EX1; Peripheral Pain Flashcards
This type of pain is short term with an identifiable source
acute pain
This type of pain is long term frequently with a non-identifiable source
chronic pain
This type of fiber makes up roughly 13% of cutaneous nociceptors, while this fiber makes up roughly 87%
13%; A-delta
87%; C fibers
Which fiber is tiny (0.2-1.5µm) and is unmyelinated and which one is small (1-5µm) and is lightly myelinated
tiny/unmyelinated = C small/myelinated = Adelta
Which fiber has a faster conduction velocity (12-36m/s) compared to 0.5-1.2m/s
Adelta is faster than C
Which fiber has neuropeptides (but limited)
Adelta
Which fiber has its Na channels both TTX-sensitive (typical) and TTX-r (sensory-nerve specific)
C fibers
A delta is just mainly TTX-sensitive (typical)
What are the response properties of A delta fibers
noxious mechanical stimuli
some noxious heat
chemical stimuli; inflammatory mediators but not capsaicin
What are the response properties of C fibers
varied stimuli buy many POLYMODAL (but all noxious)
What is the TRPV-1/2 expression for Adelta and C fibers
A delta; TRPV-1 expression is rare, TRPV-2 more likely
C fibers; many express TRPV-1
This fiber is the first pain, fast, sharp, and well localized
A delta
This fiber is 2nd pain, slow, dull or burning, poorly localized pain
C fibers
These channels may play a role in mechanical nociception; very speculative
ENaCS (epithelial sodium channels)
This is a large family of receptors transducing chemical and thermal nocicpetion (possibly mechanoreception)
transient receptor potential (TRP)
TRP receptors are also involved with the is type of transduction
non-noxious thermal transduction
TRP receptors found here respond to chemicals to mediate chemesthesis
trigeminal sensory fibers
TRP receptors are also found here; with a possible role in tooth pain
odontoblasts
C-fibers innervating the oral and nasal mucosa have a small receptive field and what kind of chemorecpetive properties
polymodal
Specialized ending and chemesthesis allow for an important distinction between what
taste and olfaction
The response of trigeminal C-fibers that signals pain and sensations associated with what
spicy food; capsaicin
burning and tingling
This term means no olfactory sensation
anosmic
A large proportion of polymodal c-fibers and a few a-deltas are sensitive to what
capsaicin
Vanilloid receptor (TRPV1 or V1) responds to what three things
capsaicin
heat (42°C)
protons
stimulations of vanillin receptors results in what
the influx of cations (Na and Ca)
What are the branches of the trigeminal nerve with prominent chemesthesis
nasal; ethmoid (smelling salts)
oral; posterior palatine, nasopalatine, lingual nerve
Is chemesthesis high or low threshold chemosensitivity
high
What is the predominate type of sensation of chemesthesis
aversive; burning, tingling
Chemesthesis also plays a role in “removal” reflexes such as what
salivation
coughing
tearing
sneezing
Chemesthesis can also be activated by two other things
dental compounds
drugs (capsaicin compounds) for pain treatment
These fibers are found 0.1-0.2mm into dentinal tubules and are associated with sharp pain
a-delta fibers
The a-delta fibers of dentinal tubules contain what, associated with mechanical and thermal sensitivity, also chemical stimuli like NaCl.
