MSK - PAIN PHYSIOLOGY Flashcards
what is pain?
an unpleasant sensory and emotional experience assoc with actual tissue damage or described in terms of damage
processes involved in pain
transduction
transmission
modulation
perception
transduction
translation of noxious stimulus into electrical activity at the peripheral nociceptor
transmission
propagation of pain signal as nerve impulses through the nervous system
modulation
modification/hindering of pain transmission in the NS eg by inhibitory neurotransmitters like endogenous steroids
perception
conscious experience of pain
causes physiological and behavioural responses
what begins pain?
activation of nociceptors
what are nociceptors?
specific primary afferent neurones normally activated by intense noxious stimuli eg thermal, mechanical or chemical
how do nociceptors relay information to second order neurones?
chemical synaptic transmission
what are the neurotransmitters?
glutamate and peptides eg substance P and neurokinin A
how do second order neurones ascend the spinal cord?
the anterolateral system terminating in the thalamus
which tracts are involved?
spinothalamic tract
spinoreticular tract
what happens in the spinothalamic tract?
pain perception - location and intensity
what happens in the spinoreticular tract?
autonomic responses to pain, arousal, emotional responses, fear of pain
where does the sensory information go after the thalamus?
it is relayed by third order neurones to the primary sensory cortex
what are the types of nociceptors?
Adelta fibres
C fibres
both types of nociceptors are myelinated. true/false
false
only adelta fibres are (thinly myelinated)
what do adelta fibres mediate?
first or fast pain eg lancinating, stabbing, pricking sensations
what do c fibres mediate?
second or slow pain eg burning, throbbing, aching sensations
what are the classifications of mechanisms of pain?
nociceptive
inflammatory
pathological
what is nociceptive pain and when is it provoked?
normal response to injury of tissues by damaging stimuli
only provoked by intense stimulation
what is special about nociceptive and inflammatory pain?
adaptive
n- healing -> pain goes away)
I - promotes repair until healing occurs
what causes inflammatory pain?
activation of the immune system by tissue injury or infection
what activates the pain in inflammatory?
mediators released at the site of inflammation by leucocytes, vascular endothelium and tissue resident mast cells
what is hyperalgesia (caused by inflammatory pain)?
heightened pain sensitivity to noxious stimuli
what is allodynia (caused by inflammatory pain)?
pain sensitivity to innocuous stimuli
when is pain pathological?
when simple analgesics are no longer effective
what is pathological pain treated with?
antidepressants and anti epileptics
what are the two types of pathological pain?
dysfunctional and neuropathic
what is dysfunctional pain?
when there is no identifiable damage or inflammation
what is neuropathic pain?
caused by damage to neural tissue
how is neuropathic pain usually perceived?
burning, shooting, numbness, pins and needles
less localised
what are the 3 time courses of pain?
acute
chronic
breakthrough (all of a sudden on top of chronic pain eg cancer)
how to describe the severity of pain?
mild
moderate
severe
what are the 2 sources of origin of pain?
somatic
visceral
what is referred pain?
deep or visceral pain developed in one part of the body felt in another structure away from its place of development
what causes referred pain?
convergence of nociceptive visceral and skin afferents upon the same spinothalamic neurones at the same spinal level
