Flashcards in central pain Deck (31):
what is the role of the central trigeminal pathway in central pain?
-representation of pain
- pain processing
- referred pain
how many layers are there in the medullary dorsal horn? what layers do Nociceptive specific fibers terminate on?
medullary dorsal horn- 10 layers
Nociceptive specific terminate mostly in superficial layers I and 2
Non-nocioceptive fibers terminate on what layers of the medullary dorsal horn?
terminate mostly in deeper layers III, IV,V
T/F: nociceptive and non-nociceptive terminate in separate/distinct layers of the medullary dorsal horn
False- Overlap in layers II & V
what 2 types of neurons are found in the medullary dorsal horn?
-Nociceptive specific neurons
-Wide dynamic range neurons
In the MDH, there can be Convergence of peripheral afferents with different __________
Referred pain partially explained by ___________ in MDH
what causes referred pain?
Pain & non-pain afferents converge on “pain-signaling” neuron
what occurs during central sensitization?
a low-threshold mechanoreceptor that usually signals for touch will signal for pain---- Allodynia
a low-threshold mechanoreceptor will work in conjunction with a nocioceptor to lower the threshold for pain reception- hyperalgesia
what are the steps to create central sensitization through C fiber activity?
A) C-fiber afferent barrage
B) MDH neuron response
C) Previously ineffective A-fiber now effective
What changes in the MDH neurons during central sensitization?
Depolarization by Substance P (tachykinin)
Modification of NMDA receptor ( structural change to remove Mg++ block)
Increase in conductance of NMDA receptor
what are the effects of A-fibers causing activation of the MDH pain centers?
A) A-fibers have a larger receptive field
B) A response to normally innocuous stimuli induces pain: A-beta fibers
Following pulpitis (inflammation of the tooth pulp), Inflamed teeth are “sensitizing” central neurons with input from the healthy __________ to make them more sensitive
(end result: contralateral/healthy teeth are more sensitive)
T/F: Trigeminal Tractotomy leads to the loss of sensation to the tooth pulp
Pulpal pain intact
what are the effects of a central lesion to the pons? (in the oral cavity)
Intraoral touch, thermal sensitivity and pain are all diminished
Following a Trigeminal Tractotomy, the ____________ and ________ still shows pain sensation
A lesion to the ______________ will Diminish intraoral and perioral pain
Pons (subnucleus oralis)
what is the response in Ventral Posterior Medial Thalamus to a noxious stimuli?
1. small receptive field
2. tracks the onset/offset of stimulus
3. stimulus - response linear
what type of pain response is seen in the n. Submedius?
1. large receptive field
2. response outlasts stimulus
3. neural representation of negative emotion: outlasts stimulus.
A MRI will visualize ____ tissue, while a PET scan will show ______ active tissue
MRI: visualize soft tissue
PET: metabolically active tissue
what is the role of the N. submedius & cingulate cortex in the processing of pain?
emotional component of pain
neural response outlasts stimulus (poor localization)
activity associated with anxiety
what is the role of the Thalamus (VPL) and somatosensory cortex in the central processing of pain?
localization of pain
neural response track pain stimulus
small receptive fields
how do Forebrain pathways modulate pain perception?
Anxiety can increase pain perception
The placebo effect suppresses pain perception
how is High anxiety induced when testing for it's effects on pain perception?
High anxiety induced by not knowing If Low or High pain stimulus coming
there is an increased activity in the __________________ Following Induction of Anxiety
Anterior Cingulate Cortex
what 3 regions of the CNS can modulate pain (in the descending pain pathway)
1.forebrain: ACC: anterior cingulate cortex
2. midbrain: PAG” periaquaductal (central) grey
3. rostral ventromedial medulla
Many of the descending pain control sites contain ___________ to suppress pain
descending pathways from the medulla contain both _______ and ________ fibers
(in regards to the pain control pathways)
Inhibitory and excitatory
presynaptic inhibition of pain is caused by what 2 sources?
medullary or local *enkephalin* input
(endogenous opoid input locally or from the medulla)
how could the reorganization of afferent fibers explain mechanical allodynia?
Loss of c-fibers following nerve injury,
e.g. postherpetic neuralgia
Sprouting of non-injured A-beta fibers into superficial layers (where nocioceptive C-fibers use to terminate)