W5_07 Pain (Ballyk) Flashcards
define noxious
causing tissue damage
define dysesthesia
abnormal unpleasant sensation
define hyperalgesia
increased sensitivity to pain
define allodynia
pain sensation elicited by a normally non painful stimulus
difference between nociceptive pain and neuropathic pain?
nociceptive is normal pain (tissue damage or inflammation);
neuropathic pain is an issue with the reporting system
what are the three types of nociceptors?
thermal;
mechanical;
polymodal
thermal nociceptors are which kind of neuron fibre?
A delta
mechanical nocicceptors are which kind of neuron fibre?
A delta
polymodal nociceptors are which kind of neuron fibre?
C
what are the differences between A delta and C fibres?
A delta: fast pain, localizable
C: slow pain, diffuse, evoke emotions
what kinds of fibres encode touch?
A beta (to DC/ML)
which two mechanisms cause inflammation?
axon reflex;
tissue damage
which two molecules are released by nerve fibre collaterals to cause inflammation?
CGRP;
Substance P
axon collaterals target which three structures to cause inflammation?
mast cells (histamine);
arterioles and capillaries (redness, heat, swelling);
platelets (serotonin or 5-HT release)
histamine does what to nociceptors?
activate
prostaglandin does what to nociceptors?
sensitize
bradykinin does what to nociceptors?
activate
potassium does what to nociceptors?
sensitize
leukotriene does what to nociceptors?
sensitize
serotoninn does what to nociceptors?
activate
difference between axon reflex and damaged cell “reflex” on nociceptors?
axon reflex causes activation and cell reflex causes sensitization
difference between 1º and 2º hyperalgesia?
1º = region of skin that is damaged; 2º = region of skin around damaged skin
how do NSAIDs work?
block cyclo-oxygenase (COX);
thus decrease PGE;
thus decrease sensitization;
thus less pain
naproxen and indomethacin are examples of what class of drugs?
NSAIDs
how does referred pain work?
afferents from the skin and the viscera synapse on the same 2º spinal neuron in the dorsal horn
how does touch inhibit pain?
while the A delta and C fibres are causing pain, A beta fibres activate interneurons that then inhibit activation of the 2º neuron in the dorsal horn.
what are enkephalins?
endogenous opiods released from dorsal horn interneurons
how do enkephalinergic interneurons inhibit pain?
these will prevent NT release in the 1º afferent nerve terminal and hyperpolarize the postsynaptic 2º neuron. they are activated by the descending periaqueductal grey neurons.
what’s the wiring that causes an emotional response to pain?
spinal lemniscus neurons also send collaterals to reticular nuclei of the thalamus. the 3º neurons connect to cingulate gyrus (limbic system)
diabetic neuropathy, trigeminal neuralgia, post-herpetic neuralgia, brachial plexus avulsion pain, spinal injury pain are examples of what kind of pain?
neuropathic pain (not nociceptive)
