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physiology > Central mechanisms of Pain > Flashcards

Central mechanisms of Pain Flashcards

1
Q

what is the Localization and intensity of pain

A

the Sensation of pain

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2
Q

what is the Emotional response (Psychological component) of pain

A

Affective component

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3
Q

what is short term pain with an identifiable source

A

Acute

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4
Q

what is long term pain with a frequently non-identified source

A

Chronic pain

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5
Q

what meidates Normal pain

A

A-delta and C-fibers

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6
Q

what mediates Pathological pain (hyperalgesia

A

Pheripheral and central sensitization

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7
Q

where is oral and facial pain processing done

A

Caudalis (part of the spinal trigeminal nucleus)

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8
Q

what is the sensory portion of the spinal cord

A

Medullary dorsal horn

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9
Q

pain vs non-pain senations of the medullary Dorsal Horn

A

Pain is more on the outer surface (supperficial)
non-pain is found deeper
But there is some overlap

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10
Q

what do Nociceptive specific neurons respond to

A

to only painful stimuli

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11
Q

what do Wide Dyanmic range neurons respond to

A

Both painful and non-painful stimuli

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12
Q

Does the PNS have something like wide dynamic range neurons

A

NO

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13
Q

Cell types found in the medullary dorsal horn

A

Nociceptive specific neurons

Wide Dynamic range neurons

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14
Q

REceptive fields of the Wide Dynamic Range Neurons in the medullary dorsal horn

A

HAve large Receptive fields

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15
Q

how is the receptive fields of wide Dynamic range neurons different from that of the PNS

A

PNS can’t be in 2 different branches

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16
Q

where do Nociceptive specific neurons tuerminate in the medullary dorsal horns

A

In superficial layers I and II

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17
Q

where do Non-nocicpetive neurons terminate in the medullary dorsal horn

A

In deeper layers III, IV, and V

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18
Q

where does OVerlap occure in the medullary dorsal horn

A

In layers II and V

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19
Q

Convergence in the medullary dorsal horn

A

High degree of convergence

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20
Q

what Afferents converge in the MDH

A

Nocicpetive and Non-nociceptive afferents

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21
Q

what types of things converge in the MDH

A

Submodality convergence

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22
Q

what emerges in the MDH

A

wide dynamic range neurons emerge

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23
Q

what happerents to peripheral affernets of different receptive fields

A

they converge

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24
Q

what peripheral affernts converge their receptive fields

A 
Cutaneous
Joint
Muscle
Tooth pulp (max and Mandibular)
other nerves (SLN: superior laryngeal nerve)
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25
Q

Roll of MDH and referred pain

A

MDH is the neural substrate for referred pain

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26
Q

spread of pain from the teeth

A

Spread all along the head due to refered pain

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27
Q

how does MDH help to explain referred pain

A

Pain and non-pain afferents converge on “pain-signaling” neurons

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28
Q

why can’t convergence on the MDH explain Referred pain alone

A

Because pain only occures under pathological conditions ( not a normal sensation)

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29
Q

what may cause the MDH to start doing referred pain under pathological conditions

A

something is preventing the activation of convergent input in MDH under “normal” conditions

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30
Q

Does Peripheral sensitization explain referred pain

A

Not entirely: peripheral sensitization mostly increases with C-fiber sensitivity
- does not explain larger areas of Pain (increased receptive fields)

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31
Q

How could peripheral sensitization explain the larger areas of pain due to referred pain

A

following severe nerve injury there could be ephaptic connections between pain and non-pain fibers that could enlarge receptive fields

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32
Q

what fibers are used to Induce central sensitization

A

A-beta fibers

33
Q

evidence for central sensitization

A
  • Injected Capsacian to Activate TRPV1 giving a burning sensation
  • pressure block done near capsaicin, so can’t feel light touch, so no allodynia
  • on hand with no pressure block, could feel light touch so there was allodynia
    • light touch neuron must communicate with pain nueron to give allodynia when pain is already pressent
34
Q

what does the pressure block block in the central sensitization test

A

blocks A-beta and A delta fibers

35
Q

Steps of Central Sensitization

A
  1. C fiber afferent barrage (acute pain, inflammation)
  2. MDH Neuron response
    - Depolarization by substance P (tachykinin)
    - modification of NMDA receptor (removal of Mg++ block)
    - Increase in conductance NMDA receptor
  3. previously ineffective A-fiber now effective
    - A-diber release of glutamate effective at NMDA receptor
    - larger receptive field
    - response to innocuous stimuli by A-beta fibers now induces pain
36
Q

Pain threshold of normal teeth

A

Very high pain threshold

37
Q

Pain threshold in inflamed teeth

A

much lower pain threshold

38
Q

what teeth tend to have lower pain thresholds in the mouth when the tooth is inflammed

