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VET 404: Neurology > Pain & Nociception > Flashcards

Pain & Nociception Flashcards

1
Q

nociception

A

activity in the nociceptors and nociceptive pathways (central and peripheral)
- initiated by a noxious stimulus
- involves pain processing pathways
- causes physical changes (BP, HR, cortisol)

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2
Q

pain

A

perception of the noxious stimulus; the unpleasant feeling and behavioral response to a noxious stimulus

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3
Q

5 key factors of pain

A
  1. has a physical cause
  2. it is a feeling (sensory and emotional experience)
  3. requires consciousness
  4. it is subjective
  5. it is unpleasant
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4
Q

reason for pain

A

overall protective and critical for survival

alerts the body of the threat and triggers protective behaviors to limit damage and promote healing

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5
Q

allodynia

A

pain experienced in response to a non-noxious stimulus

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6
Q

hyperalgesia

A

exaggerated response to a noxious stimulus

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7
Q

acute pain

A

pain that follows tissue damage (has a specific cause)
- short lived - resolves as tissues heal
- has protective function

nociceptive and physiologic/adaptive

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8
Q

chronic pain

A

pain that persists when the initial cause is gone
- long lasting
- no protective function
- difficult to treat

pathologic/maladaptive pain

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9
Q

somatic pain

A

pain from the skin, muscles, bone, soft tissues, teeth, etc

can be precisely localized/perceived at the affected area due to a LARGE # of fibers that go to SPECIFIC parts of the spinal cord that innervate the area

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10
Q

visceral pain

A

pain from internal organs, glands, smooth muscle

diffuse and poorly localized due to a SMALL # of fibers that spread extensively in the spinal cord that innervate the area

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11
Q

referred pain

A

visceral pain that can be felt at somatic sites due to viscero-somatic convergence

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12
Q

viscero-somatic convergence

A

the overlap of somatic and visceral nerve fibers in the spinal cord that causes altered processing of visceral and somatic pain inputs

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12
Q

viscero-somatic convergence

A

the overlap of somatic and visceral nerve fibers in the spinal cord that causes altered processing of visceral and somatic pain inputs

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12
Q

viscero-somatic convergence

A

the overlap of somatic and visceral nerve fibers in the spinal cord that causes altered processing of visceral and somatic pain inputs

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12
Q

viscero-somatic convergence

A

the overlap of somatic and visceral nerve fibers in the spinal cord that causes altered processing of visceral and somatic pain inputs

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13
Q

neuropathic pain

A

pain caused by a lesion/disease of peripheral nerve fibers

can be acute or chronic

ex. amputation, spinal cord injury, diabetic neuropathy, cancer

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14
Q

neuropathic pain

A

pain caused by a lesion/disease of peripheral nerve fibers

can be acute or chronic; often involves nervous system hyperexcitability

ex. amputation, spinal cord injury, diabetic neuropathy, cancer

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15
Q

nervous system hyperexcitability

A

bombardment of excitatory signals to CNS + a decrease in inhibitory signals that causes hyperexcitability

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16
Q

pain processing pathway

A

transduction –> transmission –> modulation –> perception

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17
Q

transduction

A

conversion of a noxious stimulus into an electrical signal (AP)

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18
Q

where does transduction occur

A

peripheral nociceptors

noxious stimulus triggers depolarization –> activates nociceptors –> generates AP

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19
Q

what is action potential frequency proportional to

A

intensity and duration of the noxious stimulus

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20
Q

nociceptors

A

peripheral endings of nociceptive A-delta and C fibers in their target tissues

have a HIGH activation threshold - requires very intense/prolonged stimuli

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21
Q

what type of signals do nociceptors detect

A

mechanical, temperature, and chemical

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22
Q

unimodal nociceptors

A

only get activated by 1 type of stimulus

usually A-delta fibers

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23
Q

polymodal nociceptors

A

activated by a wide variety of noxious stimuli

usually C fibers

24
Q

silent nociceptors

A

MIAs - mechanical insensitive afferents

nociceptors with an extremely high activation threshold that are usually inactive and require previous sensitization to be activated

25
Q

transmission

A

action potential propagation from periphery to the CNS

26
Q

where does transmission occur

A

along A-delta and C fibers

27
Q

process of transmission

A

AP generated at nociceptors travels along nerve fibers causing voltage gated Na channels to open –> AP propagates down fiber

28
Q

A-delta fibers

A

FAST, medium sized, lightly myelinated nerve fibers involved in IMMEDIATE SHARP pain

