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physiology > peripheral mechanisms of pain > Flashcards

peripheral mechanisms of pain Flashcards

1
Q

what does the sensation of pain sense

A

Localization and intensity

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2
Q

what is the affective component of pain

A

Emotional response (psychological component)

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3
Q

what is acute pain

A

Short term pain witha n identifiable source

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4
Q

what is chronic pain

A

Long term pain with a frequently non-identified source

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5
Q

what nerves do Normal Pain

A

A-delta

C-fibers

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6
Q

what is pathological pain(hyperallgesia)

A

Peripheral and cental sensitization

- increased perception of pain

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7
Q

A-delta fibers make up what percent of cutaneous nociceptors

A

13%

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8
Q

size of A-delta fibers

A

Small and lightly myelinated

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9
Q

conduction veolcity of A-delta fibers

A

12-36m/s

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10
Q

Contenet of A-delta fibers

A

Limited neuropeptide contents

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11
Q

what type of channels are found on A -delta fibers

A

Na+ channels that are mainly TTX-sensitive

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12
Q

what are A-delta fibers nociceptive specific to

A

noxious mechaical stimuli

limited response to noxious heat, chemcial stimuli

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13
Q

what type of pain does A-delta fibers experience

A

1st pain
fast
sharp
well-localized

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14
Q

C fibers make up what percent of cutaneous nocicpetors

A

87%

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15
Q

size of C fibers

A

tiny .2-1.5 micrometers

unmyelinated

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16
Q

conduction velocity of C fibers

A

.5-1.2m/s

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17
Q

what is found within C fibers

A

many contain neuropeptides

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18
Q

channels of C fibers

A

Na+ channels both TTX-Sensitive (typical) and TTX-Resistance

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19
Q

Nocicetpive response of C fibers

A 
Nociceptive specific to mechanical, chemical, thermal
many polymodal (but not all noxious)
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20
Q

what type of Pain do C fibers sense

A

slow, dull, or burning, poorly localized pain

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21
Q

what kind of mechanoreceptors are fuond on A-delta fibers

A

High threshold mechanoreceptors: ENaCS (epithelial sodium channels) to play a role in mechanical nocicption

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22
Q

what receptors are found on Polymodal C-fibers

A

TRP receptors

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23
Q

what do TRP receptors respond for within pain

A

Polymodal characteristics that respond to thermal, chem, and mechanical stimuli

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24
Q

what does the Vanilloid receptor (TRPV1) respond to

A

capsaicin
heat (42 degrees Celsius)
protens

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25
Q

Stimulation of Vanilloid receptors (TRPV1) leads to

A

results in the influx of cations (Na and Ca)

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26
Q

how do Polymodal TRP receptors respond to different types of food

A

chemesthesis (extremes give Pain) middle give burning, tingling, astringency, pungency

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27
Q

what is chemesthesis

A

response of C-fibers (a few A delta) to chemical stimuli

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28
Q

is chemesthesis the same as taste/olfaction

A

NO

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29
Q

what did chemesthesis develop as

A

Part of a chemical defensive mechanism

- initiates expulsive reflexes such as coughing or sneezing

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30
Q

what kind of sensation is chemesthesis

A

produce both painful and non-painful sensations (burning, tingling (carbonation), astringency, pungency

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31
Q

nasal brnach of the trigeminal with chemesthesi

A

Ethmoid (ophthalmic)

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32
Q

oral branch of the trigeminal with chemesthesis

A

Posterior palatine
Nasopalatine (maxillary)
Lingual (Mandibular)

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33
Q

do polymodal nociceptors in the trigeminal system give the same response to different stimuli

A

No

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34
Q

what is the chemesthetic sensation of the ethmoid

A

sensitive to smell salts (ammonia)

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35
Q

what does Nociceptive specific mean

A

responds to 1 stimuli

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36
Q

how can olfaction and chemesthesia be activated

A

ORtho or restronaally

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37
Q

how is olfaction done

A

Olfactory receptors

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38
Q

what does Nasal chemesthesis

A

TRP receptors on ethmoid fibers

taste receptors on specialized olfactory epithelium cells

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39
Q

what are the taste receptsr on specialized olfactory epthelium cells

A

Single Chemosensory cells

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40
Q

where are single chemosensory cells found in the nose

A

scattered throughout nasal epithelium

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41
Q

what innervates single chemosensory cells

A

innervated by Vth nerve

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42
Q

what activates single chemosensory cells

A

Nasal

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43
Q

what does activation of single chemosensory cells lead to

A

initiates respiratory reflexes (apnea)

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44
Q

what is the transduction mechanism for single chemosensory cells

A

Via taste receptor mechansms

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45
Q

what receptors also are found on Vth fibers for chemesthesis

A

TRP receptors

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46
Q

relation between ethmoid nerve response and human perception

A

directly related

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47
Q

what primarily mediates Chemesthesi

A

TRP (some taste receptors in nasal peithelium)

