Pain and pain supression Flashcards
(57 cards)
how do nociceptors work
damaged skin or organs
release prostaglandins made as inflammation response
sensitise free nerve endings so more likely to fire action potentials
axons in adelta fibres
highly myelinated
function of adelta fibres
convey mechanical pain very quickly and precisely (early pain)
informative about location
axons in c fibres
unmyelinated axons
c fibres functions
convey pain more slowly and less precisely (late pain)
Vague about location
what type of stimuli are c fibres sensitive to
extremes of mechanical stimulation
pungent irritants
temperature, acid and capsaicin
why is pain perception a dual brain mechanism
Pain sensation (physical) - primary SS cortex
Immediate unpleasantness perception - anterior cingulate cortex
how do stressful situations supress pain
stress activates the DAG (descending analglesia circuit)
NOT adrenaline - although happens simultaneously
what is the placebo effect
telling an individual that they have been given a drug and it having an effect on pain experienced
how may acupuncture be used to treat pain
triggers the activation of the DAC - can also be stimulated with currents using direct placement of electrodes
how has the placebo effect been investigated
skin cream given told reduces pain
lead to activation of the dorsolateral prefrontal cortex
this activates the PAG (peri-aqueductal grey matter) which activates the DAC
how is capsaicin used to treat pain
Used topically on the skin for muscle pain
how does capsaicin work as pain relief
Triggers a response in C fibres (overstimulates) - results in substance P release - depletes amounts in sensory neuron terminals, resulting in local analgesia
how is the descending analgesia circuit involved in pain perception
Opiates inhibit activity from inhibitory neurons in PAG - increases activity of axons descending to raphe nucleus
excites neurons in raphe nucleus whose axons descend in the dorsal columns of the spinal cord
activity excites spinal interneurons that block incoming pain signals
describe neurotransmitters involved in disinhibition in DAC
GABA binds to projection neurons - results in hyperpolarisation - less likely to fire
Endogenous opioids - hyperpolarise the membrane of interneurons - GABA no longer released at the synapse between inter/projection neurons
what are NSAIDs
non-steroidal anti-inflammatory drugs
examples of NSAID’s
Aspirin
ibuprofen
why do NSAIDs act peripherally
poor blood-brain-barrier penetration because of binding proteins in the blood
mechanism of action of NSAIDs
Inhibition of cyclo-oxygenase 1 and 2 (COX)
Results in the reduction of the production of prostaglandins - reduction in both inflammation and pain
side effects of NSAIDs
COX-1 involved in blood clotting: aspirin prevents blood clotting
COX-1 involved in protection of stomach lining from acid: NSAIDs bad for stomach
best understood mechanism of paracetamol
Reacts with endogenous molecules to form an agonist of TRPV1 and cannabinoid receptors
TRPV1 receptors found on nociceptors
CB-1 found in central and peripheral pain related circuit
what is an opiate
Natural alkaloids derived from the opium poppy plant
what is an opioid
Includes all substances that interact with opioid receptors in the brain
what are endorphins
Endogenous opioid system – reduce pain and stress and enhance feelings of well-being
