pain physiology - modulation and perception Flashcards
what is pain modulation
modification of nociceptive signals by the CNS
what is pain perception
the interpretation of sensation
(cognitive interplay between cognitive and emotional factors)
what information does the spinothalamic tract convey
nociceptive info that is localised and fast pain
and temperature
where does the spinothalamic tract (second order neuron) project to
thalamus (ventroposterolateral VPL nucleus)
where do the third order neurons of the spinothalamic tract project to
primary and secondary somatosensory cortex
where does the second order neuron of the spinoreticular tract project to
reticular formation
where does the third order neuron of the spinoreticular tract project to
limbic structures and the hypothalamus
in terms of pain, what is the limbic system responsible for
subjective interpretation of pain and the emotional response
in terms of pain what is the hypothalamus responsible for
autonomic and visceral responses to pain (stress hormone release, BP and HR changes)
where does the spinomesencephalic tract terminate
various midbrain nuclei (inc. PAG)
PAG is important for
activation of descending analgesic pathways
apart from in the PAG where else does the spinomesencephalic tract terminate
pons (parabrachial nucleus) which then projects to the amygdla (limbic system)
when processing pain, what does the thalamus do
relay and sorting station
when processing pain, what does the primary somatosensory system do
involved in sensory discrimination of pain signals (determines the site, quality, intensity etc)
when processing pain, what does the secondary somatosensory system do
places context around the pain (have you felt this before? it will pass?)
when processing pain, what is the role of the prefrontal cortex
cognitive modulation - how they think about pain
(placebo treatment comes in here)
when processing pain, what is the role of motor and supplementary motor cortices
producing behaviours that come due to pain (proactive, protective, dismissive in relation to sensation)
when processing pain, what is the role of the amygdla/ hippocampus (limbic system structures)
how they feel and memory processing (knowing if they have felt this pain before and if it will be okay)
when processing pain what is the role of the basal ganglia
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)
when processing pain what is the role of the brainstem (PAG)
key players in pain modulation pathways (particularly the spinomesencephalic)
what is the gate control theory
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
which afferent fibres open the pain gate
small diameter fibres Adelta and C
which afferent fibres close the pain gate
large diamater fibres Abeta
besides large diamater a beta fibres closing the pain gate, what else can close the gate
descending pathways, Particulary from PAG
what is the process of a delta and c fibres opening the pain gate
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
what is the process of A-beta fibres closing the pain gate
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
where does non noxious stimuli travelling along a-beta fibres go
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
pain processed at the dorsal horn can also be modulated by higher centres including
brainstem (PAG)
hypothalamus
cerebral cortex and limbic system
the endocannabinoid system is mainly involved in
maintaining homeostasis
what are the two well understood endocannabinoids
anademide and 2AG
where are our endogenous cannabinoids produced
in postsynaptic terminals
after endocannabinoids are produces, what do they do
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
how does the supression of calcium work in the reduction of pain
supressing calcium channels decreased the release of excitatory neurotransmitters which decreases the ability of the action potential to cross the synapse, reducing pain