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48
Q

threshold for chemesthesis

A

High threshold

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49
Q

sensations for chemesthesis

A

adversive sensations

50
Q

what reflexes are activatd by chemesthsis

A

Removal reflexes (salivation, coughing, tearing, sneezing, apnea)

51
Q

dental compounds and chemesthsis

A

can activated chemesthesis

52
Q

possitive use of chemesthesis

A

Treatment for certain types of pain (postherpetic neuralgia, arthris)

53
Q

how can capsaicin be used as a drug

A

exhibit desensitization since primary afferent nociceptors can become less reponsive following intense of repeated stimulation

54
Q

how does capsaicin desnsitize primary affferent nocicptor mechanisms

A

Inactivation of voltage-gated ion channels

depletion of neuropeptides

55
Q

where is eugenol found in nature

A

Cloves

56
Q

uses of eugenol

A

Antiseptic, anti-inflammatory, analgesic effects

57
Q

where is eugenol used in dental products

A

Zinc oxide eugenol: cement in pulp, capping, root canal filling
mouthwash and toothpaste

58
Q

potential contraindications to using eugenol

A

allergic

harmful effect on dentin (cytotxic on pulp fibroblasts preventing collagen growth)

59
Q

what receptors does Eugenol activate to produce its analgesic effects

A 
TRP receptors (TRPV3)
Inhibits voltage-gated Na and Ca channel in other class of C-fiber polymodal nocicpetors
60
Q

what fibers are in dentinal tubules

A

A delta fibers extend .1- .2 mm into tubules

61
Q

what does A delta fibers contain in dentinal tubules

A

calcitonin gene related peptide (CGRP) mechanical and thermal sensitivity

62
Q

what does the A-dekta fibers in the Dentinal tubules sense

A

Mechanical and thermal sensitivity

exposed dentin from abrasion and lesions leads to sharp pain

63
Q

what fibers are found in the pulp chamber

A

C-fibers

64
Q

what is found in the C-fibers of the pulp chamber

A

Substance P

65
Q

what does The C fibers in the pulp chamber sense

A

Thermal sensitivity
chemosensitivity to imflammatory mediators
imflammation leads to a dull throbbing pain

66
Q

does Dentinal A-delta fibers respond the same to mechanical forces

A

different response to different mechanical forces

67
Q

can Dentinal A-fibers respond to temp

A

yes, and even responds to temp not in the pain range, but will still give a sharp pain

68
Q

thermal sensitivity of C-fibers (latency, conduction speed, response to cold)

A

Long latency
Slow conduction
response to cold in the pain range

69
Q

Pulpal c-fibers responding to inflammatory mediatory Bradykinin leads to waht latency

A

long latency

70
Q

what does C-fibers respond to and produce

A

Respond to inflammatory mediators and thermal stimuli

produces dull/throbbing pain

71
Q

what does A-delta fibers in dentinal tubules respond to and produce

A

mechanical, thermal, chemical stimuli applid to cavity

-sharp pain

72
Q

the three theories of sharp pain

A

Neuron theory
Hydrodynamic theory
Odontoblast theory

73
Q

how does the neuron theory for thermal pain work

A

Thermosensitivie TRP receptors found on A-delta fibers

Could respond to thermal changes via dentinal fluid

74
Q

how does the hydrodynamic activation of nerve fibers work

A

Possible low threshold mechanoreceptors are found on A-delta fibers
Could act as a transducer for thermal osmotic mechanical effectors on dentinal fluid

75
Q

Afferent Mechanoreceptors for Hydrodynamic activation of nerve fibers

A 
TRPV1 (osmoreceptor)
TRPV2
TRPA1
Piezo2
ENaC
76
Q

how could the odnotoblast act as a sensory cell

A

Odontoblast has process in dentinal tubules

Fluid flow by osmotic, thermal and mechanical stimuli could impact odonotoblast

77
Q

Odontoblast thermoreceptors

A 
TRPV1 (greater than 43)
TRPV2 (greater than 52)
TRPV3 (33-39)
TRPM8 (less than 25)
TRPA1 (less than 17)
78
Q

what odonotblast TRP receptor may have possible mechanoreceptor activation

A

TRPV4

79
Q

Hypothetical steps in Odontoblast signalling to act as a receptor cel

A

Depolarization by various TRP receptors
Initiation of AP
RElease of ATP (possibly non vesicular) via membrane channels
Afferent nerve response via P2X3 receptors

80
Q

what channels are found on Odontoblasts

A

Voltage gated Na+ channels

81
Q

where are TRP receptors found for sharp dentinal pain

A

Both odontoblast and fibers innervating dentinal tubules

82
Q

what explains temperature-induced sharp pain in dentition

A

Temperature sensitive TRP channels on nerve endings and odontobasts

83
Q

what exaplins mechanotransduction of pain by dentinal fluid movement (hydrodynamic theory

A

Piezo2 receptors on nerve endings

84
Q

What can odontoblast signal

A

thermal and possibly mechanical stimulation but synapse to afferent nerve not proven

