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.
