LO6 Temp and pain [8] Flashcards
(37 cards)
Temps outside which range elicits as pain? What is the thermoneutral point?
outside 10-48 C
33 = thermoneutral
Cold vs Warm receptor range
Cold: 10-37
Warm: 30-48
(note: 33 = thermoneutral point)
How is Temp information from periphery received?
Temp info from periphery →
transduced into receptor potential → trigger AP
(stronger intensity = more AP freq)
Cool receptors on free nerve endings of neurons are typically found on _____ fibers and warm receptors are found on ____ fibers
Aδ fibers - cool
C fibers
(note the switch:
- nociceptors that are activ. by extreme HOT temp (>43) are associated with Aδ fibers
- Nociceptors associated that signal extrememely COLD temp (
Difference between the spinothalamic tract and the spinoreticular tract
spinothalamic tract: carries info that provides conscious awareness of skin temp
SPinoreticular tract: carries info (ie pain) via reticular formation → forebrain/hypothalamus (imp for body temp control/autonomic fxn) → elicits emotional/behavioral response
The anterolateral pathway includes which tracts? List the structures that these tracts convey info to.
- spinothalamic
- thalamus - spinoreticular
- forebrain → medulla/pons - spinomesencephalic
- midbrain PAG
Two other cortical regions that are activated when pain info is processed (other than thalamus+forebrain+hypothalamus) and why they are imp.
- cingulate gyrus: part of limbic system → emotional component of pain sensation
- Insular cortex → processes info (autonomic component of pain)
The DRG is to the Trigeminal ganglion as the dorsal horn is to the _______
Spinal Trigeminal nucleus
only it receives input form the head/neck via trigeminal ganglion instead of trunk and limbs from DRG
Thermal nociceptors that are activated by extreme temps are associated with which fibers?
Cold?
Hot?
- nociceptors that are activ. by extreme HOT temp (>43) are associated with Aδ fibers
(note: Aδ for Hot and C for warm) - Nociceptors associated that signal extrememely COLD temp are associated with C fibers)
(note: Aδ for cool, C for Cold)
Intense pressure (not touch) activates which receptors?
mechanical nociceptors (which are assoc w/ Aδ fibers)
____ fibers for Hot and ____ fibers for warm
Aδ for Hot and C for warm
(remember the warm cunt?)
(Aδ fibers - cool and HOT)
____ fibers for cool, ____ fibers for Cold
Aδ for cool, C for Cold
C fibers - warm and COLD
Polymodal nociceptors have ____ fibers as their afferents.
What do they do?
C fibers
Polynodal nociceptors are activated by high intensity mechanical, chemical, or thermal stimuli.
Capsaicin activates nociceptors, how is it used as an analgesic?
Intense activation of capsaicin → massive secretion/depletion of Sub P
Stimuli that activates VR-1 receptor
VR-1 (capsaicin rcptr) strongly activated by capsaicin and weakly activated by acids and moderate heat (43 C)
- the VR-1 rcptr is part of an ion channel complex: Rcptr is activated → NSC channel opens → depolarization
Where is the VR-1 receptor located?
Expressed on Polymodal nociceptors (that have C fibers as their afferents)
Order of pain for Aδ fibers and C fibers
First pain: Aδ fiber
- tolerable, localized, prickling pain
- smaller receptive fields allows for more localization
Second pain: C fiber
- slower, burning, intolerable pain
- larger receptive fields: poorly localized pain
Out of all of the fibers, which one would get activated first with high pressure? higher pressure than that?
The most metabolically active ones
- so if you rub your arm w/ high P → activate larger Aα and Aβ fibers ( non nociceptive afferent pathways, which leads to activation of dorsal horn interneurons that inhibit synapses activated by nociceptive fibers.
- at higher P than that, C fibers also activated
Out of all of the fibers, which are the ones to become activated first?
- which ones get activated with small shock? larger shock than that?
larger Aα and Aβ fibers
(these ones activated first are also the first ones to be blocked with P first - (not drugs))
- this results in sensations of touch, vibration, joint movement - all without pain
- larger shock → prickling pain → even larger shock → BURNING pain (C fibers)
Out of all of the fibers, which are the ones to become nonconductive first with low dose anesthetics? Med dose? High dose?
anesthetics preferentially block small diameter fibers (C fibers - burning pain)
higher dose: block prickling pain
Higher dose than that: touch, afferents, motor axons (paralysis)
(Note: The order that they are blocked are opposite from that of how they get activated with shock)
Activators of nociceptors
BK
K+
Acid
5-HT
= pain producing agents
Sensitizers of niceptors
ATP ACh PG Sub P 5-HT
-Sensitizer in that it lowers threshold for nociceptor activation = more pain = hyperalgesia
How does aspirin help with pain?
Inhibits COX → prevents synth of PG → prevents nociceptor SENSITIZATION
Allodynia
Extreme sensitization
lowered threshold
