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20 Cards in this Set

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Receptors of the pain pathways
non-encapsulated, free nerve endings
Nociceptors:
-associated with Asigma Fibers = FAST PAIN (localized, sharp)
-accociated with C fibers = SLOW PAIN (dull, throbbing)
Receptors of temperature pathways
Heat Receptors
Cold Receptors
likely some warming/cooling also
free nerve endings
pain and temperature information travels on what pathways?
ANTEROLATERAL SYSTEM (aka spinalthalamic) (**for MOST of the body)

TRIGEMINAL PAIN AND TEMPERATURE SYSTEM (for anterior 2/3 of head)
How do pain and temp fibers of CNVII, IX and X reach cortex?
cell bodies located in sensory ganglia associated with CNs (geniculate (VII), superior of (IX and X)) and central axon enters trigeminal pain and temperature system (in spinal tract of CNV)
ANTEROLATERAL SYSTEM is a pathway for what type of information?
PAIN/
TEMPERATURE/
CRUDE(light) touch
Describe path of pain in leg
1st Order: Nocireceptor, peripheral nerve, cell body in DRG, enters dorsal root, ascends DORSOLATERAL TRACT OF LISSAUER, synapses in dorsal horn (directly or indirectly)
2nd Order: decussate via anterior commissure, ascend to thalamus in STT, most synapse in VPL nucleus
3rd order: project through posterior limb of the internal capsule to the SI
Describe synapse between first and second order neurons of ALS Pathway
direct synapse at neurons of:
-Marginal zone or
-Substantia Gelatinosa

Indirect synapse in neurons of: -Lamina V
(via interneurons from substantia Gelatinosa)
where do fibers decussate in ALS Pathway
in the anterior white commissure of the spinal cord
where are the synapses in the ALS pathway?
1-->2 (DORSAL HORN: Marginal, Substania Gealtinosa or Lamina V)

2-->3 (mostly in VPL Nucleus of the Thalamus, some project elsewhere: involved in general arousal/emotional response)

3-->cortex (SI)
within the brainstem where are pain/temp fibers from the legs found?
in the lateral part of the SPINOTHALAMIC TRACT (stay lateral, but swing anteriorly as they ascend rostrally)
Explain basis for referred pain
afferent nociceptors from viscera, CONVERGE on same 2nd order cell bodies (of the ALS) as cutaneous nociceptors

brain cannot distinguish source of pain, often assumes cutaneous (much more frequent source of input, than viscera)
describe pathway of TRUE VISCERAL PAIN (as opposed to referred)
true visceral pain travels from nociceptors of viscera to synapse with 2nd order cell bodies in intermediate gray matter near the central canal that travel in the DC-ML
(these fibers conduct actual visceral pain sensations)
neurons in the pain-modulating pathways use what as neurotransmitters?
endogenous opiate peptides (enkephalins, endorphins, and dynorphins)

explains why opium derivatives are ANALGESTIC, mimic neurotransmitters thereby activating pain-modulating pathways
GATE THEORY OF PAIN
mechanosensory fibers (Aa and Ab) traveling with the smaller pain fibers (Ad and C) in the
dorsal roots. It is thought that when the large fibers are stimulated, they stimulate inhibitory interneurons in the dorsal horn
(why you rub/shake injured hand)
Damage to the STT will impair
pain, tempearture and touch ability, however fine touch would still be intact via the DC-ML system
Describe deficit if the ventrolateral column fibers are damaged on one side of the spinal cord (as in Brown-Sequard syndrome)
the sensory deficit will be contralateral inferior to the level of the v If the ventral part of the spinal cord is damaged (as in syringomyelia*), the anterior white commissure can be disrupted. This results in lesion (sometimes as many as 4-6 segments inferior to the lesion due to neurons traveling up the tract of Lissauer).
If the ventral part of the spinal cord is damaged (as in syringomyelia*), the anterior white commissure can be disrupted. This results in
bilateral loss of pain and temperature in the areas of the body that are supplied by the damaged segments. The resulting pattern of sensory loss is called suspended-dissociated loss (“suspended” because the area of the deficit is between two intact areas, and “dissociated” because only pain and temperature information is affected).
If a lesion occurs in the cerebral cortex, what sensory loss occurs?
all sensory modalities are lost except the perception of pain; localization of pain is lost. Therefore, it is thought the conscious perception of pain is mediated at subcortical levels, while localization of pain requires cortical input.
Crude touch is assessed by
lightly stroking the skin with a piece of cotton. The patient should be able to locate where the sensation is felt.
Pain is assessed by
applying a sharp object to the patients skin (pin prick) or pinching an area of skin (e.g. with forceps). The patient should be able to describe the quality of the sensation (sharp, dull) and its location.