The Case of the Screaming Agony Flashcards
3 types of pain
nociceptive, inflammatory, neuropathic
nociceptive pain
normal response to real or threatened non-neuronal tissue damage
is nociceptive pain reversible or irreversible?
reversible
how do nociceptors transmit pain to dorsal horn?
via ad or c fibres
a-delta fibres
fast acting and transmit initial sharp pain, some myelin
c fibres
transmit slower, dull pain, no myelin
Where are nociceptors located? (5)
skin joints connective tissue muscle bone
what does visceral pain feel like?
diffuse, aching, cramping, poorly localised
autonomic symptoms associated with visceral pain
sweating, nausea, vomiting
which fibres transmit visceral pain?
which fibres transmit visceral pain?
autonomic fibres so poorly localised
2 types of nociceptive pain
somatic and visceral
inflammatory pain
pain that signals some type of tissue damage and inflammation
how does peripheral sensitisation happen?
inflammatory mediators e.g. cytokines, substance P sensitive local nociceptors and cause exaggerated responses
what happens at sites of tissue damage?what gets released?
cytokines, prostaglandins, ATP, H+, bradykinin, NO released, all directly or indirectly activate or sensitise nociceptors
neuropathic pain
pain from damage to neurons of either the peripheral or central nervous system
symptoms of neuropathic pain
sharp, stabbing, tingling, burning, electric shock; onset of high intensity (Example: phantom pain)
allodynia
Pain due to a stimulus that does not normally provoke pain
Hyperalgesia
excessive sensitivity to painful stimuli
hyperpathia
pain that continues after stimuli removed
what sensory changes does nerve damage cause?
sensory loss
increased responsiveness to noxious and innocuous stimuli
what pain mechanisms involved in vascular pain?
all 3: neuropathic, nociceptive and inflammatory mechanisms
Define pain
unpleasant sensory and emotional experience associated with actual or potential tissue damage
factors influencing pain
factors influencing pain
physiological, social, psychological, pain tolerance, personality, cultural
which inflammatory mediators directly activate nociceptors?
ATP and H+
what stimuli do a-delta fibres respond to?
mechanical or thermal stimuli
what stimuli do c fibres respond to?
mechanical, thermal or chemical
2 spinal pathways which carry pain
spinothalamic
spinoreticular
path of neurons in spinothalamic pathway
1st order neurone enters dorsal horn, ascends 1/2 levels in tract of lissaeur, synapses with 2nd order neurone which crosses over, ascends to thalamus
2 spinothalamic tracts
lateral neo-spinothalamic tract
medial paleo-spinaothalamic tract
what is the dorsal horn divided into?
Rexed lamina
where do c fibres terminate in dorsal horn?
substantia gelatinosa aka lamina 2
where do a-delta fibres terminate in dorsal horn?
lamina 1 and 5
The destination of the neospinothalamic tract is ___________.
ventral posterior lateral nucleus of thalamus
what does Neo-spinothalamic tract carry?
sensory-discriminative aspect of pain
destination of paleospinothalamic tract is?
medial thalamus, hypothalamus and periaqueductal gray
where does spinoreticular tract end?
reticular formation in the medulla oblangata, pons, and midbrain
Where do 3rd order neurons synapse?
primary somatosensory cortex, also may project to insula and anterior cingulate cortex
Where is the insula and what does it do?
deep within the lateral sulcus, deals with visceral nociceptive input
where is anterior cingulate cortex and what does it do?
around front of corpus callosum, does attention and memory of pain
gate control theory of pain
theory that if a-beta fibres are activated by mechanical stimuli they activate inhibitory interneurons which stop c fibres transmitting pain (if you press an injury it may stop hurting)
where do descending pain inhibitory pathways originate?
periaqueductal gray
reticular formation
nucleus raphe Magnus
what receptors are expressed in PAG, reticular formation and nucleus raphe Magnus?
endogenous opioid receptors
how do descending inhibitory pathways work?
serotonin and noradrenaline action inhibit substance P and glutamate release at level of dorsal horn
what part of pain pathway do NSAIDs work on?
nociceptor terminals
what part of pain pathway do antidepressants work on?
enhance activity of descending inhibition
what parts of pain pathway do opioids work on?
brain, nociceptor terminals and dorsal horn
what neurotransmitter do alpha delta fibres release?
glutamate
what neurotransmitter do c fibres release?
substance P
how does central sensitisation work ?
prolonged glutamate release causes more NMDA receptor insertion or hyper responsiveness
where is the nucleus raphe Magnus located?
in rostroventrolmedial medulla
how does endogenous opioid system reduce pain?
blocks 1st order neurones from releasing NT
stops release of AP from 2nd order neurones
less pain transmission
