topic 5: pain and pain perception Flashcards
what is vitodilation?
bring blood to the site which is why you go red.
what are the 2 types of nociceptors?
myelinated and unmyelinated axons
myelinated axons
convey mechanical pain in a quick and percise way- early pain.
unmyelinated axons
pain more slowly and less precisely. Late pain: sensitive to various things including stimulation or irritants like acid.
define myelin
fatty sheets made by schwann cells and between the sheets are nodes of ranvier.
what is the dual brain mechanism behind pain perception
pain sensation is the pirmary SS cortex, immediate pleasantness perception- ACC
pain suppression- different methods
non drug approaches, capsaicin, NSAIDS, paracetamol, opiates and cannabis.
brief summary of the descending analgesia circuit
- opiates inihibit the inhibitory neurons in the PAG- increases neuronal activity in raphe nucleus.
- these neurons descend into dorsal columns of spinal cord.
- excite spinal interneurons that block incoming pain signals.
what are the non drug approaches to suppressing pain?
direct stimulation of PAG- measure reduction in pain using placebo- activates PAG and DAC.
capsaicin- role in pain suppression
used on skin for muscle pain, depletes sensory neuron terminals of substance P, local analgesia.
what are NSAIDs
non steroidal anti-flammatory drugs like aspirin. They act peripherally; poor blood brain barrier penetration because of binding proteins in the blood.
what is the mechanism of action behind NSAIDs
inhibition Cox 1 and Cox 2- reduces the production of prostaglandins. Side effects; blood clotting and bad for stomach.
what are the interactions of paracetamol?
reacts with endogenous molecules to form AM404, agonist of TRPV-1 and CB-1. TRPV1- found on nociceptors.
what are opiates?
derived from the opium poppy, long time use and very powerful analgesics.
opium
smoked or eaten, e.g. morphine- only 20% crosses blood-brain barrier. codeine (cough suppressant), heroin (injected), oxycodin (slow uptake- usually pills) .
what are the short term effects of opiates?
relieve pain, cough and diarrhoea, hypothermia and sleep.
psychological action behind opiates
mimic actions of endogenous opiods like endorphins- bind to receptors all over the body.
what are the 3 major sub types of opiod receptors
delta, kappa and mu- present in brain areas like preoptic or the PAG (pain relief and pleasure).
what makes opiates so addictive?
mestoencephalic dopamine system: VTA opiates inhibit GABA neurons which project to the NA which releases more dopamine. There is an independent effect but similar to dopamine from VTA.
cannabis
smoked or eated, more active compounds within the smoke, easily cross blood brain barrier. Half life of 7 days.
psychological action of cannabis
tetrahydrocannabinol is a partial agnoist on CB1 and CB2 receptors, responsible for psychedelic effects.
what are endo cannabinoids?
endogenous ligand of cannabinoid receptors are anandamide and 2-AG- receptors in hippocampus. suppress the release of NTs.
