2/9: Thermal Sensation and Nociception II Flashcards
Where are wide-dynamic range neurons found?
In the dorsal horn of the spinal cord
What do WDR neurons respond to?
All somatosensory modalities
What are WDR neurons normal sensitive to?
non-noxious stimuli UNLESS the stimulus is highly
noxious
What is allodynia?
perception of non-noxious stimuli as pain
When do some second order neurons increase their frequency of activiation?
Following prolonged discharge—”wind-up.” May continue, even after
the nociceptive stimulus is removed
What is the gate control theory of pain?
Activation of Alpha beta fibers from the same region
inhibits the Spinothalamic pathway and reduces
pain perception
The activation of alpha-beta fibers activates what?
An inhibitory interneuron
that causes post-synaptic inhibition of the
Second-order neuron for the Pain Pathway
- This inhibition leads to a weaker pain signal being
sent to the thalamus and somatosensory cortex
- This is the basis for how massage therapy and
TENS units work as a treatment for chronic pain
conditions and is why rubbing a painful region
makes it feel better
How does pain inhibit pain?
Stimulate pain in other regions of the body to inhibit pain (via GABA)
at second order, WDR, neurons in spinal cord (Diffuse Noxious Inhibitory Control (DNIC) or Conditioned Pain Modulation (CPM))
What does a second noxious stimulus lead to?
Activation of the PAG, nRM and RVM in the brainstem, which results in diffuse analgesic effect over the rest of the body
“Pain inhibits pain”
What are interneurons in the dorsal horn of the spinal cord activated by?
5-HT/NE and release endogenous opiates (enkephalin)
What does enkephalin in the dorsal horn inhibit?
the first-order and second-order neurons (nociceptive
specific and/or WDR neurons)
____________ is the selective suppression of pain without effects on consciousness or other sensations
Analgesia
What are mechanisms to achieve pain relief?
- Pharmacological agents: COX Inhibitors (aspirin,
ibuprofen), Opioids, Antidepressants (TCAs),
Anticonvulsants (GABApentin), Topical Lidocaine &
Capsaicin - Massage (Gate Control Theory of Pain)
- Acupuncture (seems to be linked to activation of the
endogenous opioid pathways) - Transcutaneous Electrical Stimulation (TENS)
- Nerve Blocks
How is pain information from the orofacial region conveyed into the CNS?
Via the Trigeminospinothalamic Tract and the
Trigeminoreticular Tract
Pain can be referred to the orofacial region (particularly
teeth) in response to:
- Maxillary Sinusitis
- Angina
- Migraine
- Nasal Mucosa
- Ear Pain
Why is dental pain exaggerated pain even with mild inflammation?
Dentin and enamel has limited space to swell in the inflammatory
state