Pain

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  • Created by: ksjvsba
  • Created on: 17-01-16 19:35
What are the three dimesions of Pain (Melzach and Casey)
Sensory discriminative (temporal and spatial, intensity, location, quality), Motivational affective(emotional, avoidance), cognitive evaluative (meaning and context)
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Specificity theory
descates- fibre cord and bell. pain pathways dedicated to brain regions
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Evidence of specifity, bottom up theory
Late 19th century- specific pain receptors- parcicon corpulus (rought and vibrations), Meissners corpules (light tough and speed), Ruffinis corpules (vib and stretching)
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Pain receptors - Adelta fibresa are...
1-6um axon, fast, thick, thinley mylenated, initial sharp, highly localise, 5-36 velocity
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ABeta fibres are...
low threshold, toughing, thick mylenation, 36-90 velocity, 6-14um axon
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C fibres
High thresh, dull aching pain, seconary, 0.2-1 velocity, 0.2-1um axon, not mylenated
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High order pathways are:
spinoreticular and spinothalamic
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Spinothalamic tract
sensory aspects of pain, dorsal horn just about spinal level-> thalamuc (md)VPL, 3rd order neurons ascend to somator sensory cortex
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Spinoreticular tract
2nd order tract-> reticular in brain stem. Project to intralamina, nuclei of thalamus -> hypothalamus cortex , emotional aspects of pain
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Cognitive Modulation of Pain
Distraction, placebo and perceived control
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Injury without pain..
eposiodic analgsia (no severity), congential analgesia (no pain)
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pain without injury...
phantom limb pain
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Gate Control Pathway
allow accending nociceptors through the brain - explains why rubbing heps
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Periacqueductal Gray (PAG)
recieves nociceptor input from doral horn and afferent information from hypothalamus and amygdala. Rich in opiod receptors and involved in defensive/fear
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Rostral VEntromedial Medulla (RVM)
connected to PAG. minimal input from spinal cord, projects heavily to dorsal horn. involved in sensitizing the periphery to sensory inputthought to contrain both on and off cells
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Behavioural Activation of Descending Modulation
Stress induced analgesia is blocked by naxalone and RVM lesions. Conditioned fear analgesia is blocked by lesions in the amygdala, RVM or naxalone injected into the PAG. Safety signals block opiate analgesia- Lesions of RVM
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PAG associated with modulation of pain
distraction, percieved control and competiting nociceptor input
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Card 2

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Specificity theory

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descates- fibre cord and bell. pain pathways dedicated to brain regions

Card 3

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Evidence of specifity, bottom up theory

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Card 4

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Pain receptors - Adelta fibresa are...

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Card 5

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ABeta fibres are...

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