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pain
- is a warning signal, protection
- is a perception that arises from te activation of nociceptive receptors
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acute pain
- readily identifiable stimulus
- short duration high intensity
- not real difficult to treat
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chronic pain
- present past the normal time frame required for healing
- long duration low intensity
- difficult to treat
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A-alpha
- motor nerves
- large myelinated axons
- fast transmission
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A-beta
- sensory nerves
- medium to large myelinated axons
- relatively fast transmission
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A-delta
- sharp localized pain
- small lightly myleniated axons
- relatively slow transmission
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C
- generalized diffuse pain
- small unmyelinated axons
- slow transmission
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first order
- cell body in dorsal root ganglion
- axon terminates in dorsal horn
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second order
- cell body in dorsal horn
- axon crosses and terminates in one of several places
- VPL of thalmus (fast)
- reticular formation or midline and intralaminar nuclei of thalmus (slow)
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third order
cell body in VPL, reticluar formation, or midline and intralaminar of thalmus
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2 modulator systems
within CNS to regulate pain perception both exhibit their influences at the spinal cord level segmental and suprasegmental
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segmental
- ascending or gate control
- non-nociceptive afferent (A-beta) input supresses nociceptive transmission between 1 and 2 order pain neurons
- reduction in net discharge of 2 order pain neurons closing the gate
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clinical relevance of segmental pain control
- reduce pain w/o pharmacologic means
- pain must be peripheral in orgin (not CNS)
- treatment goal is to recruit as many A-beta fibers as possible from the region in which the pain is originating
- onset of pain relief is generally rapid but carry over is short
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suprasegmental
- descending or endogenous opiate
- two levels
- hormonal and neuronal
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hormonal
periventricula grey matter of the hypothalmus and pitutary gland provide for hormonal pre and post synaptic inhibition of 2 order pain projection neurons (impact on dorsal horn region)
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neuronal
- involves periaqueductal grey (midbrain region)
- input from the ascending spinoreticular tract
- PAG activate the descending inhibition pathway in the DLF and VLF
- fibers of DLF and VLF provide for pre and post synaptic inhibition of 2 order pain projection neurons
- endogenous serve as neurotransmitters in this system
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clinicla relvance of suprasegmental pain control
- can reduce pain w/o pharmacologic means
- recruit A-delta and C fibers these do not have to be from the same area as the region
- onset of pain os generally delayed but carry over is longer
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assessment of pain
- pain drawing- fillled by physician or pt, reliability/validity are very questionable
- rating scales- reliabilty is reasonable and validity is questionable
- questionaires- mcgill pain, SIP, SP-36, Oswestry (low back pain) reliabilty and validity are reasonably good
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