L17 - Acute Pain Flashcards
What is pain?
Unpleasant sensory and emotional experience associated with actual or potential tissue damage.
- highly modulated by emotions and cognition
- lots of types of pain
- associated with crying, sympathetic activation, behavioural changes.
Why is pain useful?
- Directs attention towards danger and HOLDS attention.
- ## Patients with congenital analgesia, who can’t feel pain,, have reduced life span - can bite off tongue etc. do more dangerous things.
What are factors that influence pain?
- Genetics
- age - older = more pain
- Sex - women = more pain
- Hair colour - red heads have higher sensitivity to thermal pain, but less sensitivity to chemical and electrical pain. NEED MORE ANAESTHETIC
What are factors that influence pain and can be modifiable?
- Context - situation influences pain - handle more pain during sport than at uni
- Prior life stressors/events - interventions…. surgeries
- Obesity - also more likely to be in painful situations, such as arthritis
- Anxiety/depression
- Attention - decrease pain when distracted
- Sleep
What is the gate theory of pain?
That there is a feedback loop in the spinal cord which determines which stimuli reaches the brain.
- Chronic stress opens the gate
- Adrenaline closes the gate
explains how pain can be ignored on battlefield, but intensified when upset.
rubbing sore limbs may close the gate.
gate is an inhibitory neuron. receives inputs from distractive stimulus (+) and noxious stimulus (-)
What are some examples of nociceptors?
- sensory receptors - capable of transducing noxious stimuli
- free nerve endings
- several classes which respond to specific stimuli
What are pain nerves?
A delta fibres - some myelin, faster for sharp pain
C fibres - no myelin, slower, dull aching pain.
comes into the spinal cord through dorsal horn and uses glutamate and substance P
mild pain - only glutamate
What is special about pain signals?
They get to the brain faster than ‘tough’ signals, although sometimes unmyelinated.
Bc largely only 2 synapses! transmission is slower across synapses.
What are the two sense pathways?
- Dorsal column-medial lemniscal pathway - TOUCH
2. spinothalamic tract - PAIN
Describe the spinothalamic tract/ascending pain pathway
FOR PAIN
nociceptor/thermoreceptor –> dorsal horn (crosses over in spinal cord –> contralateral spinal cord –> thalamus –> primary SSC (tells where the pain is), anterior cingulate (emotional response to pain), insular (moderates physical response to pain)
touch and pain signals go up opposite sides of spinal cord
Describe the Dorsal column-medial lemniscal pathway
FOR TOUCH
afferent nerve –> dorsal horn of sc –> medulla, crosses over –> thamalus –> primary SC
touch and pain signals go up opposite sides of spinal cord
What is the anterior cingulate’s role in pain?
emotional response to pain
- social rejection, sympathetic pain when you see others in pain
lesion –> not bothered by the pain really
What is the insular’s role in pain?
physical response to pain
lesions – altered sensitivity to pain.
if you stimulate it, gives pain in a specific region of body.
Describe the descending pathway for pain?
Pathways from amygdala and hypothealamus go down to the sc dorsal horn. Also involves the Periaqueductal Grey, which uses endorphins to inhibit pain..
this pathway regulates how much NT is released in the SC, can inhibit pain pathway.
eg. dude who cut off his arm
Prolonged pain?
Once pain alerts danger, continued pain is unnecesary.
Brain diminishes prolonged pain through endorphin release, binding to opiate receptors in periqueductal gray area.
Drug treatments for brain?
OPIATES - blocks the release of substance P in the preiaqueductal gray. Same mechanism as endorphins
Paracetamol & Tylenol - exact mech of analgesia unknown, but both inhibit the synth of prostaglandins which are pro inflammatory –> reduce inflammation.
Placebo - effective, reduces emotional aspects of pain via reducting activity in cingulate cortex. also increases endorphins
Acupuncture - also results in release of endogenous opioids.
Marijuana - cannabinoids act at periphery
Capsaicin cream/patches - releases substance P to create slight burning pain but depletes the cells of substance P which slowly synthesises… reduction in pain
What systems do we think analgesia works through?
Due to reduces serotonin, opiods or endogenous cannabinoid systems, as blocking these systems with naloxone reduces the analgesic effect
Does social exclusion hurt?
- virtual ball toss game b/w 2 computers and 1 real participant
- initially the computer throws to everyone equally but then excludes the real participant
- brain regions involved in physical pain and social exclusion were very similar
- people who had strong friendships were less affected than those who were socially anxious
Heartbreak and pain?
- recounting a recent break up while viewing ex’s picture, VS. painful heat stimuli
- same brain regions activated in both conditions - anterior cingulate, insula and SSC.
similar findings in recently bereaved patients.
Tylenol for social pain
found tylenol reduced daily hurt feelings over time, when placebo didn’t change.
- anterior cingulate and insular lit up more for placebo group when excluded in ball toss game
How can love affect pain?
Less pain was felt when holding partner’s hand .
more pain when holding stranger’s hand
Viewing a photograph of partner decreased pain double holding their hand.
Meditation and pain?
- studies show pain is reduced following meditation
- reduced pain related to activation of SSC and INSULA
- INCREASE activation of anterior cingulate
- reduced amygdala activation and negative emotions in response to pain
mindfulness effects weren’t reduced by naloxone, so it’s not working through endorphins.
Hyponosis and pain response?
- Hypnosis alters activity in anterior cingulate, amygdala, thalamus, insula and SSC.
- arms in ice water with hypnosis - people found it just as intense, but less unpleasant.
