spinal cord

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spinal cord
2012-02-07 02:08:02

lecture 2
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  1. Sensory Cord
    majory relay station
  2. the spinal cord extends from...
    formen magnum to second lumbar vertebra
  3. regions of spinal cord
    cervical, thoracic, lumbar, sacral, coccygeal
  4. How many spinal nerves does the spinal cord give rise to/
    31 mixed nerves
  5. cervical enlargement
    supplies upper limbs
  6. lumbar enlargement
    supplies lower limbs
  7. what runs thru the vertebral canal?
    spinal cord
  8. connective tissue membranes of the spinal cord are...
    dura mater, arachnoid mater, pia mater
  9. dura mater
    outermost layer, continuous with epineurium of spinal nerves
  10. arachnoid mater
    thin and wispy
  11. pia mater
    • bound tightly to surface
    • -forms filum terminale (anchors spinal cord to coccyx)
    • -forms denticulate ligaments that attach the spinal cord to dura
  12. what are the spaces in the spinal cord?
    epidural space, subdural space, subarachnoid space
  13. epidural
    • external to dura
    • -anesthestics injected here
    • -fat-fill
  14. subdural space
    serous fluid
  15. subarachnoid:
    • between pia and arachnoid
    • -filled with CSF
  16. Gray matter
    neuron cell bodies, dendrites, axons,... divided into horns
  17. white matter
    • myelinated axons
    • -divided into 3 columns and into sensory or motor tracts
  18. somatic sensory (SS)
    axons of somatic sensory neurons
  19. visceral sensory VS
    neurons of nisceral sensory neur.
  20. Visceral motor VM
    cell bodies of visceral motor neurons
  21. Somatic motor SM
    cell bodies of somatic motor neurons
  22. white matter in spinal cord is divided into 3 columns/funiculi and have 3 differ types of fibers
    • funiculi: posterior, lateral, anterior
    • -fibers: ascending, descending, trans.
  23. fiibers of the white matter runs in 3 directions
    • ascending fibers - compose of sensory tracts
    • descneding fibers - compose motor tracts
    • commissural (transverse) fibrs: connect opposite sides of cord
  24. generalizations about white matter fiber tract
    • pathways decussate
    • -consist of chain of 2 or 3 neurons
    • exhibit somatotopy (precise spatial relationships)
    • pathways all paired (one on ea. side of spinal cord)
  25. descending pathways divides into two groups
    • -pyramidal (corticospinal) tract
    • -indirect pathways, essentially all others
  26. motor pathwyas involve two neurons
    UMN & LMN (anterior horn motor neuron/final common pathway)
  27. pyramidal tracts originate
    precentral gyrus of brain
  28. pyramidal neuron is what kind of neuron?
    upper motor neuron
  29. UMG synapses where?
    • in anterior horn with LMN
    • -some decussate in pyramids - lateral corticospinal tracts
    • -others at other levels of sc - anterior corticospinal tracts
  30. LMN
    • (anterior horn motor neurons)
    • -exits spinal cord via anterior root
    • -activates skeletal muscles
  31. Pyramidal tracts regualtes ...
    fast and fine (skilled) movements
  32. corticospinal tracts... pathways...
    • location of UMN cell body in cerebral cortex
    • -decussate of UMN axon in pyramids or at level of exit of LMN
    • -synapse of UMN and LMN occurs in anterior horn of sc
    • -LMN axon exits via anterior root
  33. extrapyramidal motor tracts includes
    all motor pathways not part of pyramidal system
  34. extrapyramidal motor tracts; UMN originates
    • in nuclei deep in cerebrum (not in cerebral cortex)
    • -doesnt pass thru pyramids
  35. LMN in extrapyramidal motor tracts...
    is an anterior hor motor neuron
  36. extrapyramidal motor tracts, this system includes..
    rubrospinal, vestibulospinal, reticulospinal, tectospinal tracts
  37. extrapyramidal motor tracts regulates...
    • axial muscles that maintain balance and posture
    • -muscles controling coarse movements of proximal portions of limbs
    • -head, neck, and eye movement
  38. pathway of extrapyramidal tract
    • -UMN cell body location
    • -UMN axon decussates in pons
    • -synapse between UMN and LMN occurs in anterior horn of sc
    • -LMN exits via ventral root
    • -LMN axon stimulates skeletal muscle
  39. reticulospinal tracts originates at...
    reticular formation of brain; maintain balance
  40. rubrospinal tracts originates
    in 'red nucleus' or midbrain; control flexor muscles
  41. tectospinal tracts originate
    in superior colliculi and mediate head and eye movements towards visual targets (flashlight)
  42. ascending pathways
    • central processes of 1st order neurons branch diffusely as enter spinal cord and medulla
    • -some braches take part in spinal cord reflexes
