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Dent 6600 - Physiology > Peripheral mechanisms of pain > Flashcards

Peripheral mechanisms of pain Flashcards

1
Q

“normal” pain is mediated by

A

A-delta & C fibers

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2
Q

pathological pain “hyperalgesia” is mediated by

A

peripheral and central sensitization

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3
Q

which fiber type makes up majority of cutaneous nociceptors?

A

C fibers (87%)

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4
Q

this nociceptor type is unmyelinated and very small

A

C fibers

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5
Q

this nociceptor type contains a limited neuropeptide content

A

A-delta fibers

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6
Q

nociceptive specific to noxious mechanical stimuli with limited response to thermal and heat

A

A-delta fibers

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7
Q

nociceptive specific to mechanical, chemical, thermal stimuli

A

C-fibers

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8
Q

nociceptor for “first pain” - fast, sharp, well localized

A

A-delta fibers

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9
Q

nociceptor for “second pain” - dull, burning, poorly localized

A

C fibers

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10
Q

this type of pain receptor can be found on odontoblasts and therefore has a possible role in tooth pain

A

TRP receptor

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11
Q

Trigeminal nerve branches with prominent chemesthesis

A

nasal - ethmoid
oral - nasopalatine
posterior palatine
lingual nerve

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12
Q

chemesthesis is mediated by:

A

TRP receptors

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13
Q

tooth pain fibers

A

A-delta & C fibers

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14
Q

dentinal tubules have what kinds of fibers?

A

A-delta fibers

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15
Q

Pulp chamber has what kind of fibers?

A

C fibers

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16
Q

A-delta fibers of dentinal tubules

A

extend a little into dentin tubules
contain CGRP
mechanical & thermal sensitivity
sharp pain

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17
Q

C-fibers of pulp chamber

A

dull, throbbing apin
contain Substance P
thermal sensitivity
chemosensitivity to inflammatory mediators

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18
Q

fiber type responds to algesic stimuli such as Bradykinin (BK)

A

pulp chamber C-fibers

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19
Q

A-delta fibers respond to which types of chemical stimuli?

A

NH4Cl and NaCl

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20
Q

C-fibers respond to which types of chemical stimuli?

A

Bradykinin (BK) and Histamine

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21
Q

Fibers respond mainly to inflammatory mediators

A

Pulpal C-fibers

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22
Q

theories of sharp pain

A
  1. neuron theory
  2. hydrodynamic theory
  3. odontoblast theory
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23
Q

smear layer for pain transduction

A

necessary to avoid pain when high pressure applied to dentinal tubules
used in root canal walls

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24
Q

EDTA does what?

A

dissolve smear layer = pain

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25
Q

odontoblast TRP thermoreceptors

A

TRPV1, 2, 3
TRPM8
TRPA1

26
Q

odontoblast TRP mechanoreceptors

A

TRPV4
TRPM3
TRPP1, 2

27
Q

purinergic signaling

A

part of odontoblast transducer theory

extracellular signaling mediated by purine nucleotides (adenosine, ATP)

28
Q

Steps in odontoblast signaling

A
  1. depolarization by TRP receptors
  2. initiation of AP
  3. release of ATP via membrane channels
  4. afferent nerve response via P2X3 channels
29
Q

P2X3

A

a type of nerve fiber found in pulp

present in both myelinated and unmyelinated pulpal nerve fibers

30
Q

P2X3 receptors

A

nociceptive afferent nerve fiber

31
Q

odontoblasts have what kinds of channels?

A

voltage gated Na+ channels

32
Q

variety of TRP receptors can be found where?

A

odontoblasts

dentinal tubule innervating fibers

33
Q

hyperalgesia

A

greater responsiveness to stimuli, allodynia

pain is prolonged and spontaneous

34
Q

allodynia

A

response to non-painful stimuli produces pain

35
Q

CGRP leads to

A

vasodilation and swelling

mechanical stimulus to C-fiber

36
Q

Substance P leads to

A

mast cell > release histamine > stimulate C fiber

37
Q

events after thermal or mechanical injury:

A

C-fiber releases substance P or CGRP > SP releases mast cells > histamine release > C fiber stimulated > CGRP leads to swelling > mechanical stimulus to C fiber

38
Q

sensitize C-fibers rather than direct excitation

A

prostaglandins
cytokines
protons released from inflamed tissue that stim. vanilloid receptors

39
Q

cytokines that sensitize C-fibers

A

interleukins, TNF

40
Q

role of NGF in peripheral sensitization

A

induces local receptor trafficking
retrograde transport of signaling endosomes to promote gene expression
bind to high affinity TrkA receptor forming complex that sensitizes nociceptor

41
Q

T/F? Prostaglandins directly depolarize neuron

42
Q

TTX

A

fish substance that blocks sodium channels

43
Q

A-fiber sodium channels are TTX _____ and potassium channels are ________

A

TTX sensitive ; Bradykinin

44
Q

C-fiber sodium channels are TTX _______ and potassium channels are __________

A

TTX resistant ; Bradykinin and SK

45
Q

prostaglandins block what channel

46
Q

Vanilloid receptor (TRPV1 or V1) lower threshold by:

A
  • inflammatory mediators (BK and protons)
  • Ca++ activated phosphorylation of VR1 receptor
  • increase in # of receptors
47
Q

neurogenic inflammation

A

substance P > histamine release

CGRP > swelling, vasodilation

48
Q

direct stimulation of nociceptors

A

histamine (mast cells)
bradykinin (blood clotting)
5HT (platelets)

49
Q

sensitization of nociceptors

A

prostaglandins (affect K+ channels)
proton release from inflamed tissue (TRPV1 vanilloid)
NGF (increases receptor trafficking)

50
Q

mechanisms of hyperalgesia - allodynia

A

TRPV1 sensitization = lower temperature threshold

Prostaglandin sensitization= lower mechanical threshold

51
Q

inflammatory mediators do what to peripheral stimulus

A

augment (add to) = greater response to painful stimuli, makes it prolonged and spontaneous

52
Q

causalgia

A

burning pain

53
Q

sympathetic nerve dystrophy

A

temperature induced pain

54
Q

NGF secreted by

A

Schwann cells

55
Q

promotes sprouting and regulates gene expression

56
Q

NGF transported to

A

ganglion cell body

57
Q

Schwann cells produce _______ for regenerating axons

58
Q

ectopic discharge

A
  1. spontaneous activity
  2. prolonged response to known stimulus
  3. initiation of response from atypical site (ganglion)
  4. injury > increase in # Na+ channels
    response to catecholamines
  • activity evoked locally, not by normal receptor ending
59
Q

ephaptic transmission is the mechanism for:

A

allodynia (pain response to nonpainful stimulus)

referred pain

60
Q

sprouting

A

increased fiber density

induced by NGF

61
Q

contain CGRP

A

dentinal tubule fibers

62
Q

contain Substance P

A

pulpal fibers

Dent 6600 - Physiology (3 decks)

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