LMNs which allow mm to contract
  6. DTR/myotactic/stretch reflex:
    • contraction of agonistic and synergistic mm following stretching of agonistic mm
    • stretch m -> it (along w/ synergist) contracts
  7. What type of reflex is it when mm stretch caused by hitting quadriceps tendon?
    DTR/myotactic/stretch reflex
  8. What type of fibers are activated during DTR/myotactic/stretch reflex?
    type Ia
  9. Where do activated type Ia fibers in DTR/myotactic/stretch reflex travel to?
    dorsal root to synapse w/ LMN that returns to same mm that was stretched
  10. What are DTR/myotactic/stretch reflexes important for?
    mm tone and upright posture
  11. How many neurons are involved with the DTR/myotactic/stretch reflex pathway?
    2 neuron pathway
  12. What is the receptor organ in the DTR/myotactic/stretch reflex pathway?
    muscle spindle (neuromuscular bundle [3-4mm in length])
  13. What do muscle spindles do?
    measure length and rate of change of length in extrafusal fibers
  14. What type of reflex is the DTR/myotactic/stretch reflex?
    proprioceptive reflex (involves skeletal mm)
  15. What are the modified cells inside the muscle spindle called?
    intrafusal fibers
  16. What are muscle cells outside the capsule called?
    extrafusal fibers
  17. Where do muscle spindles run in comparison to the extrafusal fibers?
    parallel to the extrafusal fibers
  18. What are the types of intrafusal fibers?
    • dynamic nuclear bag (Ia)
    • static nuclear bag (II)
    • nuclear chain fiber (II)
  19. Which type of intrafusal fiber is most important?
    dynamic nuclear bag
  20. Why do we need different types of intrafusal fibers?
    all function to differentiate b/w static and dynamic change in length and rate of change in length of skeletal mm
  21. What is the noncontractile portion of the intrafusal fiber?
    middle of intrafusal fiber that doesn't contral
  22. Annulospiral ending:
    wrapped around noncontractile portion of the intrafusal fibers
  23. What is the annulospiral ending attached to?
    part of Ia fiber (dynamic nuclear bag)
  24. What does the annulospiral ending do?
    register length and change (receptor organ of Ia fiber)
  25. What type of neuron is a Ia fiber?
    proprioceptive
  26. What type of receptors are muscle spindles?
    mechanical stretch receptors
  27. Where is the flower spray ending?
    • located laterally on either side of the annulospiral ending
    • around contractile portion on either side of noncontractile
  28. What are flower spray endings?
    • endings of secondary fibers (type II -- nuclear chain fibers and static nuclear bag) of intrafusal fibers
    • secondary endings
  29. Primary sensory endings for skeletal mm=
    Ia fibers
  30. Describe synapses of Type Ia fibers of DTR/myotactic/stretch reflexes:
    type Ia fibers (dynamic nuclear bag w/ annulospiral ending) become primary fiber and monosynaptically synapse in SC w/ alpha motor neuron which innervate the same extrafusal fibers of the mm or synergistic mm (no interneuron involved)
  31. Describe synapses of Type II fibers of DTR/myotactic/stretch reflexes:
    type II fibers (static nuclear bag or nuclear chain fiber w/ flower spray endings) become secondary fiber and only synapse w/ alpha motor neurons that attach to extrafusal fibers of the same mm
  32. What is the efferent component of a DTR?
    alpha motor neurons
  33. Where are the cell bodies of alpha motor neurons?
    ventral horns
  34. What do alpha motor neurons innervate?
    extrafusal fibers
  35. How can alpha motor neurons get inhibition of antagonistic mm activity?
    using Renshaw cells (reciprocal inhibition)
  36. What are Renshaw cells?
    inhibitory neurons in gray matter of SC and associated with alpha motor neuron; choose to inhibit 1 mm and exite 1
  37. What makes up the bulk of skeletal mm?
    extrafusal fibers
  38. What type of reflex is GTO reflex/inverse reflex/tendon reflex?
    proprioceptive reflex (deals w/ skeletal mm)
  39. Where is the receptor for GTO reflex/inverse reflex/tendon reflex?
    encapsulated receptor at junction b/w muscle and tendon
  40. How are receptors of GTO reflex/inverse reflex/tendon reflex arranged?
    separately arranged in a series, however muscle spindles are parallel
  41. What do GTO/inverse/tendon reflexes cause?
    autogenic inhibition
  42. What type of fibers do GTO/inverse/tendon reflexes use?
    type Ib fibers (afferent)
  43. What do GTO/inverse/tendon reflexes prevent when doing a hard workout?
    prevents tearing of mm when maxing out
  44. What do GTO do?
    measure tension and rate of change of tension in tendon
  45. What does the GTO/inverse/tendon reflex do?
    • adjust m activity in concert w/ info from muscle spindle and descending controls (suprapinal input)
    • prevents tearing of mm by keeping antagonistic m from being excessively stretched or contracted
  46. What happens during the synapse of GTO/inverse/tendon reflex?
    type Ib synapse w/ Renshaw cells (inhibitory interneurons) to inhibit alpha motor neuron activity
  47. What does the GTO/inverse/tendon reflex cause?
    loss of mm tone and sometimes functionally gives way (muscle collapses)
  48. Do GTO/inverse/tendon reflex always work?
    • sometimes doesn't work
    • i.e., Achilles tendon or gastroc tears

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