Pain Flashcards
Allodynia
Abnormal perception of pain from a stimulus that shouldn’t be painful
Dysesthesia
Not pain. Just an uncomfortable sensation.
Anesthesia
Reduced perception of ALL sensation, mainly touch
Pallanesthesia
Loss of perception of vibration
Causalgia
Burning pain in the distribution of one or more peripheral nerves
Protopathic sensation
noxious
Epicritic sensation
Non-noxious sensation
Cancer pain involves both
acute and chronic pain
These types of pain use both pain pathways
Thermal and mechanical
This pain uses mostly slow fibers
Chemical pain. Mediated by the following NTs
Bradykinin
Substance P
Proteolytic enzymes
All of this increase the permeability of ions
Nociception involves these four processes
Transduction
Transmission
Modulation
Perception
Modulation
Neurons originating in the brainstem descend to the level of the spinal cord, releasing substances to modulate the nociceptive impulses
First order neurons
Send axons via the dorsal root ganglia, and then synapse with interneurons, sympathetic neurons, motor neurons (ventral horn), or second order neurons.
Neurons traveling along the STT may end up in the
Thalamus
RF
Nucleus raphe magnus
Periaqueductal gray
Where is the STT?
Anterolaterally in the white matter of the spinal cord
Third order neurons
Send fibers from the thalamus to:
Somatosensory areas I and II in the parietal cortex
Superior wall of the sylvian fissure
Tracks alternative to the STT
1) Spinoreticular (will cause insomnia)
2) Spinomesencephalic (activates the antinociceptive, descending pathways. It mediates the pain!)
3) Spinohypothalamic and spinotelencephalic (activate the hypothalamus to evoke emotional behavior)
Fast pain pathway (neospinothalamic tract)
1st order- via A-delta to lamina I (lamina marginalis) on the dorsal horn of spinal cord
2nd order- Decussate through the anterior white commisure, and and pass up through the white anterolateral columns (STT)
Some of these will end on the reticular formation (nag you enough not to fall asleep), but most will end on the ventrobasal complex (VBC) of the thalamus
3rd order then communicate with somatosensory cortex
Slow pain pathway (paleospinothalamic tract)
1at order- via C fibers to laminae II and III (substantia gelatinosa)
2nd order- either connect II or III to V within the dorsal horn
3rd order- now connect with the fast pain pathway, by decussating via the anterior white commissure, and traveling up the STT
Where do the 3rd order neurons terminate?
10% in thalamus
Rest go to pons, midbrain, and the tectum of the midbrain mesencephalon periaqueductal grey
When is fast pain easily localized?
If the a-delta fibers are stimulated long with tactile receptors
3 major components of the brain analgesia system
1) Periaqueductal grey (in the midbrain)
2) Nucleus raphe magnus (in the medulla)
3) Nociceptive inhibitory neurons in the dorsal horn of the spinal cord (work to inhibit those neurons carrying pain signals)