EX1; Central Pain Flashcards
These nociceptors terminate mainly in the superficial laminae (I, II), although there is an important termination in layer V too; in the medullary dorsal horn (n. caudalis)
A-delta
c-polymodal
Non-nociceptive terminals are mainly where
in the deep laminae of the medullary dorsal horn
Following a peripheral nerve injury, there is postganglionic degeneration of what
c-fiber terminals in the superficial layers of the dorsal horn
Upon c-fiber degeneration in the dorsal horn after injury, what becomes of that A-fibers
the A-fibers in the deeper layers can sprout into the superficial layers, activating 2nd order pain signaling neurons in the superficial layer
What two types of neurons are found in the medially dorsal horn
nociceptive specific neurons
wide dynamic range neurons
This neuron represents convergence of a nociceptive neuron and a low-threshold A-beta type low threshold (non-nociceptive) type cell
wide-dynamic range neuron
Wide-dynamic range neurons may also have this, in which the center area is excitatory to pain and touch (wide-dynamic) but the surround is inhibitory to pain stimuli
“center surround” receptive-field organization
Activation of the center-surround receptive field may be involved with what
referred pain
Wide-dynamic range neurons in nucleus caudalis responds to what different type of stimuli
referred pain
innocuous and noxious stimuli
light touch and pressure to facial region
painful pinch and heat
electrical stimulation of TMJ and tooth pulp
True or False
the nucleus caudalis is the only part of the trigeminal complex that processes oral pain
False; it is not the only part
One frequent observation in trigeminal pain is that it is what
referred; pathology or insult to one area results in pain experienced somewhere else
Referred pain is partially explained by what in the MDH
convergence; pain and non-pain afferents converge on “pain-signaling” neurons
These fibers carry the pain message from the secondary hyperalgesia zones to the brain
A-beta fibers
How is it that the normal light touch sensation A-beta fibers carry pain signals to the brain
normal A-beta fibers release glutamate but is ineffective at the synapse because of Mg+ block in the NMDA receptor, intense pain via a C-fiber sensitizes (removes Mg block) the postsynaptic neuron to non-painful beta input
What three things involve MDH neuron response involving c-fiber activation of a-beta
depolarization by substance P
modification of NDMA receptor (remove Mg block)
increase conductance of NMDA receptor
respons to innocuous stimuli induces pain
What are the pain thresholds for healthy vs unhealthy teeth
high pain threshold for normal teeth
much lower pain threshold for inflamed teeth
lower pain threshold in contralateral healthy teeth; due to ipsilateral innervation
The inflamed teeth are “sensitizing” central neurons with what input
from healthy contralateral side to make them more sensitive
What other region in the has been shown to also be a “pain center” besides nucleus caudalis
nucleus oralis
True or False
Not all oral and facial pain is mediated by trigeminal fiber terminating in MDH
True
What two aspects of pain cannot be explained by brainstem mechanisms
perceptual and emotional components in the forebrain
Pain fibers terminate in midline thalamic nuclei including the nucleus submedius which projects to the cingulate cortex which then deals with which aspect of pain
emotional
Pain fibers rom the MDH cross and ascend in trigeminothalamic tract to terminate in the ventral posterior lateral nucleus (VPL) then to the somatosensory cortex which then deals with which aspect of pain
discrimination (localization); where is the pain, how intense is it, etc.
Other aspects of pain response including some reflex action is mediated by which part of the brainstem
reticular formation
What is specific about the neural response regarding the N. submedius and CC
neural response outlasts stimulus (poor localization)
also large receptive field
N. submedium and CC also deal with this
activity associated with anxiety
What is specific about the neural response regarding the VPL and somatosensory cortex
neural response track pain stimulus; onset and offset follow the stimulus closely
What is the receptive field like involving VPL and SS complex
small
Forebrain pathways modulate pain perception involving these two sensations
anxiety can increase pain perception
the placebo effect suppresses pain perception
There is correlation between anxiety level and degree of activation of that what
anterior cingulate cortex
This system is implicated in the placebo effect
endogenous opioid system; the perception of pain can be diminished when a patient believes they are taking medicine
Upon blocking of the endogenous opioid system, what happened to the pain levels
the pain levels felt increased
