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Mechanisms of Pain Modulation
Mechanisms of Pain Modulation
100
Anatomy
Graduate
02/24/2015

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Term
an unpleasent but adaptive experience that signals the body to protect itself from tissue damage
Definition
pain
Term
occurs when tissues are being damagedm causes individuals to remove the stimulus or slow down, sleep etc to allow tissues to heal
Definition
pain
Term
a protective mechanism of the body
Definition
pain
Term
pain is not the same as what?
Definition
nociception
Term
emotional, affective, and arousal aspects of such stimulation
Definition
pain
Term
detection and localization of a stimulated pain receptor
Definition
nociception
Term
sensory process that provides signals that trigger pain
Definition
nociception
Term
while nociceptors may fire wildly and continually, what will happen to pain
Definition
pain may come and go
Term
more than any other system, which qualities of nociception can be controlled from within the brain itself?
Definition
cognitive
Term
what type of pain is generally not felt in the deeper tissues of the body
Definition
fast acute pain
Term
fast acute pain can be classified as being what (2)
Definition
nociceptive or neuropathic/neurogenic
Term
nociceptive fast acute pain is due to what
Definition
activation of peripheral nociceptors in skin/soft tissue in response to tissue injury and inflammation
Term
neuropathic/neurogenic fact acute pain is a result of what more commonly
Definition
injury/inflammation of peripheral nerves
Term
neuropathic/neurogenic fast acute pain is a result of what less commonly
Definition
pathological involvement of CNS neurons
Term
what are some PNS disorders that cause neuropathic fast acute pain? (4)
Definition
herpes zoster, diabetes, trigeminal neuralgia, trauma (CRPS)
Term
what type of fast acute pain is not responsive to Na+ channel blockers?
Definition
nociceptive
Term
what type of fast pain is responsive to Na+ channel blockers
Definition
neuropathic
Term
Which fast pain is dependent on the presence of Na+ channels and Action potential conduction?
Definition
neuropathic
Term
Which fast pain is not dependent on the presence of Na+ channels and Action potential conduction?
Definition
nociceptive
Term
What are examples of Sodium channel blockers
Definition
lidocain, gabapentin
Term
slow (chronic) pain examples: (5)
Definition
burning, itching, throbbing, nauseous, chronic pain
Term
associated with tissue destruction in skin, or deep tissues of the body
Definition
slow (chronic) pain
Term
pain that is felt or perceived to be in one region of the body but is actually the result of damage to a deeper organ, usually in the same dermatome
Definition
referred pain
Term
when does referred pain occur
Definition
vague, non-specific information from deeper organs is relayed to spinal cord laminae, as that info ascends the SC the brain interprets it coming from teh more defined limb
Term
pain felt by some individuals with amputations, perception of pain in the amputated limb, related to amount of pain in the limb prior to amputation, and to the number of neuromas in teh stump
Definition
phantom pain
Term
what are the 4 types of pain(nociceptors).
Definition
mechanical, thermal, chemically-sensitive, polymodal
Term
nociceptors that are activated by intense pressure applied to skin
Definition
mechanical nociceptors
Term
mechanical nociceptor characteristics (4)
Definition
thinly myelinated, small diamater, A-delta fibers, conduction velocity of 5-30 ms
Term
nocicpetors activated by extreme temperatures
Definition
thermal nociceptors
Term
thermal nociceptor characteristics (5)
Definition
small diamater, thinly myelinated, A-delta fibers, with conduction velocity of 5-30 m/sec
Term
chemically-sensitive nociceptors characteristics (3)
Definition
unmyelinated C fibers with conduction speeds .5-2m/sec
Term
polymodal nociceptors respond to what
Definition
intense mechanical, thermal, and chemical stimuli
Term
polymodal nociceptors chracteristics (3)
Definition
unmyelinated C fibrs with conduction speeds of .5-2m/sec
Term
all nociceptors represent what terminals of fibers?
Definition
peripheral
Term
sharp pain is mediated by what type of fibers?
Definition
a delta
Term
sharp pain comes form what nociceptors?
Definition
mechanical and thermal
Term
chronic pain is carried by what fibers?
Definition
unmyelinated slower conducting C fibers
Term
chronic pain is activated by what nociceptors?
Definition
chemical and polymodal
Term
refers to an innocuous stimulus mediated by A-beta fibers evokes the perception of pain
Definition
allodynia
Term
responsiviness of nocicpetors to painful stimuli such that the response is lessened or heightened
Definition
sensitization
Term
sensitization can occur where
Definition
in the CNS (drosal horn neurons) and PNS
Term
increased/exaggerated sensitivity (lower threshold) of pain receptors to noxious stimuli, reectpors fire more easily
Definition
hyperalgesia
Term
occurs within the area of damaged tissue, caused by peripheral sensitization
Definition
primary hyperalgesia
Term
occurs when the tissues surrounding the damaged tissue become supersenstive, caused by central sensitization
Definition
secondary hyperalgesia
Term
primary hyperalgesia is caused by what
Definition
peripheral sensitization
Term
primary hyperalgesia is caused by what
Definition
peripheral sensitization
Term
secondary hyperalgesia is caused by what
Definition
central sensitization
Term
periphereal sensitization is a result of direct release of chemical mediators into the inflamed area such as what
Definition
mast cells (histamine and serotonin) and prostaglandins (fibroblasts)
Term
peripheral sensitization: mast cells and prostanglandins released into the inflamed area act directly on what?
Definition
receptive membrane of nociceptores
Term
peripheral sensitization: what are other mediators that are released indirectly?
Definition
macrophages, substance P
Term
peripheral sensitization: what do the macrophages release
Definition
leukotrienes (interleukin-1)
Term
peripheral sensitization: macrophages release leukotrienes which signal what
Definition
fibroblasts to relase prostaglandins
Term
peripheral sensitization: where is substance P released from?
