Pain patho Flashcards
(30 cards)
Chronic pain
-lasts > 3 months
-nocicpetive (somatic)*
-neuropathic (central or peripheral)
-visceral* (internal organ)
-mixed
*inflammatory
Nociceptive pain
-somatic
-arise from stimuli
-inflammatory
-sharp, localized
-osteosarcoma
-skin/deep tissue
Referred pain
-pain not in same place as injury
inflammatory pain
-throbbing, pulsating
Neuropathic pain
-stabbing, shooting, burning
Visceral pain
-squeezing
Pain is an:
-emotion
-impacts mood
Pain transmission in periphery
-activation of peripheral nervous system (peripheral nociceptors to nerve)
-transmission up DORSAL ROOT GANGLION to DORSAL HORN (spinal cord)
-activate CNS at spinal cord
-input ascends up spinothalmic tract
-transmisson of pain signal to brain by nociception-inhibiting neurons
-descending modulation
-back down spinal cord to periphery
Receptors involved in pain signaling
-temp sensitive (TRP)
-acid sensitive (ASIC)
-chemical sensitive (histamine, bradykinin)
Temp sensitive peripheral receptors
-Transient receptor potential cation channel (TRP)
-TRPV (vanniloid) = heat
-TRPM (melastatin) = cold
Acid sensitive peripheral receptors
-Acid Sensing ion channel (ASIC)
-activated by H+
-conduct Na+
Chemical irritant sensitive peripheral receptors
-histamine
-bradykinin
Reflex upon painful stimuli
-from skin up the AFFerent nerve to spinal cord (A for arrive)
-up EFFerent nerve from spinal cord to muscle (E for exit)
Nerve transmission and ion channels from periphery to spinal cord
-TRP, ASIC, histamine, bradykinin on periphery side
-action potential (sodium channels) in middle
-glutamatergic towards spinal cord end
Pain fibers
-AB-finbers
-Aδ-fibers
-C-fibers
-all Afferent
AB-fibers
-non-noxious
-touch, pressure
-innervate the skin
-fastest
-myelinated
Aδ-fibers
-pain, cold
-myelinated
-fast
-“first pain”, reflex arc (sharp, prickly)
-myelinated
C-fibers
-pain, temp, touch, pressure, itch
-unmyelinated
-slow
-“second pain” (dull, aching)
Peripheral sensitization
-repeated stimuli reduces firing threshold
-substance P
-inc expression of pain receptors during sensitization
Substance P
-vasodilation
-degranulation of mast cells
-release histamine
-inflammation and prostaglandins
Neuropathic pain sensitzation
-peripheral nerve degeneration induces spontaneous activity and spinal sensitization
-inc AMPA and NMDA expression and sensitivity
-neucleotides CGRP
-substance P
-spontaneous afferent activity possibly enhanced expression of Na channel subtypes contributing to enhances cellular excitability and generation of ectopic action potentials (=shooting, burning pain)
Spontaneous Afferent activity in neuropathic pain sensitization
-from peripheral nerve damage
-possible enhanced Na channel expression
=cell excitability
=ectopic action potentials
=shooting, burning pain
Spinal sensitization in neuropathic pain
-from peripheral nerve degeneration
-neuropeptides: CGRP and substance P
-lots of GPCRs on neuron
=activate PLC and PKC
=inc AMPA and NMDA (glutamate) expression and sensitivity
=inc release of glutamate
=hyperexcitability
Pain circutry in brain
-high expression of opioid receptors in brain stem along descending pathway
-opioids block pain signaling from brain to periphery
