L25 Pain Flashcards
what are the 2 types of pain
nociceptive pain
neuropathic pain
what are the 2 types of pain
nociceptive pain
neuropathic pain
define nociceptive pain
direct stimuli of nociceptors and have the potential to cause tissue damage
define neuropathic pain
CANNOT be explained by a simple activation of nociceptors by tissue damage
includes pain where the mechanism is a site of atypical somatosensory processing the PNS or CNS
define first pain
- sharp and quick pain resulting form the activation of mechanical or thermal receptors
- receptors use A delta fibers = myelinated and very fast
- this is known as the “ouch effect”
define second pain
- much slower onset pain, more like a burning sensation resulting from polymodal nociceptors
- these receptors use unmyelinated C fibers that have a much slower velocity this a slower onset
does the brain have nociceptors?
no
how do headaches arise?
irritation of neighboring tissue, most often the meninges
describe visceral pain
visceral organs have nociceptors
results from the stimulation of visceral and deep somatic nociceptors - conduct signal via unmyelinated C fibers
describe referred pain
visceral nociceptive activation is perceived as a cutaneous painful sensation
how can referred pain be explained?
neurons in the dorsal gray matter of the spinal cord receive convergent input from both somatic and visceral afferents at the same location and are projected into the ALS
in the event of tissue damage, what chemical are released that can activate chemical nociceptors?
- bradykinin - from blood
- histamine - from mast cells
- potassium - from damage cells (remember increase extracellular K+ depolarized membrane potential)
define hyperalgesia
enhanced sensitivity and responsivity to an area around damaged tissue
what causes hyperalgesia
increasing nociceptor sensitivity cause by chemicals released at site of trauma
- prostaglandins and leukotrienes from damaged cells
- substance P from primary afferent pain fibers
define second pain
- much slower onset pain, more like a burning sensation resulting from polymodal nociceptors
- these receptors use unmyelinated C fibers that have a much slower velocity this a slower onset
does the brain have nociceptors?
no
how do headaches arise?
irritation of neighboring tissue, most often the meninges
describe visceral pain
visceral organs have nociceptors
results from the stimulation of visceral and deep somatic nociceptors - conduct signal via unmyelinated C fibers
describe referred pain
visceral nociceptive activation is perceived as a cutaneous painful sensation
how can referred pain be explained?
neurons in the dorsal gray matter of the spinal cord receive convergent input from both somatic and visceral afferents at the same location and are projected into the ALS
define hyperalgesia
enhanced sensitivity and responsivity to an area around damaged tissue
what causes hyperalgesia
increasing nociceptor sensitivity cause by chemicals released at site of trauma
- prostaglandins and leukotrienes from damaged cells
- substance P from primary afferent pain fibers
explain gate control in the spinal cord
if a touch fiber is stimulated, it will meet the pain fiber in the dorsal horn (similar to referred pain) and will activate interneurons that will inhibit the synapse between the first and second order pain fibers
what does the stimulation of the touch fiber cause the interneuron to release?
enkephalin (endogenous opiod) = inhibits pain fibers
what is the mechanism of opiods (to AP duration, EPSP durations, polarization)
decrease AP duration
decrease EPSP duration
hyperpolarize the second order neuron
what is the role of serotonergic and noradrenergic fibers in modulating pain
they act the same as gate control pathway
they both synapse on the opiodergic interneuron where they control the transmission of the pain fibers
what is the MOA of aspirin
decrease COX resulting in decrease of prostaglandins (which normally sensitize sensory afferent fibers)
what is a dorsal rhizotomy
in extreme cases (terminal cancer etc) DRG is removed to stop pain transmission
is acupuncture beneficial to pain relief
its a bunch of crap - it may release opiod peptides that could decrease pain fiber transmission, but there are serious adverse effects that are BAD
