Section 3 Pain Flashcards
The detection and localization of a stimulated pain receptor:
nociception
The emotional (affective) and arousal aspects of such stimulation:
pain
T or F? Pain and temperature are transmitted along different pathways.
F. same pathway
T or F? All thermoreeptors are specialized for non-noxious temperature ranges.
F. Some (same for noxious)
Temp range bw 50’ and 140’ stimulates:
TRPA1, M8, V4, V3, V3, TRPV1, TRPV2 (low temp to high temp)
At what temp do thermoceptors plateau out?
after 140’
Fire at a high rate of increase at the 45’ C range:
TRPV1
Fire at a high rate of increase at 50’ C:
TRPV2
Fire at a higher rate at decreasing temperatures:
TRPV4, TRPM8, TRPA1
How do thermoceptors respond to increasing temps?
by changing their conformation
TRPM8:
increases firing as things get cool and activated by menthol
Why is menthol cool?
transmitted via TRPM8, temps under 25 ‘C
Which are activated by capsaicin:
TRPV1 fibers, active as it gets hotter normaly, 45’ C
Medical tx using capsaicin:
arthritis ointment, gradually hyperactivates nociceptor axons, depleting its NT (substance P) and blasts them out, making nonfxnal, TRPV1
What is the NT for arthritis?
Substance P
A-delta nocioceptors:
thinly-my, fast conducting, fast pain (sharp, prickling, localized)
C nocioeptors:
unmy, slower conducting, slow pain (diffuse, burning)
A nocipceptor that responds to all types of stimuli:
polymodal (therm, mechanical, heat and cold)
Localized response to stepping on a tack, and then diffuse later:
differentiation comes bc we have 2 types of fibers that transmit at different rates
What activates nocioceptors?
Heat, cold, mechanical, chemical
T or F? Some nociceptors respond to only one type of stimulus.
T
What gives rise to the inflammatory soup?
Damage cells leak contents which activates the nocio endings giving rise to the inflammatory soup
Contents of the inflammatory soup:
ATP, serotonin (5-HT), histamine, bradykinin, H+, prostaglandins
Reduce pain by taking:
an aspirin, reduces prostaglandin production
What does tissue damage lead to?
the release of substances that activate nociceptors
What is 5-HT?
Serotonin
Both aspirin and IB profin block:
COX-2
Which is more selective, aspirin or Ibuprofen?
Ibuprofin
Pwy from tissue damage to pain:
Cut, arachidonic acid, COX-2, prostaglandins, pain
Ibuprofin only blocks:
COX-2
Aspirin blocks:
both Cox-1 and Cox-2
Blocking Cox-1 is associated with?
GI symptoms
Selectively blocks pain and not other sensations:
Analgesic
Anesthetics block:
non-selectively, not just pain
Lidocaine blocks:
voltage gated Na channels, blocks all n. conduction, unable to move nearby mm. as well)
Name an analgesic.
Aspirin
T or F? APs can’t invade non-stimulated nociceptor branches.
F. they can
What NT increases activation of nearby nocioceptors?
Histamine
How can pain lead to edema and more pain?
APs invade non-stimulated branches, nociceptor endings release Sub P and CGRP (calcitonin Gene-Related Peptide), Sub P activates mast cells, macros, and neutrophils, which release pain producing substances. CGRP and SubP cause vasoldilation, plasma leaks out, including bradykinin, edema and more pain
Increased sensitivity to painful stimuli:
hyperalgesia (prone to heightened pain if area has already been hurt (soup and other aspects of CNS)
Pain due to a stimulus that deos not normally provoke pain:
allodynia
Painful, inflammatory condition usually caused by carious bacteria penetrating dentin:
pulpitis
Early events in inflammatory pain:
vasodilation, inc interstitial fluid P, pain
Early symptoms of pulpits:
hypersensitivity of tooth (cold, hot evoke a stab of short lasting pain)
Type of receptors peripheral neurons have:
Opioid
Major source of peripheral opioids:
Immune cells
Endorphins:
bind receptors in the brain
“endorphin” stands for:
Endogenous morphine
Types of endorphins:
enkephalins, endo(mo?)rphins, dynorphins
Endogenous opioid receptors:
delta-OR, kappa-OR, mu-OR, nociceptin/orphanin FQ peptide receptor
Synthetic ligands for ORs:
codeine, oxycodone, morphine, heroin, methadone, usually similar to opium
Effects of peripheral opioid receptors:
Change levels of 2nd msgs (i.e. cAMP), reduce Ca channel opening, cell depolarizes, Sub P, CGRP, and other nasty things leak out. Less Na channel opening, leads to less pain conduction to CNS
What differentiates pain fibers from others?
Na channel type (1.8 and 1.9 for damage sensing?) for AP transmission to s.c. (sometimes overexpressed making the axon hyperexcitable)
What may develop after traumatic damage to a peripheral nerve?
causalgia, improper n. regeneration, excess Na channels, easier to generate APs even wo pain stimulus
T or F? Strong analgesics can tx causalgia.
T. ish. Sometimes not enough
Hypothesized mechanism of causalgia:
upregulation of Na channels
How does an Inflamed nerve differ from a normal nerve?
less my, more voltage sensitive Na channels, easier to get APs when they should be firing, cross-talk, new kinds of Na channels can appear
What starts to get expressed in pulpits?
New kinds of Na channels on my polymodal A-delta fibers
What happens to my polymodal A-delta fibers if they start to loose their my?
cross-talk
What controls how much pain info reaches consciousness?
Descending projections
What can lead to hypersensitivity to pain or the damping down of pain?
Local changes in the s.c.