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21 Cards in this Set
- Front
- Back
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what are some examples of subst released in response to tissue damage?
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ATP, bradykinin, 5HT (serotonin), prostaglandins
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what is the main stimulus for pain?
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tissue injury; activates free nerve endings
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what is the most important synapse in the detection and modification of pain?
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1st synpase b/w AD(elta)/ C fiber central afferents and the dorsal horn projection neuron (DHPN)
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what activates the DHPN?
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substance P rel by A(Delta)/ C fibers
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what is the ATP receptor on the free nerve ending?
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P2X
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3 categories of pain
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physiologic (normal)
inflammatory (pain) neuropathic pain |
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what is neurogenic inflammation?
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a process by which nociceptor neurons aplify and extend the inflammatory process
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what are conditions under which pain is perceived? what can cause pain?
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nociceptor activity can cause pain
you can have activation of nociceptors w/o the perception of pain you can have pain w/o the activation of nociceptors |
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what is allodynia?
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when a formerly non-painful stimulus (below pain threshold) is perceived as pain
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what is hyperalgesia?
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when stimuli that were normally perceived as painful are now perceived as MORE painful
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what causes hyperalgesia?
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sensitization of nociceptor endings-> incr in reactivity to a stimulus
often due to local inflamm which lowers the threshold of the nociceptor |
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what are 3 types of nociceptors?
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mechanical nociceptors: localized, rapid onset (ex: sharp obj)
thermal nociceptors: heat above 45C (heat pain) polymodal nociceptors: resp to several stimuli; mediated by C fibers; delayed, poorly localized; dull aching pain |
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what are some ex of receptors on the free nerve ending?
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TRPVs
P2X (binds ATP) TrkA (binds NGF) |
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what are TRP channels?
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family of receptors on free nerve endings
TRPV1- AD(elta) and C fibers; detects moderate heat (45C) and Capsaicin (chilis) TRPV2- higher temps (52); AD(elta) fibers only |
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what is the process that leads to allodynia? why do mechanoreceptors lead to the perception of pain?
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A(Beta), A(Delta), and C fibers all terminate on DHPN
however, normally, DHPN has no R for NT rel by A(Beta). w/ inflamm, R for mechanoR form and so the DHNP becomes sensitized to all kinds of stimuli |
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what is the mxn of hyperalgesia?
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lower threshold/sensitization- upregulate expression of R on free n. ending (ex: P2X)-> incr firing rate of DHPN
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explain referred pain in a MI
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nociceptors in heart and L arm both synapse on same DHPN
DHNP is used to being stimulated by free n. ending from L arm so when nociceptors from heart activate the DHPN, the signal is misinterpreted as coming from the L arm |
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what is the descending control of pain perception?
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mediated by ALS fibers (spinomesencephalic) that synapse at periaqueducal gray; stimulates descending inputs that synapse in nucleus raphe magnus and rel serotonin on serotonergic neurons; synapse on inhibitory enkephalinergic interneurons that rel enkephalin on C fiber terminals, preventing NT rel from pain fiber into DHPN
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what are enkephalinergic nerurons?
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inhibitory interneurons; rel enkephalin to prevent transmission of pain from C fibers to DHPN
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what is the gate theory of pain? what does it explain?
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explains why we rub areas that hurt
transmission of ascending pain info is blocked by concurrent stimulation of A(Beta)s |
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mxn of gate theory of pain
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when bump your knee, C fibers rel glutamate onto DHPNs causing them to fire and transmit pain
by rubbing your knee, you activate mechanoR A(Beta) fibers which activate INHIBITORY neurons that synapse and prevent activation/firing of DHPN |
