pain physiology - modulation and perception Flashcards

1
Q

what is pain modulation

A

modification of nociceptive signals by the CNS

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2
Q

what is pain perception

A

the interpretation of sensation
(cognitive interplay between cognitive and emotional factors)

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3
Q

what information does the spinothalamic tract convey

A

nociceptive info that is localised and fast pain
and temperature

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4
Q

where does the spinothalamic tract (second order neuron) project to

A

thalamus (ventroposterolateral VPL nucleus)

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5
Q

where do the third order neurons of the spinothalamic tract project to

A

primary and secondary somatosensory cortex

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6
Q

where does the second order neuron of the spinoreticular tract project to

A

reticular formation

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7
Q

where does the third order neuron of the spinoreticular tract project to

A

limbic structures and the hypothalamus

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8
Q

in terms of pain, what is the limbic system responsible for

A

subjective interpretation of pain and the emotional response

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9
Q

in terms of pain what is the hypothalamus responsible for

A

autonomic and visceral responses to pain (stress hormone release, BP and HR changes)

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10
Q

where does the spinomesencephalic tract terminate

A

various midbrain nuclei (inc. PAG)

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11
Q

PAG is important for

A

activation of descending analgesic pathways

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12
Q

apart from in the PAG where else does the spinomesencephalic tract terminate

A

pons (parabrachial nucleus) which then projects to the amygdla (limbic system)

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13
Q

when processing pain, what does the thalamus do

A

relay and sorting station

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14
Q

when processing pain, what does the primary somatosensory system do

A

involved in sensory discrimination of pain signals (determines the site, quality, intensity etc)

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15
Q

when processing pain, what does the secondary somatosensory system do

A

places context around the pain (have you felt this before? it will pass?)

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16
Q

when processing pain, what is the role of the prefrontal cortex

A

cognitive modulation - how they think about pain
(placebo treatment comes in here)

17
Q

when processing pain, what is the role of motor and supplementary motor cortices

A

producing behaviours that come due to pain (proactive, protective, dismissive in relation to sensation)

18
Q

when processing pain, what is the role of the amygdla/ hippocampus (limbic system structures)

A

how they feel and memory processing (knowing if they have felt this pain before and if it will be okay)

19
Q

when processing pain what is the role of the basal ganglia

A

closely linked with the motor and supplementary motor cortices

behaviors that are produced due to pain (proactive, protective, or dismissive in relation to the sensation)

20
Q

when processing pain what is the role of the brainstem (PAG)

A

key players in pain modulation pathways (particularly the spinomesencephalic)

21
Q

what is the gate control theory

A

that there is a neural gate in the dorsal horn that can inhibit or fascilitate afferent (sensory) impulses depending on the activity and different afferent nerve fibres

22
Q

which afferent fibres open the pain gate

A

small diameter fibres Adelta and C

23
Q

which afferent fibres close the pain gate

A

large diamater fibres Abeta

24
Q

besides large diamater a beta fibres closing the pain gate, what else can close the gate

A

descending pathways, Particulary from PAG

25
Q

what is the process of a delta and c fibres opening the pain gate

A

these fibres travel to the dorsal horn where they release substance p to contact an excitatory interneuron which opens the pain gate and facilitates the afferent signal up the second order neuron

26
Q

what is the process of A-beta fibres closing the pain gate

A

these fibres travel to the dorsal horn where they release substance p to contact an inhibitory interneuron which closes the pain gate, inhibiting the pain signal from travelling any further

27
Q

where does non noxious stimuli travelling along a-beta fibres go

A

some stimuli branches off to travel up the dorsal column (medial lemniscus)

whilst there is also another branch thrown off that inhibits the pain gate. this is why nice non noxious sensation (rubbing/ massage) activates inhibitory interneurons

28
Q

pain processed at the dorsal horn can also be modulated by higher centres including

A

brainstem (PAG)
hypothalamus
cerebral cortex and limbic system

29
Q

the endocannabinoid system is mainly involved in

A

maintaining homeostasis

30
Q

what are the two well understood endocannabinoids

A

anademide and 2AG

31
Q

where are our endogenous cannabinoids produced

A

in postsynaptic terminals

32
Q

after endocannabinoids are produces, what do they do

A

after being produced in the postsynaptic terminals, they travel backwards and bind to CB1 receptors in the first oder neuron and then inhibit neurotransmitter relase through the supression of calcium channels

33
Q

how does the supression of calcium work in the reduction of pain

A

supressing calcium channels decreased the release of excitatory neurotransmitters which decreases the ability of the action potential to cross the synapse, reducing pain