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Physiology Test 2 > Somatosensory and Pain > Flashcards

Somatosensory and Pain Flashcards

1
Q

What are the two major subdivision of the somatosensory system?

A

Lemniscal and Anterolateral

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2
Q

Where are the cell bodies of the mechanoreceptors in the skin found?

A

The Dorsal Root Ganglia.

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3
Q

What does the lemniscal system consist of?

A

Discriminative/fine touch and pressure, vibration and proprioception.

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4
Q

What does the anterolateral system consist of?

A

Temperature, pain, crude touch, tickle and itch.

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5
Q

What two fibers innervate tooth pulp?

A

C and Adelta

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6
Q

What fiber has the smallest receptive field size, and modality is propioception?

A

Aalpha.

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7
Q

What type of fiber has the modality of fine discriminative touch/pressure?

A

Abeta.

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8
Q

What is fiber has the largest receptive field size and modality is temperature, and slow, dull pain?

A

C

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9
Q

What fiber has the modality of temperature and fast pain?

A

Adelta

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10
Q

What is a dermatome?

A

The receptive field of a dorsal root ganglion.

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11
Q

How did dermatomes get mapped out?

A

Due to Herpes zoster infection of trigeminal nerve roots and individual DRG, causing shingles.

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12
Q

What fibers are associated with thermal nociceptors?

A

Heat-A-delta

Cold-C fibers

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13
Q

What fibers are associated with mechanical nociceptors?

A

A-delta

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14
Q

What type of fibers are associated with polymodal nociceptors?

A

C fibers.

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15
Q

What are the two types of pain?

A

Tolerable, localized, pricking-A-delta. First Pain.

Burning, less tolerable, diffusely localized- C fiber-Second pain.

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16
Q

What is referred pain?

A

Pain impulses arising from different locations that which they originate. Think heart attack, or diseased internal organ.

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17
Q

What are activators? Give an example.

A

Lead to direct activation of nociceptors. Bradykinin. Strong-pain producing agent. A-delta and C fibers. Potassium, acid and serotonin can also act as activators.

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18
Q

What is sensitization? Give examples.

A

Lowers the threshold for pain. Less of a pain stimulus gets that nociceptors working. Prostaglandins and Substance P. C fibers release substance P during periods of repetitive electrical stimulation.

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19
Q

What is an example of something that acts both as an activator or a sensitizer?

A

Serotonin.

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20
Q

How does aspirin work?

A

Inhibits an enzyme which converts an acid into prostaglandin which is a sensitzer.

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21
Q

What is sensitization of nociceptors known as?

A

Primary hyperalgesia, bc the mechanism leading to the increased sensitivity to pain is at the first site of the pathway. Directly in the tissues.

22
Q

What is allodynia?

A

Sunburn. When sensitization is extreme enough to allow non-noxious stimuli to trigger a painful sensation.

23
Q

What does the triple response consist of?

A

Reddening, wheal and flare.

Result of an injury.

24
Q

What molecule plays an important role in the triple response? What leads to it’s production?

A

Bradykinin. Tissue damage. Acts as an activator.

25
Q

What else does bradykinin act as in the the triple response other than an activator?

A

Vasodilator (heat and redness) and increased permeability of capillary membranes (leading to edema/wheal/swelling and fluid accumulation)

26
Q

What is the pink-colored zone around the inflamed area called?

A

Flare.

27
Q

What mechanism underlies the production of the flare?

A

The “axon reflex”. The large receptive fields of C-fibers is activated by bradykinin. Action potential from the depolarization will propagate in 2 directions: Cell body and more peripherally in the collateral terminals in neighboring skin regions. Substance P and CGRP are released in a region surrounding the wound inducing a milder vasodialation.

Flare region is sensitized by substance P and sometimes can create allodynia.

28
Q

Where do C fibers terminate?

A

In the substantia gelatinosa of the dorsal horn.

29
Q

What do neurons in the dorsal part of the spinal cord process?

A

Sensory information.

30
Q

Where to nociceptive afferent fibers form synapsis in the head and neck and the trunk and limbs?

A

Spinal trigeminal nucleus and the dorsal horn of the spinal cord (trunk and limbs)

31
Q

The afferent fibers enter on the ________ ________ as the initial site of sensory transduction.

A

same side

32
Q

What does modality segregation allow for?

A

Different second-order cells to process simultaneous information associated with each sensory modality.

33
Q

What are the different regions of the dorsal horn known as?

A

Laminae.

34
Q

What is the major excitatory transmitter released by primary nociceptive sensory neurons at the site of the first synapse in the dorsal horn?

A

Glutamate.

35
Q

What are the 2 types of glutamate receptors? What kind of receptors are they?

A

AMPA and NMDA. Ionotropic (directly coupled to an ion channel)

36
Q

How do the time course of the AMPA and NMDA receptors differ?

A

AMPA is rapid. NMDA slower and requires both glutamate and depolarization.

37
Q

Which glutamate receptor gets activated first?

A

AMPA. There is only glutamate present at first. If there is consistant C fiber stimulation, it leads to a post-synamptic stimulation and a depolarization….THEN NMDA gets activated.

38
Q

What is wind up?

A

A form of central sensitization. It is the stimulation dependent enhancement of the post-synaptic response of pain activated dorsal horn neurons. (NMDA and AMPA)

39
Q

What does phosphorylation of the NMDA receptor do?

A

Removes the requirement for depolarization to activate it. Long lasting changes in excitability.

40
Q

What does substance P do in the CNS?

A

Leads to enhancement and prolongation of the actions of glutamate, by binding to the receptor, closing K channels and leading to depolarization.

41
Q

What is neuropathic pain?

A

Damage to either the peripheral or CNS that leads to persistent pain syndroms.

42
Q

Peripheral mechanism

A

Pain in the absence of any stimuli. Affects the sodium channels an leads to a discharge of primary pain afferents.

43
Q

Central Mechanisms

A

Sprouting and Rewiring. Pain activated inappropriately at the level of the dorsal horn synapse A beta fibers invade substantia gelatinosa normally occupied by C fibers.

44
Q

What is analgesia

A

Central modulation of pain.

45
Q

What are the two mechanisms of analgesia?

A

Gate control and descending control.

46
Q

What is the gate control theory of pain modulation?

A

Dorsal Horn Synapse: reflects a balace between nociceptive and non-nociceptive inputs.

47
Q

How does rubbing an area help pain?

A

Activates the A beta touch fibers that leads to activation of dorsal horn interneurons that in turn inhibit synapses activated by nociceptive fibers.

48
Q

What is TENS?

A

Transcutaneous Electrical Nerve Stimulation. Electrodes are used to stimulate large-diameter fibers that are in that area. Decreases the efficacy of nociceptive dorsal horn synapses.

49
Q

How is acupuncture believed to worK?

A

Reduce pain by activating the large diameter mechanosensory afferents.

50
Q

What is the decending control?

A

Periaqueductal gray region. PAG. Stimulate it. In the midbrain. Touch, pressure and temp persist. only pain is attenuated. Stimulation produced analgesia.

51
Q

How does the descending control work?

A

neurons in the medulla use serotonin as their NT. Serotonin inhibits of 2nd order neurons of the dorsal horn by exciting an inhibitry interneuron. the inhibitory neuron presynaptically blocks the voltage gated Ca curren and postsynapticaly opens K vhannels.

52
Q

What type of receptors are opiate receptors?

A

g protein coupled receptors. Activation leads to inhibition of the neuron on which they are found. PAG is specificallly sensitive.

Physiology Test 2 (4 decks)

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