10.24 Pain Flashcards
pain receptors are _____ nerve endings
free
do nociceptors adapt?
no
what is the axon reflex?
peripheral release of NT from the nociceptor (efferent function)
a non-noxious stimulus now begins to produce pain
allodynia
A noxious stimulus produces a larger response due to sensitization of nociceptors
hyperalgesia
what are the three types of pain nociceptors can sense?
mechanical
thermal
chemical
what types of pain do C fibers respond to? which one is unique?
mechanical
thermal
CHEMICAL
what types of pain do A-delta fibers respond to?
mechanical
thermal
what fibers correspond to the initial, sharp, well localized pain? what is this called?
“first pain”
A-delta fibers
what fibers correspond to the dull, diffuse, poorly localized pain that follows after? what is this called?
“second pain”
C fibers
axons of the pain and temperature enter the dorsal root entry zone more ________, while the touch and proprioception fibers are more _________
lateral
medial
the A-delta and C fibers branch into a fiber tract in the spinal cord called _________. What does this tract allow?
Lissauer’s tract
for the fibers to travel rostral or caudal for a few spinal cord segments
sensitization of sensory pain fibers means ________ thresholds
lower
____________ ___________ is when second order sensory neurons get sensitized. What does this contribute to?
central sensitization
hyperalgesia, allodynia
what are the two NTs associated with pain?
substance P
glutamate
what are the two endogenous peptides that produce pain relief?
endorphins
enkephalins
opioid receptors are found on ___________ fibers (in general)
nociceptive
what are the two thing opioid receptors do?
- open VG K+ channels, letting K+ leave the cell and thus hyper polarizing
- block VG Ca++ channels, preventing calcium entry into cell and blocking NT release
the descending fibers of the supraspinal descending system project along a tract called the:
dorsolateral funiculus
what is the descending modulatory system that originates in the periaqueductal gray (PAG)?
supraspinal descending system
where do neurons project in the descending pain modulatory system after the PAG?
locus ceruleus (pons) medullary reticular formation (medulla)
inhibition of a tonically active GABA neuron is called _____________. (this is what ______ receptors do in the descending modulating pain pathway)
disinhibition
opioid
what do the descending pain modulatory neurons release? what do they indirectly release?
5HT and NE
enkephalins and endorphins
mechanism of steroidal anti-inflammatory drugs
release lipocortin which inhibits PLA2, not allowing arachidonic acid to be mobilized from the lipid bilayer