    • -others synapses with 2nd order neurons in cord and medullary nuclei
  43. 3 ascending pathways
    • nonspecific and specific ascending pathways send impulses to sensory cortex
    • responsbile for discriminative touch and conscious proprioception
    • -spinocerebellar tracts send impulses to cerebellumm do nto contribute to sensory preception
  44. nonspecific ascending pathway includes which tracts?
    lateral and anterior spinothalamic tracts
  45. nonspecific ascending pathway; the lateral spinotha. tract transmits
    impulses concerned with pain and temp; to opposite side of brain
  46. nonspecific ascending pathway; the anterior spinotha. tract transmits...
    impulses concerned with crude touch and pressure to opposite side of brain
  47. nonspecific ascending pathway; 1st neuron:
    sensory neuron
  48. nonspecific ascending pathway; 2nd neurons:
    interneurons of dorsal horn; synapse with 3rd order neuron in thalamus
  49. nonspecific ascending pathway; 3rd neuron:
    carry impulse from thalamus to postcentral gyrus
  50. dorsal column tract
    • aka Medial lemniscal pathway
    • -fibers run only dorsal column
    • -transmit impulses from receptors in skin and joints
    • -detect discriminative touch and proprioception
    • 1st order neuron: sensory neuron; synapses with 2nd order neuron in nucleus gracilis and nucleus cuneatus of medulla
    • 2nd ord. neur.: interneuron decussate and ascend to thalamus where it synapses with 3rd ord neur.
    • 3rd ord.(thalamicneurons): transmits impulses to somatosensory cortex (postcentral gyrus)
  51. Spinocerebellar tract
    • transmit info about trunk and lower limb mucles and tendons to cerebellum
    • -no conscous sensation
  52. damage to ventral root
    • flaccid paralysis (limp and unresponsive)
    • -skeletal mucles cant move iether voluntarily/involuntarily
  53. Only UMN of primary motor cortex damaged
    • spastic paralysis (muscles affected by persistent spasms and exaggerated tendon reflexes)
    • -muscles remain healthy longer but movements no longer subject voluntary control
    • -muscles norm. become permanently shortened
  54. transection at any levels results in ...
    • total motor and sensory loss in body regions inferior to site of damage
    • -in cervical region, all four limbs affected (quadriplegia)
    • -between T1 and L1, only lower limbs affected (paraplegia)
  55. spinal shock
    • transient period of functional loss that follows injury
    • -results in immediate depression of all reflex activity caudal to lesion
    • -bowel and bladder reflexes stop, bp falls, and all muscles below injury are paralyzed and insensitive
    • -neural function usually returns within few hours following injury
    • -if not returned within 48hrs, paralysis is permanent
  56. Amyotrophic Lateral sclerosis (Lou gehrig's disease)
    • progressive destruction of anterior horn motor neurons and fibers of hte pyramidal tracts
    • -lose ability to speak, swallow, breathe
    • -death within 5 yrs
    • -cause unknown (90%); others have high glutamate levels
  57. Poliomyelitis
    • virus destorys anterior horn motor neurons
    • -victims die from paralysis of respiratory muscles
    • -enters body in feces-contaiminated water
  58. primary sensory function of dorsal column
    • brings ifno from sensory receptors in periphery all way to primary somatic sensory cortex
    • -via SC, brainstem, and thalamus
    • -3 neuron circuit - sites of synaptic contact
  59. DRG cells
    • from dorsal column; bipolar neurons receive info from peripheral sensory receptors and bring to SC and BS, where info 1st processed
    • -synapse at relay nucleus in medulla
    • [axons] of these neurons from DC nucleus decussate at medulla and cont as medial lemnicus --> thalamus
    • -thalamic neurons send axons to internal capsule, then synapse at primary somatic sensory cortex
  60. corticospinal tract serves...
    • primary motor function; brings info from primary motor cortex to skeletal muscle in periphery (activates muscle contraction)
    • -only ONE synapse
  61. corticospinal tract
    • 1° motor cortical
    • neuron (pre-central gyrus of the frontal lobe)
    • à internal capsule à ventral surface of midbrain à pyramids on ventral surface of medulla.

    • These axons decussate
    • at caudal medulla and travel in the lateral column of the SC à synapse at motor neurons in the ventral horn à these axons travel to the spinal nerve (through ventral
    • nerve roots) à to synapse at the
    • muscles.
  62. intermediatte zone of gray matter
    integration of sensory and motor functions (inter-neurons, reflexes), which serve direct spinal reflexes
  63. white matter: nerve tracts are...
    dorsal column contains...
    lateral column contains...
    • myelin
    • -contains dorsal column
    • -contains...motor descending axons