Pain Flashcards
Causes of loss of pain
nerve damage, loss of fingers, diabetes
Describe pain
discriminative sensation, graded motivation
What are the two theories for pain
specificity, convergence
Describe the specificity theory
pain is distinct - specific receptors
describe convergence theory
pain is integrated - convergent activity, distributed network
Describe nociceptors
afferent, free nerve endings
How are nociceptors classified
according to stimulus, fibre type and conduction velocity
What are the two fibre types in nociceptors
lightly myelinated a-delta, un-myelinated c fibres
Characteristics of a-delta fibres
fast, mechano sensitive, mechano thermal sensitive
What do C fibres detect
mechanical, thermal, chemical
Which fibre is slowest
C fibres
How can fast pain be mimicked
direct stimulation of a-delta fibres
How can slow pain be mimicked
stimulation of C fibres
Where is the capsaicin receptor active
nociceptive a-delta and c fibres at 45C
What do the capsaicin receptors respond to
heat
What does capsaicin mimic
endogenous vanilloids released by stress tissues
What are the two central pain pathways
sensory discriminative, affective motivationl
describe the sensory discriminative pathway
signals intensity, location of stimulus
What does the affective motivational pathway signal
unpleasantness
What tract does the discriminative pain pathway involve
spinothalamic tract - anterolateral system
Measurement of what activity correlates to the intensity of pain
somatosensory cortex activity
What regions elicit an emotional response to pain
insult and cingulate cortex
What is hyperalgesia?
increased response to a painful stimulus
Example of hyperalgesia
hypersensitive damaged skin
What is Allodynia?
painful response to normal stimuli
Example of allodynia
painful sensitivity of sunburnt skin
What is the function of bradykinin
affects function of nociceptive molecular receptors
What is the effect of prostaglandins
lower threshold for axon potential generation
What is COX important for?
prostaglandin synthesis
Which painkillers act on COX
aspirin, ibuprofen
Where are prostaglandins released
dorsal horn
What causes hyperpathia
fibre or axonal loss
what is hyperpathia
detection threshold for pain is raised
What is the result of hyperpathia
extreme pain in response to normal stimulus
What diseases are associated with hyperpathia
shingles, diabetes, MS
What does phantom limb pain indicate
bodies central representation isnt passive
What do mechanoreceptors inhibit
nociceptive C fibres - spinal cord
What do enkephalins inhibit
pain fibres
What are enkephalins
endogenous opioid family peptides
Which phenomena do not fit with specificity theory of pain
phantom limb, placebo effect, referred pain
