pain W5 Flashcards
what communicates external noxious stimuli to the brain?
spinothalamic tract
what type of neurons sense pain and where are they found
specialised nociceptive neurons. sit in epidermis
what contributes to chronic pain?
inappropriate sensitisation
what effect does sensitisation have on pain perception
sensitisation increases the magnitude of the response to pain, when the degree of noxious (harmful) stimulus stays the same
where do pain signals arrive in the brain? what inputs come together here?
pain signal arrives in thalamus. emotional, cognitive and sensory inputs come together and modulate the perception of pain.
why are some people more prone to chronic pain than others?
variations in central pain modulation
descending inhibition of pain?
periaqueductal grey matter - serotonin released here travels downwards and triggers endogenous opioid release in dorsal horn spinal cord interneurons.
endogenous opioids reduce incoming pain pathway activity via opioid receptors on inhibitory neurons
release of inhibition allows onward dopamine signalling, calming pain stimulus and emotional response to pain.
treatment of neuropathic pain? - first line
tricyclic antidepressants - amitriptyline
SNRIs - duloxetine
gabapentin or pregabalin
where do tricyclic antidepressants and SNRIs act?
synaptic cleft
mechanism of gabapentin and pregabalin?
act on calcium channels pre-synaptically to reduce release of pro-nociceptive neurotransmitters. they decrease excitability, especially in the spinal cord.
treatment of neuropathic pain? - second line
capsaicin patch
lidocaine patch
tramadol
how do second line patches (lidocaine and capsaicin) work?
act upon nociceptors in epidermis. lower firing of action potentials from skin to brain.
how do opioids work?
manipulate dopamine signalling in thalamus, brainstem and spinal cord.
what is tramadol?
an opioid!!!!
treatment of neuropathic pain? - third line
botulinum toxin
strong opioids
