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MD1 Neuroscience > Pain > Flashcards

Flashcards in Pain Deck (83):
1

What is pain?

Unpleasant sensory and emotional experience associated with actual/potential tissue damage

2

What are some physiological stimuli for nociceptive pain?

Mechanical
Termal
Chemical injury

3

What are some clinically relevant stimuli for nociceptive pain?

Abnormal mechanical forces
- Osteoarthritis
Organ injury
- Angina
- Ischaemic claudication

4

What is pain proportional to?

Strength of stimulus

5

Describe the nociceptive pathway in general

Nociceptor encodes info
Relayed to spinal cord/brainstem
Travels via ascending pathways
Much of info goes through thalamus
Up to areas of cortex
Converted into pain perception

6

Is nociception different to somatosensation?

No, it's a subclass

7

What is the threshold for nociceptors?

High threshold

8

What do nociceptors transduce and encode, in general?

Noxious stimuli; eg:
- Strong mechanical forces damaging tissue
- Extremes in temperature
- Chemical stimuli that damage skin like acid

9

What is a noxious stimulus encoded into by the nociceptor terminal?

Electrical signal

10

What is a noxious stimulus?

Stimulus that's damaging/threatens damage to normal tissues

11

What are the three steps in transmission of nociception?

1) Action potential transfers electrical signal from periphery to spinal cord
2) Spinal cord nociceptive neurons integrate and transfer info to brains/other parts of spinal cord - 2nd neuron
3) Thalamic/brainstem nociceptive neurons integrate and transfer information to cortical and other brain regions

12

What are the two components of pain perception?

Sensory
Emotional

13

What does the sensory part of pain perception do?

Identifies discriminative aspects
- Location
- Intensity
- Quality

14

What two ganglia contain primary afferent sensory neuron cell bodies?

Trigeminal ganglia
Dorsal root ganglia

15

What nociceptors do the trigeminal ganglia contain?

Those projecting to head
- Migraine
- Tooth and jaw pain

16

What nociceptors do the dorsal root ganglia contain?

Those projecting to body - most
- Somatic
- Visceral

17

How many axons does a nociceptive fibre have?

1 axon with 2 parts
- Peripheral axon projecting via peripheral nerves to endings in somatic/visceral targets
- Central axon projecting to dorsal horn of spinal cord

18

What are the types of nociceptive fibres?

C fibre
A delta fibre

19

Describe C fibres

Thin
Unmyelinated
Slow

20

Describe A delta fibres

Thin
Myelinated
Medium-fast

21

Compared to touch receptors, are nociceptive receptors fast or slow?

Slow

22

Describe the terminal of the peripheral axon of a nociceptive fibre

Free nerve endings
Not encapsulated in specialised cell like touch receptors

23

In which layers of the spinal cord do the central axons of nociceptors terminate?

Superficial layers - usually laminae 1 and 3

24

What is the nociceptive pathway in the spinal cord?

Those in dorsal horn project to brain via spinothalamic tract on opposite side of spinal cord

25

Where is the point of decussation in the nociceptive pathway?

Dorsal horn - via synapse

26

What white matter tract do nociceptors travel up in the spinal cord?

Anterolateral tract

27

Does all nociceptive information go up to the brain?

No, some only goes to spinal cord > forms reflex circuit

28

What happens when a noxious mechanical stimulus is detected by a nociceptor in the knee region?

Elicits complex withdrawal reflex in both legs without any input from brain

29

What happens to nociceptive information when the spinal cord is anaesthetised?

Perception of pain blocked because ascending pathway blocked
Spinal cord reflexes aren't blocked

30

What type of pain do A delta fibres elicit?

Sharp

31

What type of pain do C fibres elicit?

Slow, burning

32

What type of behaviours are A delta fibres more likely to elicit?

Withdrawal reflex

33

What type of behaviours are C fibres more likely to elicit?

Behaviours that remove stimulus

34

Why can you feel a first and second pain?

When both A delta and C fibres are activated, they transmit signals at different speeds, so pain from A delta fibres is felt first, and quickly. Pain from C fibres follows and remains for a longer time

35

What is inflammatory pain?

Pain felt during active inflammation

36

How is inflammatory pain detected?

Properties of nociceptors altered by chemicals released by damaged tissues/immune system in context of disease

37

What is spontaneous pain?

Pain felt when there is no external stimulus/pain with innocuous stimulus

38

Why do we get spontaneous pain?

Sensory amplification

39

Where can amplification happen?

Peripherally
Centrally

40

What are clinically relevant stimuli for peripheral amplification?

Tissue trauma
Surgery
Joint inflammation; eg: rheumatoid arthritis

41

What is one type transducer protein that's found on nociceptors?

TRPV1

42

What is TRPV1 activated by?

Capsaicin
Heat
Acid
Certain lipids - endogenous equivalents of cannabinoids

43

Where is TRPV1 found?

