Physiology of pain Flashcards

1
Q

Nociceptive

A

Normal functioning of nocioceptors

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2
Q

Inflammatory

A

Pain in response to inflammation

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3
Q

Neuropathic

A

Pain in response to injury in the nervous system

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4
Q

Nociceptors

A

Primary sensory neurones that detect pain

Have free nerve endings in periphery

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5
Q

Aδ fibres

A

Sharp pricking pain

Well localised
Activation of reflex arcs

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6
Q

C fibres

A

Slow dull ache

Burning pain

Poorly localised

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7
Q

Activation of nocioceptors

A

Pressure

Heat

Cold

Chemical

Tissue damage/ inflammation

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8
Q

Polymodal nocioceptors

A

Most C-fibre nocioceptors are polymodal

Respond to pressure, temperature and chemical

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9
Q

Transduction mechanisms: pressure

A

Mechanically sensitive ion channels

Not yet identified in eukaryotic cells

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10
Q

Transduction mechanisms: temperature

A

Transient receptor potential family of channels

Detect different temperatures

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11
Q

Spinothalamic tract first order neurones

A

Enter dorsal horn

Form tract of Lissauer

Synapse in substantia gelatinosa

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12
Q

Spintothalamic tract second order neurones

A

Cross in dorsal horn at each level

Ascend in anterolateral column to thalamus

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13
Q

Referred pain

A

Convergence of visceral and cutaneous nocioceptors on same second order neurones in spinal cord

Brain perceives pain as cutaneous

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14
Q

Spinothalamic tract third order neurones

A

Ascend to primary somatosensory cortex

Projections to insula and cingulate cortex

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15
Q

Descending regulation ofpain

A

Pain experience determined by many factors

Higher cortical regions can activate descending modulatory pathways

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16
Q

Important regions in descending regulation of pain

A

Periaqueductal gray matter

Rostral ventromedial medulla

17
Q

Inhibition of pain

A

PAG neurones excite RVM neurones which inhibit the spinothalamic tract

18
Q

Endogenous opioid system

A

Opioids play important role in descending inhibition of pain

Especially stress induced analgesia

Opioids are inhibitors

19
Q

Opioids released from

A

Midbrain (periaqueductal gray matter)

Medulla (rostral ventromedial medulla)

Dorsal horn

20
Q

Chemicals released as part of tissue damage

A

ATP

H+

Serotonin/ 5-HT (from platelets)

Histamine (from mast cells)

Bradykinin

Prostaglandin

Nerve growth factor

21
Q

Direct activation of nocioceptors

A

ATP: binds to purinergic receptors

H+: binds to acid-sensing ion channels

Serotonin: binds to 5-HT3 receptors

22
Q

Neurogenic inflammation

A

Activation of one branch of nocioceptor axon, triggers release of substance P and CGRP from anther

Causes

  • vasodilation
  • increased permeability
  • activation of mast cells
  • release of histamine
  • more inflammation
23
Q

Allodynia

A

Non-noxious stimuli produce a painful response

24
Q

Hyperalgesia

A

Noxious stimuli produce an exaggerated pain response

25
Q

Peripheral sensitisation

A

Increase in responsiveness of the peripheral ends of nocioceptors

Driven by tissue injury or inflammation

Bradykinin and NGF reduce threshold of heat activated channels

Prostaglandin reduces threshold of sodium channels

26
Q

Bradykinin

A

Binds to receptor (metatropic- G protein coupled)

Activation of protein kinase phosphorylates TRPV1