calcitonin gene-related peptide (CGRP)
These fibers are found in the tooth pulp and contain substance P; initiating a dull, throbbing pain
c fibers
What kind of sensitivity do c-fibers respond to
thermal sensitivity
chemosensitivity to inflammatory mediators (bradykinin)
This theory holds that despite the lack of innervation of the DEJ, this area is sensitive to mechanical, thermal, and chemical stimuli causing fluid to flow in the tubules
hydrodynamic theory
Fluid flow of the hydrodynamic theory causes what to occur, stimulating a response
the fluid flow causes distortion in proximal parts of dentinal tubules where the sensory endings are located, thus stimulating the receptor
What evidence supports the hydrodynamic theory of pain
noxious temperature was applies to dentin and subjects reports of pain were directly correlated between the integrated nerve activity (INA) and increased pain response (PAS), since the pain was described as “sharp” this indicates that they are a-delta fibers of which are found in the tubules
This is extremely important in the transduction process involving the hydrodynamic theory, when this was removed, subjects experienced pain
smear layer
What are the three major characteristics of hyperalgesia
- greater responsiveness to stimuli (both nociceptive and low-threshold)
- pain is spontaneous in occurrence (lack of obvious stimulus)
- pain is prolonged
Interactions between what things can induce hyperalgesia
interactions between different neural systems (afferent/efferent(
interactions between nervous and non-nervous cells
This stimulates nociceptors to secrete substance P which in turn releases histamine, in turn, re-stimulates nociceptor
thermal or mechanical injury
Histamine also promotes these two things which can further act as a mechanical stimulus on nociceptors
vasodilation plasma extravasation (swelling)
This results in the release of bradykinin which stimulates nociceptors and further result in stimulation of histamine release from mast cells
bleeding
This results in leukocyte products such as prostaglandins sensitize cells rather than directly stimulate them to produce action potentials
infection
Many of cells involved in an inflammatory reaction release factors that are either these three things
algesics
stimulate other cells to release factors that are algesics (subP stimulates mast cells to release histamine)
do not directly stimulate nociceptor neurons but are involved in the process of sensitization
This is something that directly stimulates nociceptor cells
algesics; like bradykinin
The vanilloid receptor undergoes this, by becoming more sensitive to heat and capsaicin after protons are released in an inflamed area; more sensitive (22 degrees instead of 44) to other stimuli now
hyperalgesia
C-fibers contain this, which unlink A fibers, require greater depolarization thus leading to a higher threshold
TTX-insensitive sodium channels
C-fibers have small conductance K channels that function to do what
prolong the period of hyperpolarizaion following an action potential; thus producing fewer action potentials per unit of depolarization compared to A fibers
The K channels in C fibers can be blocked by what, thus returning the membrane potential of transmitting painful signals; “sensitized”
prostaglandins
This is a burning pain associated with nerve damage
causalgia
This is light touch leading to pain associated with nerve damage
allodynia
This is temperature induced pain associated with nerve damage
sympathetic nerve dystrophy
This is sensation in denerved tissue associated with nerve damage
phantom sensations
This type of change is toward the cell body; such as ganglion cell death if the axon is cut near the cell body
retrogrades chages
If cell death does not occur, the cell body can undergo this, which the cell swells and the nucleus moves to an eccentric position and the RER moves to the side
chromatolysis
Chromatolysis is a historical marker for what
damages or injured cell and is associated with increases protein synthesis in response to repair or injury
True or False
Increased protein synthesis of a damaged nerve can lead to changes in cell properties like if more channel proteins are made, then that cell may become more sensitive to new things also due to lack of myelin
True
Damage to the axon can result in this, in which the axon process heading towards the CNS degenerates
transganglionic degeneration
This can occur in which the neuron contacted centrally by the axon dies
transneuronal degeneration
What are two anterograde changes associated with nerve injury
terminal degeneration of axon terminal
wallarian anterograde degeneration of axon
These in the vicinity of the lesion proliferate and produce ECM that provides substrate for regenerating axon
Schwann cells
This phenomenon is most likely to occur when an axon fails to regenerate; a surviving axon may grow new terminals into the area previously occupied by the other sensory cell
sprouting
Can sprouting have functional significance?
yes, has been indicated in a human subject
These can form which reflect the regenerative capacity of injured nerves; it is anatomically characterized as a tangled complex, disorganized web of neural tissue, leading in some instances to painful conditions when palpated or arising spontaneously
neuromas
An up regulation of Na channels makes for increased excitability and this, which is when a neuron responds, not from its receptor ending, but from stimulation of the cell body or axon
ectopic discharge
What two phenomena can cause pain in an neuroma
sprouting; fibers with central connections that signal pain (nociceptor stimulation)
ephaptic; (non-synaptic) connections between neurons in neuroma such that low threshold mechanoreceptors now activate pain fibers
This is when a neuron responds to action potentials from nearby neuron; could account for allodynia and referred pain
ephaptic
