Pain Flashcards
What are nociceptors and how are they adapted to be easily stimulated?
Pain receptors - not stimulated all the time due to high threshold. however, they are sensitised by different mediators (e.g. prostaglandins, NorA, NO, ROS) so that they are easily activated
List neurotransmitters of nociceptors
Bradykinin K+ HT H+ ATP HIstamine
describe the difference in the two nociceptors
A-delta - faster and mainly detect mechanical (some heat)
C fibre axons - slower and polymodal - mechano, heat and chemical
Describe the difference in thermal receptors
C fibre axons - sense heat and only stimulated when in pain
A-delta - sense cold
describe the fast activated pain pathway
Physiological tramission through A delta fibres and regulated by thermo/mechanoreceptors. Short-lived and sharp, resulting in reflex - not affected by morphine
Describe the slo activated pain pathway
Pathophysiological trasnmission through C fibres. Stimulated by polymodal receptors resulting in spasm and guarding
Which pathway can morphine treat against?
Slow activated
What controls cognitive pain reception (emotions, mood etc)?
Anterior insula
Anterior cingulate gyrus
Prefrontal cortex
Explain the gate control theory
- Pain sends signals to dorsal horn of spinal cord via C fibres
- Rubbing the affected area stimulates tactile touch and therefore action potentials of A-beta fibres to spinal cord
- A-beta fibres split in the spinal cord, stimulating inhibitory neurons
- These inhibit the transmission of pain, reducing the feeling
way in which tens machines work
How do opiates work as analgesics?
Opiod receptors send action potentials to Descending Nociceptor Inhibitory Centre (DNIC) which releases mediators (e.g. 5HT and noradrenaline) downwars. These inhibit the UPWARD flow of pain
How do antidepressants reduce pain?
Antidepressants cause the mediators send out by DNIC to stay about for longer, prolonging their pain relieving effect
Where is the localisation of pain recognised?
Somatosensory cortex - made up of THALAMUS, S1&2 and Posterior Insula
What is the difference between smoatic and visceral nociceptive pain?
Somatic (skin, muscle and bones) - localised, showing dermatomal radiation and characterised as sharp, aching and gnawing
Visceral (internal organs) - vague distribution, presents as dull, dragging and cramps
How might neuropathic pain present?
shooting
burning
tingling
numbness
Why might NSAIDs be used over Paracetemol?
NSAIDs better for dental pain
