L17: The Medial Pain System & Limbic-Motor Interactions Flashcards

1
Q

Explain the differences btw nociception & pain.

A

nociception = “sensation” -process that is associated with a noxious stimulus

pain = “conscious,” “emotional” -subjective experience associated w/ noxious stimuli

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2
Q

List the 5 main functions of medial pain system

A

a. limbic & autonomic activation (indirect ALS)
b. learning & anticipation (connections with amygdala & thalamus)
c. nocifensive behavior (medial premotor areas)
d. empathy (lateral nociceptive & medial pain systems )
e. inhibition (activate PAG & ACC)

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3
Q

In neuroanatomy, we learned about the anterolateral system carrying protopathic sensations (pain, temp, crude touch). The anterolateral system actually has 3 pathways, which are?

A

1 - direct anterolateral pathway –> pain, temperature, simple tactile sensations

2 - Indirect anterolateral pathways –> limbic, autonomic, endocrine & activation of pain inhibitory circuits

3 - posterior medial pathways –> visceral nociceptive info & conveys T, pain, irritation, chemical changes & stretch from visceral organs.

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4
Q

List the 3 main ascending spinal pain systems and the tracts that are associated with them.

A

1 - direct anterolateral pathway: neospinothalamic tract

2 - indirect anterolateral pathways:

a. paleospinothalamic tract
b. spinoreticular tract
c. spinomesencephalic tract
  1. posterior medial pathway
    • *these receptors have poor localization, thus the phenomenon of referred pain
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5
Q

What kind of surgery can be performed for chronic, debilitating, intractable visceral pain?

A

myelotomy/cordotomy of the posterior midline.

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6
Q

The major pt regarding the indirect ascending pain pathways (paleospinothalamic, spinomesencephalic, spinoreticular) is their connections support limbic/ANS activation, which is the 1st major function of medial pain system. Where are some of their projections and what impt 6 structures do they innervate?

A

-projections to RF, LC, midline & intralaminar thalamic nuclei (MITN) & PAG innervate:
1. nucleus ambiguous (breathing & HR)
2. gigantocellular RF that projects to sympathetic IML
3. parabrachial nucleus
4. PVN of hypothalamus
5. amygdala
6 -ACC

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7
Q

What is the 1st major function of medial pain system?

A

Limbic/ANS activation, which is achieved by the indirect ascending pain pathways.

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8
Q

Reticular formation is found thru out brainstem. What are the 4 impt nuclei of RF?

A
  • raphe nucleus (5-HT)
  • Locus Coerulus (NE)
  • parabrachial area
  • nucleus gigantocellularis
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9
Q

Mesencephalic & rostral pontine RF vs caudal pontine & medullary RF have different functions.

A

Midbrain & rostral pons –> modulating forebrain activity

Caudal pons & medulla –> premotor coordination of lower somatic & visceral motor neuronal pools

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10
Q

RF & PAG regulate ANS via projections to which 3 nuclei?

A
  • nucleus tractus solitarus
  • Dorsal motor nucleus of vagus
  • IML

**will modify autonomic functions (HR, BP, etc) in response to pain

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11
Q

An expt was conducted where a noxious stimulus was applied to hand. Patient was asked to “rate the unpleasantness” (the feeling of pain) and then to “attend to the location” (nociceptions). What did the results conclude about if pain and nociception are activating the same or different regions of the brain?

A

When asked to rate “unpleasantness,” the ACC & PAG (medial system) was activated.

When asked to attend to the location of the noxious stimulus, the MCC & thalamus are activated (lateral system).

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12
Q

What structures are involved in the medial and lateral systems and state whether pain or nociception is involved?

A

Medial System = ACC + PAG –> feeling of pain

Lateral System = MCC + thalamus –> nociception

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13
Q

The 2nd major function of the medial pain system is anticipation/learning. What is it?

A

Anticipation/learning is a form of associative learning in which a sound is associated with inflicting pain. Once, the person hears the sound, the brain is anticipating the pain stimulus. This depends on connections with amygdala & thalamus.

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14
Q

The 3rd major function of the medial pain system is nocifensive behavior. Which areas in the brain initiate nocifensive behavior?

A

medial premotor areas (SMA-supplementary motor areas & Cingulate motor areas) when activated will prime motor system to initiate nocifensive behaviors.

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15
Q

So far we’ve mentioned limbic/ANS activation, anticipation/learning, and nocifensive behavior as important functions of medial pain system. Another is pain empathy. Explain what this will activate.

A

seeing pain inflicted on others will activate many lateral nociceptive & medial pain systems & can evoke similar emotions.

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16
Q

What is the last resort treatment for debilitating chronic pain? After the procedure, what can the patient feel?

A

Anterior cingulotomy is a last resort treatment for debilitating chronic pain. Patient will still feel the pain, but doesn’t care about it because will abolish nocifensive behavior & many limbic/autonomic responses.

17
Q
  1. Limbic/ANS activation
  2. anticipation/learning
  3. Nocifensive behavior
  4. pain empathy
    What is the last major function of the medial pain system that we talked about in class?
A
  1. pain inhibition

- it is experimentally shown that stimulating medial area near motor cortex will relieve pain, and activate PAG & ACC.

18
Q

Experimentally, what do you expect when you give opiate placebo analgesia?

A

effective placebo effect activating the ACC

19
Q

Can medial pain system modify subjective experience of pain?

A

Yes, there are many functions of medial pain system that can modify subjective experience of pain (limbic/ANS activation, anticipation/learning, nocifensive behavior, pain empathy, pain inhibition)

20
Q

What is mental-stress-induced analgesia (SIA)?

A

relies on medial pain system & descending pathways, involves opiod & non-opiod mechanisms.

for ex: Pt while given noxious stimuli & asked to perform mental math (mental stress) will have increased pain tolerance.

21
Q

What occurs during central pain sensitization to chronic nociceptive input?

*Central sensitization is a condition of the nervous system that is associated with the development and maintenance of chronic pain. When central sensitization occurs, the nervous system goes through a process called “wind-up” and gets regulated in a persistent state of high reactivity.

A
  • Glial cells mobilize and release calcium, glutamate and pro-inflammatory molecules
  • Magnesium blockade of the NMDA receptor is released and second messenger systems enabled
  • The LC becomes hyperactive, and initiates stress-related activation of other brain regions
  • Subjects can begin to report the perception of pain in the absence of tissue injury