85
Q

what is hyperalgesia

A

Greater responsiveness to stimuli
spontaneous pain
prolonged pain

86
Q

allodynia

A

response to non-painful stimuli produce pain

87
Q

what happens when there is thermal or mechanical injury

A

C-fiber response and release neuropeptides substance P and CGRP
substance P stimulates mast cells
mast cells release hiatmine
stimulate C fiber
CGRP leads to vasodilation and swelling
this gives mechanical stimulus to C-fiber

88
Q

what happens when there is damages that causes bleeding

A

same factors as thermal and mechanical stimulation

Clot formation
bradykini
stimulates C fiber

Platet products from blood 5-HT (serotonin)
stimulates C fiber

89
Q

Damages leading to infection and immune response can cause what senastion

A

sensitization (increased sensitiive of a neuron to a given stimulus

90
Q

how does infection and immune response lead to sensitization

A

Prostaglandins sensitive C fiber rather than cause direct excitation
cytokines (interleukins, tumer necrosis factor) also sensitive C fibers
Protons released in inflamed tissue stimulate vanilloid (TRPV1) receptors and produce sensitization

91
Q

how does prostaglandins affect a neuron

A

does not directly depolarize the neuron but instead leads it to more likely respond to a sensation

92
Q

how does prostaglandins work

A

Block SK channel

NA+ channels can have a lowered threshold

93
Q

how did we discover how porstaglandins work

A

used TEtrodotoxin ( a puffer fish venom that block some Na channels)

94
Q

effect of Inflammation on the Vanilloid Receptor

A

inflammation leads to lower threshold (22 degrees instead of 42)

95
Q

Mechanism of sensitization of Vanilloid receptor

A

Presence of inflammatory mediators (bradykinin and protons) lower threshold
increased intracellular CA++
CA++ activated phosphorylation of TRPV1 increases sensitivity

96
Q

how does CA++ enter during the sensitization of the Vanilloid Receptor

A

CA++ through receptor

GPCR can increase intracellular Ca++

97
Q

how can peripheral sensitization occur

A

NEurogenic Inflmmation via release of algesics
Direct stimulation of nocicpetors
Sensitization of nociceptors

98
Q

how can neurogenic Inflammation occure in peripheral sensitzation

A 
Subatnce P (from nocicptor itself) stimulates hiatmine relase
CGRP produces swelling (mech stimulus)
99
Q

what objects are invovled in direct stimulation of nociceptors

A

Histamine (mast cells)
Bradykinin (Blood clotting)
5_HT (Blood platelets)

100
Q

what chemicals can lead to sensitization of nociceptors for peripheral sensization

A

Prostaglandins (Effect on K+ (SK) channels)

proton relase in inflamed tissue (TRPV1)

101
Q

How can neurons resppond to non-painful stimuli to produce pain

A

sensitization of TRPV1 lowered temp threshold

Sensitization by prostaglandins lowered mechanical threshold

102
Q

how can neurons response to painful stimuli greater

A

Action of inflammatory mediators augments peripheral stimulus

103
Q

how can pain become spontaneous and prolonged

A

action of inflammatory mediators act as peripheral stimulus

104
Q

Causalgia

A

Burning pain

105
Q

allodynia

A

Light touch leading to pain

106
Q

Sympathetic nerve dystrophy

A

Mild temperature induced pain

107
Q

Phantom sensation

A

sensation in denervated tissue

108
Q

nerve damage can lead to what types of pain

A

Causalgia
Allodynia
Sympathetic nerve dystrophy
Phantom sensations

109
Q

what causes neuromas

A

regenerative capacity of nerves leading to an unorganized mass of nerve tissue due to sprouting and collateral sprouting of injured and uninured fibers

110
Q

effect of neuromas

A

sometimes but not always painful

111
Q

can schwann cells devide

A

Yes

112
Q

what do schwann cells do to help with regenerating axons

A 
PRoduce laminin for substrate for regenerating axons
secrete NGF (nerve growth factor)
113
Q

where is NGF transported

A

to ganglion cell body

114
Q

roll of NGF

A

regulates gene expression and promotes sprouting

115
Q

what genes does NGF regulates

A

Microtubules and microfilaments
neurotransmitter production
ion channels
receptors

116
Q

Ectopic dischage from a C-fiber response

A

Spontaneous activity

Prolonged responses to known stimulus

117
Q

Ectopic dischage from a C-fiber initation

A

Initiation of resposne from atypical site (ganglion)

118
Q

Ectopic dischage from a C-fiber result

A

results from injury-induced increase in Na+ channels

119
Q

Ephaptic transmission

A

A beta fiber acts on the C fiber

120
Q

Ephaptic transmission is a mechanism for what

A

for allodynia

and referred pain

121
Q

how is ectopic dischage evoked

A

Locally, not by normal receptor ending (more Na channels and response to catecholamines)

physiology (32 decks)

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