Peripheral Pain lecture Flashcards
A delta fibers are nociceptive specific to what?
noxious mechanical stimuli
Describe A delta fibers’ roles.
1st pain, fast, sharp, and well-localized pain
C fibers are nociceptive specific to what?
mechanical, chemical, thermal and many polymodal stimuli
Describe C fibers’ roles.
2nd pain, slow, dull or burning, poorly localized pain
Which is more common as far as cutaneous nociceptors goes?
C fibers are far more common than A delta fibers. 87% to 13%
What are TRP receptors?
They are a large family of receptors that are involved in transducing chemical and thermal nociception
Also involved in non-noxious thermal transduction
Also found on odontoblasts- possible role in tooth pain
TRP receptors are found on trigeminal sensory fibers respond to chemicals t immediate chemesthesis
What is chemesthesis?
It is the response of c-fibers to chemical stimuli
What sensations are experienced in chemesthesis?
burning, tingling, astringency, pungency
IE salt water on an open wound or spicy food
The vanillin receptor (TRPV1 or V1) responds to what?
Capsaicin
Heat
Protons
What are the branches of the trigeminal nerve with prominent chemesthesis?
In the nasal region- ethmoid branch (selective to smelling salts (ammonia)) In the oral region- Posterior palatine Nasopalatine and Lingual nerves
Chemesthesis is mediated by what?
TRP receptors
T/F the TRP receptors involved in chemesthesis have a low threshold for chemosensitivity?
False- they have a high threshold chemosensitivity
IE 2.5M NaCl for TRP in chemesthesis versus 0.01M NaCl for taste
What kind of sensations are associated with chemsthesis?
Mostly aversive sensations- burning and tingling for example, not banana flavored or salty
T/F chemesthesis are linked to removal reflexes like salivation, coughing, tearing up, or sneezing?
Truth! If you swallow something really hot you may cough, salivate and your eyes may water
T/F nociceptors can exhibit desensitization? If not why if so, how?
True
Through intense or repeated stimulation the nociceptors can become less responsive via different mechanisms. IE inactivation of voltage gated ion channels or depletion of neuropeptides
What type of fibers are found in dentinal tubules?
A-delta fibers
What type of fibers are found in the pulp chamber?
C fibers
T/f dentinal A fibers can respond to temperature?
Truth! This feels like sharp pain
C fibers in the tooth pulp respond to what?
Respond to inflammatory mediators: they produce a dull/throbbing pain
A delta fibers in the dentinal tubules respond to what?
Respond to mechanical, thermal, and chemical stimuli- all resulting in sharp pain
If pressure is applied directly to dentinal tubules and the smear layer is intact or not intact, what is the result?
If intact smear layer, no pain
If not intact, pain results
The stimulation of what type of fibers is responsible for sharp pain?
A delta
What is hyperalgesia?
An increased sensitivity to pain. So a response to a non-painful stimuli can produce pain, pain can be spontaneous, pain can be prolonged
In hyperalgesia, what happens in response to thermal or mechanical injury?
The c-fiber responds and releases substance P or CGRP Substance P (SP) stimulates mast cells which release histamine and then further stimulate the c fiber. CGRP causes vasodilation and swelling which acts as a mechanical stimulus to the c-fiber
