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19 Cards in this Set
- Front
- Back
What is Pain?
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multidimensional sensory experience that is intrinsically unpleasant and associated with hurting and soreness
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Define hyperalgesia
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An increased response to a normally painful stimuli.
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Define allodynia?
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A painful response to a normally benign stimulus.
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What is chronic(neuropathic ) pain?
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Pain that persists after the temporal course of natural healing due to central sensitization.
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2 challenges to pain management:
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1) Identify the mechanisms responsible for producing hypersensitivity to pain.
2)Find means of normalizing sensitivity or preventing hypersensitivity from becoming established |
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2 mechanisms involved in hypersensitivity:
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1)Peripheral
2)Central |
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Activated neutrolphils at a site of tissue injury contain activated COX-2 enzyme which is responsible for the production and secretion of what?
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Prostaglandin E2 which reduces the threshold of activation and increases the responsiveness of nociceptor terminals, by binding to the prostaglandin E receptor. (this is peripheral sensitization)
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What is the basic process of peripheral sensitization?
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Inflammatory chemicals/mediators cause changes in key nociceptive receptors and ion channels that determine neuron excitability
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What are two processes implicated in peripheral sensitivity?
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1)Post-translational
-typically phosphorylation of receptors/channels thus lowering threshold of opening or duration of opening; local effect 2)Altered gene expression -signals cause transcription or translation to be altered |
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What is the basic process of central sensitization?
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Increased excitability of CNS neurons, so that normal inputs produce abnormal responses.
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What 2 things occur after the acute phase of central sensitization?
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1)Increased phosphorylation of channels/receptors
2) Increased insertion of channels/receptors into the membrane |
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During central sensitization what changes occur to the glutamate activated NMDA receptor?
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-phosphorylated: which helps it distribute from intracellular to the synaptic membrane and increases its responsiveness to glutamate
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What causes the NMDA receptor to be more responsive to glutamate?
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removal of voltage dependent Mg2+ ion block, so that channel stays open longer
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What is ketamine?
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NMDA receptor antagonist. So it decreases excitability of postsynaptic terminal. Used as a short acting anasthetic, but has many side effects centrally.
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What happens during the persistent phase of central sensitization?
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1) Gene regulation.
-Local:Increased transcription and translation of receptor genes -Globally genes are upregulated for example by COX-2 expression in CNS neurons post injury which causes production of prostaglandin E2 2) Disinhibition -reduced inhibitory transmitter, loss of inhibitory interneuron, altered descending modulation from brain |
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What is the gate theory?
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The transmission of pain from the peripheral nerve through the spinal cord can be altered by: other afferent neurons or controls emanating from the brain.
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What does stimulation of the periaqueductal gray matter do to the sensation of pain?
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It can produce analgesia by causing stimulation of inhibitory neurons that suppress the transmission of pain in the laminae of the spinal cord.
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What is the theory behind using TENS for pain relief?
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Transcutanaeous electrical stimulation is thought to activate A-beta fibers which reduces the flow of pain info to brain
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What happens in the persistent phase of central sensitization during structural reorganization?
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C fibers atrophy, creating vacant synaptic sites in dorsal horn, interneurons also die. A-beta touch fibers inappropriately grow into these zones so that peripheral normal touch stimulates pain.
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