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Physiology 6600 > Peripheral Pain lecture > Flashcards

Peripheral Pain lecture Flashcards

1
Q

A delta fibers are nociceptive specific to what?

A

noxious mechanical stimuli

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2
Q

Describe A delta fibers’ roles.

A

1st pain, fast, sharp, and well-localized pain

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3
Q

C fibers are nociceptive specific to what?

A

mechanical, chemical, thermal and many polymodal stimuli

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4
Q

Describe C fibers’ roles.

A

2nd pain, slow, dull or burning, poorly localized pain

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5
Q

Which is more common as far as cutaneous nociceptors goes?

A

C fibers are far more common than A delta fibers. 87% to 13%

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6
Q

What are TRP receptors?

A

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

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7
Q

What is chemesthesis?

A

It is the response of c-fibers to chemical stimuli

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8
Q

What sensations are experienced in chemesthesis?

A

burning, tingling, astringency, pungency

IE salt water on an open wound or spicy food

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9
Q

The vanillin receptor (TRPV1 or V1) responds to what?

A

Capsaicin
Heat
Protons

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10
Q

What are the branches of the trigeminal nerve with prominent chemesthesis?

A 
In the nasal region- ethmoid branch (selective to smelling salts (ammonia))
In the oral region-
Posterior palatine
Nasopalatine
and Lingual nerves
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11
Q

Chemesthesis is mediated by what?

A

TRP receptors

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12
Q

T/F the TRP receptors involved in chemesthesis have a low threshold for chemosensitivity?

A

False- they have a high threshold chemosensitivity

IE 2.5M NaCl for TRP in chemesthesis versus 0.01M NaCl for taste

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13
Q

What kind of sensations are associated with chemsthesis?

A

Mostly aversive sensations- burning and tingling for example, not banana flavored or salty

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14
Q

T/F chemesthesis are linked to removal reflexes like salivation, coughing, tearing up, or sneezing?

A

Truth! If you swallow something really hot you may cough, salivate and your eyes may water

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15
Q

T/F nociceptors can exhibit desensitization? If not why if so, how?

A

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

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16
Q

What type of fibers are found in dentinal tubules?

A

A-delta fibers

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17
Q

What type of fibers are found in the pulp chamber?

A

C fibers

18
Q

T/f dentinal A fibers can respond to temperature?

A

Truth! This feels like sharp pain

19
Q

C fibers in the tooth pulp respond to what?

A

Respond to inflammatory mediators: they produce a dull/throbbing pain

20
Q

A delta fibers in the dentinal tubules respond to what?

A

Respond to mechanical, thermal, and chemical stimuli- all resulting in sharp pain

21
Q

If pressure is applied directly to dentinal tubules and the smear layer is intact or not intact, what is the result?

A

If intact smear layer, no pain

If not intact, pain results

22
Q

The stimulation of what type of fibers is responsible for sharp pain?

A

A delta

23
Q

What is hyperalgesia?

A

An increased sensitivity to pain. So a response to a non-painful stimuli can produce pain, pain can be spontaneous, pain can be prolonged

24
Q

In hyperalgesia, what happens in response to thermal or mechanical injury?

A 
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
25
Q

In hyperalgesia, what happens in response to damage that causes bleeding?

A

It has the same factors as thermal and mechanical stimulation as well as clot formation-bradykinin- which stimulates the c-fiber. Platelet products from the blood stimulate the c-fiber as well

26
Q

In hyperalgesia, what happens in response to damage that leads to infection and an immune response?

A

Prostaglandins sensitize the C fiber rather than cause direct excitation
Cytokines also sensitize the c fiber
Protons released in the inflamed tissue stimulate the vanilloid receptor and produce sensitization

27
Q

What is the result of sensitization of the c-fiber?

A

Pre sensitization, an afferent fiber may illicit a response due to mechanical stimulation at 9 grams.
AFTER sensitization, that same fiber may illicit a response at 1 gram of mechanical force. woa.

28
Q

T/F prostaglandins directly depolarize the neuron?

A

False, they do not

29
Q

Prostaglandins can block a potassium channel, helping an excitable cell reach the resting membrane potential faster so that it can be excited more quickly- it is now more sensitive.

A

Cool

30
Q

How does inflammation lead to a lower excitation threshold?

A
  1. The presence of inflammatory mediators
  2. Ca++ activated phosphorylation of TRPV1
  3. Increase in the number of receptors.
    Now the receptor is activated at 22 degrees celsius instead of the regular 42 C.
31
Q

For this lecture check out slide 42.. i think it’s important but am unsure how to organize it

A

you got it!

32
Q

Sensitization of ______ lowers the temperature threshold.

A

TRPV1

33
Q

Sensitization by _____ lowered the mechanical threshold.

A

prostaglandins

34
Q

If pain is spontaneous and prolonged, what is the cause?

A

The action of inflammatory mediators acts as peripheral stimuli

35
Q

What is causalgia?

A

Burning pain

36
Q

What is allodynia?

A

Light touch leading to pain

37
Q

What is sympathetic nerve dystrophy?

A

Temperature induced pain

38
Q

What are phantom sensations?

A

It is a sensation in a denervated tissue

39
Q

Nerve sprouting and collateral sprouting is sometimes painful.

A

ok

40
Q

C-fiber microneurography is where there is ectopic or abnormal discharge. What does this mean?

A

It means there is spontaneous activity, prolonged response to a known stimulus, initiation of a response from an atypical site

41
Q

C-fiber microneurography is a result of what?

A

An injury-induced increase in Na+ channels

42
Q

Nerve sprouting results in increased fiber density. Ectopic discharge can result, where the activity is not coming from where it should.

A

Excellent.

Physiology 6600 (10 decks)

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