Definition
nociceptor terminals themselves
Term
peripheral sensitization: where is substance P synthesized?
Definition
cell bodies (Dorsal root ganglion, trigeminal ganglia) of primary C-fiber afferents
Term
peripheral sensitization: after synthesis of substance p in cell bodies of primary c-fiber afferents where is it transported?
Definition
centrally onto 2nd order dorsal horn neurons and peripherally onto the nociceptor
Term
peripheral sensitization: release of substance P contributes to primary hyperalgesia by causng what?
Definition
mast cells to degranulate and release histamine
Term
peripheral sensitization: how does the release of histamine from mast cells contribute to primary hyperalgesia?
Definition
decreases teh threshold for activation of nociceptors
Term
peripheral nerve damage results in what?
Definition
afferent pathway conducting pain to the CNS is compromised
Term
if the afferent pathway conducting pain to the CNS is compromised what would one expect?
Definition
pain to be depressed not augmented
Term
Peripheral nerve damage often results in many intractable pain states such as what (5)
Definition
diabetic neuropathy, causalgia, phantom limb pain, trigeminal neuralgia, CRPS
Term
after axotomy, or segmental demyelination, may afferent axons become what?
Definition
hyper excitable
Term
after axotomy, or segmental demyelination, many afferent axons become hyper excitable and do what?
Definition
generate an ongoing spontaneous discharge that originates from the site of injury
Term
after axotomy, or segmental demyelination, many afferent axons become hyper excitable and generate an ongoing spontaneous discharge that originates from the site of injury. What is this discharge called?
Definition
ectopic dishcharge
Term
discharge which originates from the site of injury not from the initial segment of the axon
Definition
ectopic discharge
Term
in those with peripheral neuropathies, there is a directly correlation between complaints of pain and paresthesia and what
Definition
ectopic discharge
Term
an accumulation of voltage-regulated/gated Na+ channels in the injured region due to a remodeling of the neuronal membrane results in what
Definition
ectopic discharge
Term
the amount of stimulus necessary for one to experience pain
Definition
threshold
Term
the amount of pain one can withstand
Definition
tolerance
Term
gate theory example
Definition
rubbing arm after getting it pinched
Term
A-fiber input reaches SC first and turns on inhibitory interneurons. This inhibition then turns off/decreaces teh ascending pain input
Definition
gate theory
Term
what is required for the gate theory to continue working?
Definition
continued activation of the A-beta fibers, once the activation stops, pain returns
Term
the gate theory can have a short duration, what mechanism has longer-acting gating?
Definition
supraspinal gating
Term
pain modulation occurs via a system in which direction?
Definition
descending
Term
pain modulation descending system: Origin
Definition
cerebral cortex and hypothalamus
Term
pain modulation descending system terminates where
Definition
neurons in the periaqueductal gray
Term
pain modulation: cortical input originates from what lobes?
Definition
frontal and insular
Term
pain modulation: frontal lobe is responsible for what
Definition
cognitive activation of the pain modulating system
Term
pain modulation: insular lobe is responsible for what
Definition
modulates the autonomic response to pain that reciprocally influences the emotional response
Term
pain modulation: projections from the periaqueductal gray descend to what
Definition
raphe nuclei
Term
pain modulation: projections from the periaqueductal gray descend to raphe nuclei where?
Definition
in the medullary reticular formation
Term
pain modulation: from raphe nuclei, axons descend to synapse where
Definition
dorsal horn spinal cord neurons
Term
pain modulation: other brainstem centers project to spinal cord levels and inhibit nociceptive projections neurons in the dorsal horn both directly and indirectly. Where are these brainstem centers lcoated?
Definition
pons and medulla (eg locus coeruleus)
Term
pain modulation: other brain stem centers on the pons and medulla project into the SC level and inhbit nociceptive projection neurons in the dorsal horn directly and indirectly through interneurons in what
Definition
substantia gelatinosa
Term
pain modulation: which tract contains receptors for endogeneous opiate neurotransmitters ie endorphis
Definition
paleo-spinothalamic tract
Term
what is the role of endogenous opiods?
Definition
modulate our response to pain
Term
how do endogenous opioids modulate our response to pain?
Definition
extent to which pain is percieved, one's emotinal response including affecting and motivational components
Term
how is the pain-modulating system activated?
Definition
noxious stimulation can activate the system
Term
noxious stimulation can activate the pain modulation system via what tracts?
Definition
paleospinothalamic tract
Term
noxious stimulation can activate the pain modulation system via tracts of the Paleospinaothalamic tract to what structure?
Definition
brain stem structures
Term
what is the importance of the brainstem structures which the tracts of the paleo spinothalamic tract connect to?
Definition
whose neurons represent the source of the descending modulating network
Term
what can depress the modulating system?
Definition
anxiety
Term
what happens when the modulating system is depressed?
Definition
exacerbation of pain
Term
what is a conditioned reaction to pain modulation?
Definition
an expectation of relief as in the placebo effect from a prior experience
Term
opiods reduce pain and produce what
Definition
analgesia
Term
opiods as exeogenous drugs bind with opium receptors where
Definition
in teh periaqueductal gray and other areas
Term
oral administration of exogenous opiods effects the entire body and can have negative side effects, so where would these drugs be administered to reduce these side effects
Definition
spinal crd
Term
spinal blocks admininstered to the spinal cord are place where?
Definition
subdural space (intrathecally) or superficial to the dura mater (epidurally)
Term
which is the least successful pain modulation technique
Definition
surgical intervention
Term
example of a peripheral surgical attempt to control pain
Definition
dorsal rhizotomy
Term
example of a central surgical procedure to control oaun
Definition
frontal lobotomies
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