A

Lower pain threshold also in healthy contralateral heathy teeth

39
Q

why do teeth contralateral to inflammaed teeth expereince low pain thresholds

A

Inflamed teeth are sensitizing central neurons with input from healthy contralateral side to make them more sensitive

40
Q

is pain confined to the MDH

A

Not confined

41
Q

Effects of trigeminal tractotomy (Cut C1-C3)

A

Anesthesia (no sensation: C1-C3)
Analgeais (no pain on face)
Hypalgesia (diminished mucosal pain)
Pulpal pain still intact

42
Q

why do a trigeminal tractotomy

A

Intractable facial pain from cancer

43
Q

what is done in a trigeminal tractomy

A

Descending Vth tract tract cut at level of obex (C1-C3 cut at all afferents)

44
Q

what happens to stroke patients with lesion in pons

A

Intraoral touch, thermal, and pain all diminished

45
Q

what proves that pain is not confined to MDH

A

TRigeminal tractomy in humans ( intraoral mucosa still shows pain sensations and tooth pulp pain intact)
Lesion in pons (diminishes intraoral and perioral pain)

46
Q

Afferent pain fibers projecting from the MDH go to the:

A

Oral Motor N (Pons and Mdeulla
N. submedius
VPM

47
Q

what is the sensory pain pathway

A

Afferent fibers
MDH
VPM (thalamus)
S1 (Cortex)

48
Q

what is the emotional pain pathway

A

Afferent fibers
MDH
N. Submedius
Cingulate cortex

49
Q

Roll of the oral motor N in the pain pathways

A

reflex function:
Jaw opening
sweating
Increased HR and BP

50
Q

receptive field in the VPM

A

small

51
Q

response time of the VMP

A

Onset/offset of stimulus

52
Q

what si the response to stimulus of the VPM

A

linear

53
Q

receptive field of the submedius

A

LArge

54
Q

response time of the N. submedius

A

outlasts stimulus

55
Q

what does the N. submedius neurally respresent

A

NEgative emotion to outlast stimulus

56
Q

Peripheral changes of phantom pain

A 
Sprouting (neuroma)
Ectopic impulses
Ephaptic transmission
Sympathetic-afferent coupling
Down/upregulation og transmitters
Down/upregulation of channels and transduction molecules
57
Q

Central changes for phantom pain

A 
Sprouting
Central sensitization (unmasking of synpases
58
Q

receptive field and why of VPL and Somatosensory cortex in pain processing in the forebrain

A

Small receptive field nad localization of pain

59
Q

neural response time of VPL and Somatosensory cortex in pain processing in the forebrain

A

Neural response track pain stimulus onset and offset

60
Q

how does the VPL and somatosensory cortex mediate phantom pain

A

Somatosensory reorganization

61
Q

Neural response of the N. submedius and Cingulate cortex

A

Outlasts stimulus (poor localization)

62
Q

what part of pain does the N. submedius and cingulate corteex involve

A

the emotional component of pain

63
Q

effect of anxiety on pain perception

A

Increases pain perception

64
Q

empathy and pain

A

Empathy for another in pain activates some cortical areas

65
Q

placebo and pain

A

Suppresses pain perception

66
Q

How did scientist create a low vs High anxiety condition

A

Low: Visual cues to indicate whether subject would receive a moderate pain
High: visual cue indicated may receive high pain

67
Q

results of low and high anxiety test

A

pain to same stimulus was rated higher in high anxiety state

68
Q

what happens in the brain following induction of anziety

A

Increased activity in anerior cinguate cortex

69
Q

what does Empathy do to the brain

A

Activates the anterior cingulate and insula

70
Q

how did they test for empathy

A

couples get cue for pain
only one person gets pain
both showed pain activity in cinguate cortex

71
Q

Does empathy also activate SI or SII

A

Does not activate SI or SII

72
Q

what does the lack of SI or SII activation for empathy show

A

separates anatomical difference between emotional and somatosensory component of pain

73
Q

what does the placebo effect activate

A

The anterior cingulate cortex like that of opioids

74
Q

what mediates the placebo effect

A

endogenous opoids

75
Q

Roll of Nalxone with testing the placebo

A

bloacks endogenous opioids so the placebo effect does not work

76
Q

what do the multiple CNS sites for modulation of pain contain

A

Endogenous opioids to suppress pain

77
Q

what are the Multiple CNS sites to modulate pain

A

Forebrain: ACC
Midbrain: PAG
Rostral ventraomedial medulla

78
Q

what are the Descending projections from medulla

A

excitatory

inhibitory

79
Q

steps of Presynaptic inhibition

A

Descending projection to local enkephalinergic interneurons
Enkephalins work both pre- and postsynapticall
pre-synaptic suppression of Ca++ channels suppresses neurotransmitter release
Postsynaptic effect of opening K+ channels

physiology (32 decks)

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