Sensory physiology of pain Flashcards
what are the two dimensions of pain?
- sensory discrimination - perception of external or internal noxious information and localization of the site 2. motivation affective - emotional and sympathetic responses and associated (learning) behaviors
initial superficial pain is carried by what type of fibers?
Ad
superficial delayed pain is carried by what type of fibers?
C
visceral pain is carried by what type of receptors?
C
what are transient receptor potential families?
group of receptors that allows for influx of sodium and calcium upon activation, thus initiating a receptor potential
what are activators of chemical stimuli?
- potassium 2. low pH 3. substance P 4. bradykinin
what are sensitizers of chemical stimuli?
- prostaglandins 2. leukotrienes 3. ATP 4. other mediators of inflammation
where are silent nociceptors primarily found?
viscera
what do silent nociceptors respond to best?
inflammation
what is primary hyperalgesia?
increased sensitivity to noxious and non-noxious stimuli in the area immediately surrounding the primary site of damage due to a sensitization of the peripheral nociceptors
what is the main cause of primary hyperalgesia?
sensitization of peripheral nociceptors by chemical substances
where are the spinothalamic neurons located? what type of information do they relay?
- lamina I and V of dorsal horn 2. non-noxious sensory information conveyed by Aa and AB fibers 33. noxious mechanical sensory information conveyed by Ad fibers 4. noxious sensory information conveyed by C fibers
the spinothalamic neurons in which dorsal horn lamina are considered nociceptive specific?
II and III - receive only noxious input
what are wide dynamic range neurons?
spintothalamic neurons in lamina V that receive both non-noxious (Aa and AB) and noxious (Ad and C) input
what are the NTs for the primary afferent inputs (Ad and C)?
- substance P 2. glutamate 3. neurokinin A
glutamate activates what receptor(s) in the spinal neuron?
AMPA and NMDA
what allows glutamate to act on NMDA receptors?
substance P
what is the result of opening NMDA channels?
long lasting depolarization of post synaptic membrane, making neuron more easily excitable and opening voltage sensitive calcium channels (increasing sensitivity)
what is the wind up phenomenon?
increased neuronal sensitivity due to increased intracellular concentration of calcium, elaborating more AMPA and NMDA glutamate receptors
what is the proposed cause of secondary hyperalgesia?
change in responsiveness of spinothalamic neurons mediated by substance P and glutamate
definition: allodynia
pain resulting from a non-noxious stimulus, produced by facilitation of second order neuron responsiveness to non-noxious stimuli through the wind up or similar phenomenon elicited from intense noxious input
what responses are associated with the paleospiniothalamic tract?
increased arousal, affective and autonomic responses (affective motivation pathway)
what responses are associated with the neospinothalamic tract?
localization, quality, and type of pain (sensory discrimination pathway)
what areas of the brain are crucial and consistent sites for pain perception with regards to noxious stimuli?
- anterior cingulate gyrus 2. insular cortex
which area of the brain appears to be predominantly involved in producing anti-nociception (analgesia) by descending pain controlling mechanisms?
periaqueductal gray
what NT is used by the descending raphe system?
serotonin
what NT is used by the locus coeruleus?
NE
what is the gate control theory of pain?
- low threshold, faster conducted mechanoreceptor activation (Aa and AB fibers) enhances the activity of an inhibitory interneuron which reduces excitability of the pain conveying spintothalamic and spinoreticulothalamic projection neurons 2. Aa and AB input arrives at the inhibitory interneuron faster than Ad and C fibers
