travers- peripheral pain Flashcards by asw asw

what are the dimensions of pain?

1) Acute vs. Chronic
2) Sensation of pain vs affective component
3) “Normal” vs Pathological Pain

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what is the difference between pain sensation and the affective component?

sensation= Localization and intensity

affective component= Emotional response (psychological component)

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how is “normal” pain mediated? how is pathological pain mediated?

“normal” pain- A-delta and c-fiber mediated

pathological pain- Peripheral & central sensitization

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basic characteristics of A-delta fibers:

makes up 13% of cutaneous nociceptors

Small & lightly myelinated

responds to noxious mechanical stimuli

its the “1st pain- sharp and localized”

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basic characteristics of C fibers

makes up 87% of cutaneous nociceptors

tiny & unmyelinated

responds to varied stimuli, many POLYMODAL (but all noxious)

its the “2nd pain- slow, dull or burning, poorly localized”

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Both ______ channels and _____ receptors play a role in Pain transduction

ENaCS :(epithelial sodium channels)

TRP (transient receptor potential) receptors

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T/F: Some “Pain”/nociceptor TRP channels also have Chemosensitivity

true

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Chemesthesis is the response of _______ to chemical stimuli

c-fibers

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what sensations are associated with chemesthesis

Burning & tingling

e.g.
salt water on an open wound
Chili peppers in food (capsaicin)

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what does the Vanilloid Receptor (TRPV1 or V1) respond to? what does it trigger?

Responds to:

1. capsaicin
2. heat (42 degrees C)
3. protons

stimulation results in influx of cations (Na+ and Ca2+)

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which branches of the Trigeminal nerve contains prominent chemesthesis sensation?

Nasal branch:
1) ethmoid

Oral branch:

1) Posterior palatine
2) Nasopalatine nerve
3) LINGUAL NERVE

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Chemesthesis is Mediated by ______ receptors

TRP

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Chemesthesis predominately transmits ______ sensations

aversive

e.g. burning, tingling
probably not “banana” or “salty”

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dentinal tubules are occupied by which type of nerve fibers? What type of sensation are they responsible for?

A-delta fibers

contain calcitonin gene related peptide (CGRP)
mechanical & thermal sensitivity
sharp pain

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the pulp chamber is filled with which type of nerve fiber? what sensation is it responsible for?

C fibers

contain Substance P (SP)
thermal sensitivity
chemosensitivity to inflammatory mediators
dull throbbing pain

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within the tooth, _______ fibers respond to algesic stimuli such as bradykinins

C fibers

-has a long latency

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which dentinal fibers respond to temperature?

Dentinal A-fibers AND C-fibers can Respond to Temperature

The sensation from this stimulation is sharp pain in the dentin tubules, throbbing pain in the C-fibers

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high pressure applied to dentinal tubules does not cause pain, unless what happens?

EDTA dissolves smear layer

THEN pressure causes pain

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T/F: there is communication between odontoblasts

and nerve terminals

False

Communication has not been demonstrated

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what is the physiological evidence that supports the hydrodynamic theory?

A-delta fibers respond to mechanical, thermal,osmotic stimuli

Odontoblast may act as mechanoreceptor cell

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what are the characteristics of Hyperalgesia?

greater responsiveness to stimuli
pain is spontaneous
pain is prolonged

what is allodynia?

response to non-painful stimuli produce pain

___________ Mediators Affect Nociceptive Neurons

Inflammatory Mediators

which inflammatory mediators directly stimulate nocioceptors?

histamine
bradykinin
5-HT

which inflammatory mediators stimulate other cells to release algesics?

substance P: (from the nociceptor itself) stimulates histamine release bradykinin: increases histamine release (mast cells)

_________ are inflammatory mediators involved in sensitization

prostaglandins

how does inflammation increase the sensitivity of the Vanilloid Receptor (TRPV1 or V1)

1. Ca++ activated phosphorylation of VR1 receptor (TRPV1) 2. Increase in receptor number 3. Presence of inflammatory mediators (e.g.bradykinin & protons)

Sensitization of TRPV1 lowers the ___________ threshold

temperature

Sensitization by prostaglandins lowers the ___________ threshold

mechanical

Pain Pathophysiology associated with Nerve Damage:

1) Causalgia 2) Allodynia 3) Sympathetic nerve dystrophy - temperature induced pain 4) Phantom sensations - sensation in denervated tissue

Neuromas are caused by what?

collateral sprouting of nerve branches | can be painful

what are the characteristics of C-fiber ectopic discharge?

A) Spontaneous activity B) Prolonged responses to known stimulus C) Initiation of response from atypical site **Results from injury-induced increase in Na+ channels

Ephaptic Transmission is a mechanism for which 2 conditions?

mechanism for allodynia and referred pain

what are the mechanisms for peripheral sensitization?

- Decreased threshold - Pain is spontaneous & prolonged - Ectopic discharge – (abnormal activation)

what is the mechanism for ectopic discharge?

more Na+ channels following nerve injury response to catecholamines following nerve injury Ephaptic response due to increased Na+ expression

_________ will increased number and type of receptors after nerve damage

demyelination

T/F: Chemesthesis has a higher threshold for chemosensitivity than our sense of smell

true

what is chemesthesis mediated by?

TRPV1 (V1) receptors

Pain Perception Varies with ___________ Density

innervation

what is TRPV1 sensitive to? What about TRPA1?

TRPV1: - capsaicin - noxious heat (above 42 degrees C) - protons TRPA1: mustard oil, wasabi, garlic, noxious cold

Lingual Chemesthesis (common chemical taste) is sensed by what type of fibers?

Trigeminal polymodal nociceptors (c-fibers)

TRP receptors found on trigeminal sensory fibers respond to chemicals by mediate _________

chemesthesis

what types of ion channels are found in the odontoblast?

1.TRP channels (TRPM3 and TRPV4) sensitive to mechanical stimulation 2. Voltage-gated Na+ channels (odontoblasts can generate action potentials)

what neuropeptides do c-fibers release during thermal or mechanical injury?

releases neuropeptides substance P (SP) or CGRP

T/F: Prostaglandins can stimulate a neuron

FALSE- Prostaglandins do not stimulate neuron | they lower its threshold to stimuli- sensitize the neuron

what is the effect of CGRP being released from c-fibers?

vasodilation and swelling (mast cell activation) from a mechanical activation of C-fibers

_______ will stimulate c-fibers after an injury that causes bleeding

Bradykinin

there is a upregulation of Na+ channels following what?

nerve damage sprouting

how can the threshold limit for a nerve cell be lowered?

TRPV1- temperature threshold lowered by inflammation Prostaglandins lower mechanical threshold via SK K+ channels

which type of C-fiber will respond to only 1 type of nociceptive stimuli: e.g. chemical, or thermal or mechanical only

non-polymodal

what are trigeminal polymodal nocioceptors (c-fibers) sensitive to?

- different spices | - high concentrations of salt