Lecture 17 acute pain Flashcards

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1
Q

Define pain

A

Unpleasant sensory and emotional experience associated with actual or potential tissue damage.
Lots of types/descriptions: aching, burning, throbbing, electric shock like, dull, sore, nagging, piercing etc.
Associated with crying, sympathetic activation, behavioural changes.

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2
Q

Describe the receptors and pathways through which pain signals reach the brain.

A

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3
Q

How drugs/other factors can modulate the experience of pain.

A

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4
Q

Describe the similarities between physical and emotional/social pain.

A

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5
Q

Gate theory of pain

A

There is feedback loop in the spinal cord that determines which stimuli reach the brain.
Chronic stress opens gate
Adrenaline closes gate
Explains how pain can be ignored on battlefield but intensified when upset.
Rubbing sore limb/TENS may “close gate”.

Consult the slides for a graph

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6
Q

Describe the reciptors for pain

A

Nociceptors
sensory receptor capable of transducing noxious stimuli.
Free nerve endings
Several classes which respond to different stimuli
Stimuli
Mechanical
Temperature (extreme)
Electrical
Chemical (Capsaicin: Respond to heat/chilli/jalepenos)

Inflammation (mechanical and ↑nociceptor sensitivity)

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7
Q

Describe pain nerves

A

Aδ fibres: some myelin, faster for sharp pain.
C fibres: no myelin, slower, dull aching pain.
Synapse in the substantia gelatinosa in the dorsal horn of the spinal cord and use glutamate (and substance P).

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8
Q

Two sense pathways

A

Proprioceptors + mechanoreceptors - dorsal column at spinal cord - cross over at medulla - thalamus - primary somatosensory cortex

nociceptors + thermoreceptors - cross over at spinal cord - medulla - thalamus - primary somatosensory cortex

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9
Q

Ascending pain pathways

A

C & A fibre - cross over at spinal cord - medulla - midbrain - thalamus - insular, somatosensory cortex, anterior cingulate cortex

Primary somatosensory cortex.
Anterior cingulate – emotional aspects, sympathetic pain and social rejection.
Insular – modulate physical pain response.

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10
Q

Descending pain pathways

A

amygdala - PAG

hypothalamus - cross over at spinal cord

Amygdala (involved in emotions) and hypothalamus can modify pain responses by activating the periaqueductal gray (PAG).
PAG uses endorphins (“endogenous morphine”).

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11
Q

What happens when you have prolonged pain

A

Once pain alerts you to danger/potential danger continued pain is unnecessary.
Brain diminishes prolonged pain through endorphin release, which bind to opiate receptors in periaqueductal gray area.
Inescapable pain, exercise and sex all result in increased endorphin release and reduce pain sensitivity.

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12
Q

Drug treatments for pain

A

Opiates
Block the release of substance P in the periaqueductal gray.
Same mechanism as endogenous endorphins.

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13
Q

Mechanism of panadol and tylenol

A

Panadol (paracetamol)/Tylenol (acetaminophen)
Exact mechanism of analgesia unknown. (sounds like good science to me)
Both inhibit the synthesis of prostaglandins (pro inflammatory).
Analgesia is presumed central and related to reduced serotonin, opioids or through the endogenous cannabinoid system as blocking these systems reduce the analgesic effect.

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14
Q

placebo and acupuncture

A

Placebo
Placebo’s quite effective for pain.
Reduce the emotional aspects of pain via reducing activity in the cingulate (not somatosensory) cortex.
Also result in increased release of endorphins (placebo effect reduced with naloxone).
Acupuncture
Also results in release of endogenous opioids.

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15
Q

does social exclusion hurt

A

virtual ball toss game, same area as if physically hurting

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16
Q

do social exclusion, heartbreak hurt

A

virtual ball toss game, same area as if physically hurting

Recount a recent unwanted breakup while viewing a picture of their ex versus a painful heat stimulus.
Same brain regions activated in both conditions (anterior cingulate, insula and somatosensory cortex)
Similar findings in recently bereaved individuals.

17
Q

Tylenol for social pain?

A

Double blind randomised trial of tylenol vs placebo for 3 weeks.
Each night they rated “hurt feelings”
Tylenol participants had reduced daily hurt feelings over time whereas placebo didn’t change.
Also did same fMRI study with virtual ball toss game after 3 weeks Tylenol or placebo – results on next slide.

i am not sure as to how to interpret the results of the fMRI, please revisit the lecture

18
Q

Love and pain

A

25 women in stable relationships rated painful stimuli in 7 conditions:
Viewing a photo of their partner/stranger/ball
While holding partners hand/strangers hand/ball (behind screen)
Looking at cross hairs (control)

looking at photographs of their partner was even more effective than holding their hands

19
Q

Hypnosis and pain response

A

Numerous studies have shown hypnosis alters activity in the anterior cingulate cortex, amygdala, thalamus, insula and somatosensory cortex

Arms in ice water with or without hypnosis to reduce the unpleasantness.
Rated it just as intense but less unpleasant.
Reverse experiment done to reduce intensity.

what is reverse???

20
Q

therapeutic approahces to treating pain??

A

Love, medication and CBT??? see the second last slide