Lecture 17 acute pain

Question 1

Define pain

Answer 1

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.

Question 2

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

Answer 2

See other cards

Question 3

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

Answer 3

See other cards

Question 4

Describe the similarities between physical and emotional/social pain.

Answer 4

See other cards

Question 5

Gate theory of pain

Answer 5

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

Question 6

Describe the reciptors for pain

Answer 6

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)

Question 7

Describe pain nerves

Answer 7

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).

Question 8

Two sense pathways

Answer 8

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

Question 9

Ascending pain pathways

Answer 9

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.

Question 10

Descending pain pathways

Answer 10

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”).

Question 11

What happens when you have prolonged pain

Answer 11

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.

Question 12

Drug treatments for pain

Answer 12

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

Question 13

Mechanism of panadol and tylenol

Answer 13

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.

Question 14

placebo and acupuncture

Answer 14

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.

Question 15

does social exclusion hurt

Answer 15

virtual ball toss game, same area as if physically hurting

Question 16

do social exclusion, heartbreak hurt

Answer 16

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.

Question 17

Tylenol for social pain?

Answer 17

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

Question 18

Love and pain

Answer 18

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

Question 19

Hypnosis and pain response

Answer 19

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???

Question 20

therapeutic approahces to treating pain??

Answer 20

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