Pain part 2 Flashcards
mechano receptors are ___ afferent fibers
- meissner, pacinian
- merkel’s, ruffini
A beta
free nerve ending mechanoreceptors are
A delta and C fibers
warm receptors are ___ type
C
cold receptors are ____ type
A delta
mechanical and thermal nociceptors are ____ type
A delta
polymodal nociceptors are ___ type
C
are A beta myelnated
yes
are A delta myelinated
little
are C type myelinated
no
nociceptor impulses are transmitted by
A delta and C fibres
A delta activation results in
glutamate release at synapse with 2nd order neuron in dorsal horn
C fibre activation results in
glutamate and sub P release
fast pain has ___ receptive fields
small
slow pain has ____ nociceptors and ___ receptive fields
polymodal
large
3 types of pain
nociceptive
inflammatory
pathological
hyperalgesia
exaggerated response to stimuli
allodynia
sensation of pain to innocuous stimuli
peripheral sensitization process
bradykinin or prostaglandin released = sensitize nociceptors = release substance P and CGRP
sub P = histamine release from mast cells
CGRP = dilates blood vessels = release more bradykinin
ventrolateral spinothalamic pathway
primary - dorsal horn - decussates - ascends contralaterally in anterolateral column - thalamus - primary somatosensory cortex
pain in viscera is felt as pain on surface of the body
referred pain
referred pain is based on what theory
convergence projection theory
neuropathic pain
caused by damage/ dysfunction of nerves (central or peripheral)
burning sensation that happens on its own or by a light touch
can result in hyperpathia
central sensitization is due to
projection neuron sensitization- more responsive to inputs
sensitization of the projection neuron results in
disinhibtion = insignificant inputs form other afferents such as A beta mechanoreceptors can now activate the projection neuron
- secondary hyperalgesia
- allodynia
main excitatory NT in CNS
glu
glu receptors are
ionotropic
3 types of glu receptors
AMPA
kainate
NMDA`
LTP is a key trigger for
central sensitization
- opening of NMDARs
substance P and CGRP result in
LTP like results
- phosphorylation of AMPARs and NMDARs = central sensitization
increased depolarization of postsynaptic neuron
activate pathways that lead to release of Ca2+ from smooth ER
site of release of subP and CGRP results in
diffucion away from activated synapse = facilitates neighboring synapses
phosphorylation as a LTP like mech results in
increased sensitivity of AMPARs and NMDARs- NMDARs opened longer
AMPARs can now let Ca2+ in
increased number of AMPARs inserted
calcium effects for LTP like mech
activates enzyme NO synthase = paracrine = increase Glu release
activates COX2 = PGE2 = paracrine = increased Glu
transcription effects of LTP like mech
- increased synthesis of AMPARs
2. increased synthesis of NK1, COX2, other proalgesic protein
NK1 is the
receptor for sub P
disinhibition as a central sensitization mech
PGE2 affects gly receptor = decreased gly inhibition onto projection neuron
primary hyperalgesia
within normal receptive fields
secondary hyperalgesia
central- normally insignificant inputs from outside nociceptors are now able to activate the sensitized projection neuron
allodynia
peripheral = decreased threshold of nociceptor receptors = can be activated by non noxious stimuli central = normally insignificant inputs from A beta afferents are now able to activate the sensitized projection neuron
