pain Flashcards
stages of pain sensation
- periphery: detection and transmission to spinal cord (1st ON)
- spinal cord: processing, transmission to brain (thalamus) (2nd ON )
- brain: perception, learning, response
- modulation: descending tracts
what is nociceptin
detection of tissue damage by specialised transducers connected to A-delta and C fibres
nociceptors
free nerve endings of A-delta and C fibres
respond to thermal, chemical, mechanical, noxious stimuli
primary afferents/1st order neurons
cell body in dorsal root ganglion
first order neurones
synapse at spinal cord
spinal dorsal horn
first order synapse
spinothalamic tracts
major ascending tract for nociception
arises in rexed lamina 2 and 5
second relay station
thalamus
where does thalamus connect to
cortex
limbic system
brainstem
allondynia
decreased threshold for nociceptor response
hyperalgesia
exaggerated response to normal and supranormal stimuli
spontaneous pain
spontaneous activity in nerve fibres
central sensitisation
response of second order neurons in the CNS to normal input both noxious and non-noxious
3 main components of central sensitisation
wind-up
classical
long-term potentiation
wind up
involves only activated synapses
homosynaptic activity dependant progressive in response of neurons
manifests over the course of stimuli and terminates with stimli
classical
opening up of new synapses (silent nociceptors)
heterosynaptic acitivity dependent plasticity
immediate onset w approp stimuli
outlast initial stimuliu duration
can be maintained even at low levels of ongoing stimuli
long term potentiation
involves mainly activated synapses
occurs primarily for very intense stimuli
acute pain
<1mo usually obvious tissue damage pain resolves upon healing protective function prescence of noxious stimuli usually nociceptive
chronic pain
at least 3mo
pain beyond expected period of healing
usually has no protective function
nociceptive, neuropathic or mixed
what is nociceptive pain
sensory experience that occurs when specific peripheral sensory neurones (nociceptors) respond to noxious stimuli
nociceptive pain features
localised site of injury
time limited, resoles with healing
can be chronic
responds to conventional analgesics
what is neuropathic psin
psin initiated/caused by a primary lesion or dysfunction in the somato-sensory nervous system
neuropathic pain features
may not be localised - pain occurs in neurological territory of affected structure (nerve, root, spinalcord)
almost always chronic
responds poorly to conventional analgesics
nociplastic pain
pain that arises from altered nociception despite no clear evidence of damaged/threatened tissue causing activation of nociceptors