Most membrane terminals of nociceptors?

44

What type of receptor is TRPV1?

Gated ion channel for Na and Ca

45

Do all nociceptors express the same transducer proteins?

No, different functional classes express different types

46

What type of nociceptors is TRPV1 found on?

Polymodal nociceptors
Heat specialised nociceptors

47

Do all members of the TRP respond to the same stimuli?

No, different members respond to different stimuli

48

Where is TRPA1 found, and to what does it respond?

In airways
Responds to
- Nicotine
- Formalin
- Others

49

What does TRPM8 respond to?

Menthol

50

How does the "inflammatory soup" affect nociceptor activity?

Chemical signals released by tissue damage/disease
Detected by different receptors on nociceptor terminals
Downstream cell signalling causes sensitisation

51

How does downstream signalling affect nociceptor sensitisation?

Changes properties of terminal and lowers threshold

52

Define hyperalgesia

Increased response to normally painful stimulus

53

Define allodynia

Painful response to normally innocuous stimulus

54

How can allodynia be clinically detected?

Stroke skin softly with paintbrush/cue tip > intensely painful to patient

55

What can central sensitisation result from?

Increased nociceptor activity after peripheral sensitisation

56

Describe secondary hyperalgesia

If you have localised painful stimulus, get localised pain induced by stimulus
Over time, hyperalgesia extends into areas that aren't damaged because initial signal activates regions of spinal cord, including across segments
Amplifies info coming in from adjacent nociceptive and non-nociceptive afferent fibres

57

What is neuropathic pain?

Nervous system lesion or disease/ marked neuroimmune response causing pain

58

What are examples of a CNS problem causing neuropathic pain?

Stroke
Spinal cord injury
MS

59

What causes central amplification in neuropathic pain?

Neuroimmune interactions in periphery and CNS

60

What causes peripheral amplification in neuropathic pain?

Nerve trauma
Toxic and metabolic neuropathies
Herpes zoster
AIDS

61

What does it mean for neuropathic pain to be maladaptive and persistent?

Abnormal amplification maintained independent of lesion/disease

62

How can peripheral neuropatic pain occur?

Damage to peripheral nerves > develop inappropriate branches
Pain perception altered

63

How can a cut terminal continue to produce spontaneous electrical activity?

Cell damage > nerve loses input > central part of axon continues to generate electrical activity

64

What are complex regional pain syndromes (CRPS)?

Multifactorial pain disorder
- Pain and other clinical abnormalities
- Sensory
- Motor
- Autonomic
- Signs and symptoms spread distally glove- or stocking-like in affected limbs
- Sudden change for pain after fracture/surgery to persistent burning pain

65

What is the cause of CRPS?

No identifiable pathology

66

What are examples of functional pain syndromes?

CRPS
Migraines
Myalgia

67

Define acute pain

Lasts for short time
Occurs after surgery/trauma/other condition
Warning to body to seek help

68

Define sub-acute pain

Progressing to chronic pain
Can be prevented
Transition phase

69

Define recurrent pain

Occurs on cyclical basis
- Migraine
- Pelvic pain

70

Define chronic pain

Lasts beyond time expected for healing

71

What area in the brain does pain activate?

No single area
Activates network

72

What roles do the periaqueductal grey and rostral ventral medulla in the brainstem play in pain?

Form chain projecting back down to spinal cord
Modulate pain

73

What are some major classes of centrally acting analgesic drugs?

Opioids
NSAIDs
Anticonvulsants
Tricyclic antidepressants (TCAs)
Serotonin-noradrenaline reuptake inhibitors (SNRIs)
Alpha 2-adrenergic agonists
Cannabinoids

74

What is an example of an opioid?

Morphine

75

What are two examples of anticonvulsants?

Gabapentin
Pregabalin

76

What is an example of an alpha 2-adrenergic agonist?

Clonidine

77

What is an example of a cannabinoid?

Marijuana

78

How can pain experience be modulated?

Feedback pathway to spinal cord that can inhibit/amplify info brought by nociceptors

79

What effect does fear have on the perception of pain?

Hypoalgesia

80

What cortical areas are involved in the modulation of pain?

Anterior cingulate
Prefrontal
Insula

81

By giving a person a placebo and telling them that it reduces pain, what effect does this have in the brain?

Produces genuine analgesia via endogenous pain modulation
Placebo analgesia reduced/prevented by opioid antagonists

82

What effect on the brain does it have by giving a patient a nocebo?

Hyperalgesia

83

What are the factors in the psychobiological model of pain perception?

A delta and C nociceptive input
Injury
- Peripheral and central sensitisation
Chemical and structure
- Neurodegeneration
- Metabolic
- Maladaptie plasticity
Cognitive set
- Hypervigilance
- Attention
- Distraction
- Catastrophising
Mood
- Depression
- Catastrophising
- Anxiety
Context
- Pain beliefs
- Expectation
- Placebo

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