29
Q

C fibers

A

SLOW, small, unmyelinated nerve fibers involved in slow burning/dull pain

30
Q

what type of fiber is more abundant in somatic tissues

A

A-delta fibers

causes somatic pain to be more immediate/sharp

31
Q

what type of fiber is more abundant in visceral tissues

A

C fibers

causes visceral pain to be more slow/dull

32
Q

A-beta fibers

A

FASTEST, large, myelinated nerve fibers involved in NON-PAINFUL touch

NOT involved in nociception

33
Q

dorsal horn of the spinal cord

A

site of A-delta/C fibers synapsing with secondary afferents

34
Q

main neurotransmitter released by A-delta/C fibers

A

glutamate

35
Q

main neurotransmitter released by A-delta/C fibers

A

glutamate

36
Q

main receptor on secondary afferent neurons in the spinal cord

A

AMDA receptors

37
Q

AMDA receptors

A

glutamate receptor on the secondary afferent neuron

causes depolarization and further propagation of AP to the CNS

38
Q

secondary pain afferents

A

located in the dorsal horn of the spinal cord

types:
1. interneurons
2. propriospinal neurons
3. projection neurons

39
Q

interneurons

A

major target for primary afferent neurons (A-delta/C)

can be excitatory or inhibitory to pain transmission to CNS

used as a target for pain meds

40
Q

propriospinal neurons

A

transfer inputs between spinal cord segments

41
Q

projection neurons

A

transfer inputs from spinal cord to supraspinal centers in the brain via ascending tracts

42
Q

wide dynamic range neurons (WDRn)

A

special projection neurons (or interneurons) that receive information from all primary afferents (A-delta, C, A-beta) to detect noxious and non-noxious stimuli

receptors cover a large area with high overlap –> many WDRns activate in response to single stimulus

43
Q

modulation

A

up or down regulation of action potential transmission; affects how much of the action potential reaches the brain to determine amount of pain experienced

44
Q

where does modulation occur

A

dorsal horn of the spinal cord

45
Q

function of ascending tracts

A

transmit the action potential from dorsal horn of the spinal cord to supraspinal centers

46
Q

gate control mechanism

A

activation of nerves that do not transmit pain signals (A-beta) to alleviate the final pain feeling

non-painful mechanical stimuli –> activates A-beta (FAST) fibers –> activates inhibitory interneurons at the dorsal horn –> decreases painful signals sent to the brain

47
Q

descending modulation

A

feedback mechanism from supraspinal centers to the dorsal horn of the spinal cord that change pain perception in the brain

supraspinal centers send excitatory/inhibitory interneurons/projection neurons to dorsal horn –> facilitates amount of pain signal that gets sent back up to the brain

48
Q

how does emotional state/manipulation of attention alter pain perception

A

descending modulation

not focusing on pain/positive thoughts –> increased inhibitory signals sent from supraspinal centers –> less pain felt

focusing on pain/negative thoughts –> decreased inhibitory signals sent from supraspinal centers –> more pain felt

49
Q

what are two descending modulary systems

A
  1. PAG-RVM (tonically active - inhibitory)
  2. Pontine-NE Cell Groups (activated by PAG-RVM)
50
Q

sensitization

A

increased responsiveness of the nervous system (PNS or CNS) to noxious stimuli

makes nervous system hyperaware during pain to decrease further damage –> results in allodynia and hyperalgesia

produces reversible changes in nervous system (if long lasting, can become chronic)

51
Q

peripheral sensitization

A

sensitization that occurs at the site of injury

caused by local inflammation that changes the environment of the nociceptors

results: allodynia and primary hyperalgesia (at site of injury)

52
Q

central sensitization

A

sensitization that occurs at the dorsal horn neurons in the spinal cord

caused by sustained noxious stimulation leading to neuronal hyper-responsiveness

results: allodynia and secondary hyperalgesia (spreads to surrounding areas)

53
Q

WIND-UP phenomenon

A

an increase in neuron responsiveness after sustained noxious stimulation leading to an increased number of APs generated following each individual stimulus

increased efficacy of synaptic transmission leads to central sensitization of WDRns (less glutamate required to transmit pain)

54
Q

what receptors and nerve fibers are involved in the WIND-UP phenomenon

A

NMDA receptors
C fibers repetitively firing

55
Q

perception

A

awareness of the feeling of pain leading to negative emotions, behavioral responses, and learning

56
Q

where does perception occur

A

cortical regions of the brain

subcortical regions project to the cortex to modify

57
Q

pain experience

A

multidimensional experience of pain based on the characteristics:
1. sensory-discriminative
2. emotional-motivational
3. cognitive-evaluative

58
Q

sensory discriminative aspect of pain experience

A

somatosensory cortex

involves pain intensity, location, quality and duration

59
Q

emotional motivational aspect of pain experience

A

limbic system

emotional reaction to pain

60
Q

cognitive evaluative aspect of pain experience

A

prefrontal cortex

pain meaning and its possible consequence

VET 404: Neurology (23 decks)

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