martin chapter 5 Flashcards
pain, temperature and itch are mediated by which system?
anterolateral system
where is the anterolateral system first relay?
in the dorsal horn of the spinal cord
what are nociceptors?
sensory receptor neurons that are sensitive to noxious or tissue damaging stimuli and mediate pain. they respond to chemicals released from traumatized tissue
3 classes of nociceptors
- thermal
- mechanical
- polymodal
pruriceptors
-respond to histamine
-subclass of nociceptors because sensitive to noxious stimulation as well
name of receptor neurons sensitive to cold or warm
thermoreceptors
they detect changes in temperature within a normal physiological range
among the different membrane receptors that nociceptors have, for the transduction of noxious stimuli into depolarizing sensory potential we have a specific family of receptors that is very important:
TRP->Transient receptor potential receptors
type of axons of nociceptors, thermoreceptors and pruriceptors
small diameter axons
they can be both thinly myelinated (A-delta fibers) or non myelinated (C fibers)
nociceptors with A delta fibers mediate?
fast pain (initial sharp, prickling pain)
nociceptors with C fibers mediate?
slow pain (dull, burning, persistent)
fiber types of pruriceptors?
pruriceptors are C fibers only
hyperalgesia
exaggerated response to a noxious stimulus
allodynia
feeling pain to a stimulus that normally doesn’t produce pain
where do small diameter fibers (that subserve pain, temperature and itch) enter in the spinal cord?
in the lissauer tract. the white matter region that caps the dorsal horn
NB: this tract is lightly stained despite being white matter because the fibers are either thinly myelinated or non myelinated
what do neuron clusters in the spinal cord form?
rexed laminae
we have 10 rexed laminae
which laminae comprise the dorsal horn?
from lamina I to VI
which laminae comprise the ventral horn?
laminae VIII and IX
which laminae comprise the intermediate zone?
laminae VII and X
which lamina comprise the grey matter surrounding the central canal?
lamina X
decussation in the anterolateral system happens in?
the ventral (anterior) commissure, ventral to the central canal
Where are axons transmitting info from caudal segments located in the anterolateral system ( in respect to axons transmitting info from more rostral segments) ?
axons transmitting info from caudal segments are located lateral to axons transmitting info from more rostral segments
what is a spinal hemisection?
damage to one half of the spinal cord
why is the sensory loss contralateral to the side of the lesion in the anterolateral system?
because the axons of the anterolateral system decussate in the spinal cord
what is the reticular formation?
a heterogeneous collection of nuclei serving many somatic sensory, visceral, motor and regulatory function
where do the mechanosensory, the pain, the temperature and the itch projections terminate?
in the ventral posterior lateral nucleus. their terminal fields hardly overlap.the mechanosensory projections tend to be located rostral to the projections of pain, temperature and itch
where do the ventral medial posterior nucleus project?
in the insular cortex, which is important for perception of the quality and intensity of pain, temperature and itch and in mediating behavioral and autonomic responses
where do the medial dorsal nucleus project?
into the anterior cingulate gyrus, involved in the emotional aspects of somatic sensory stimulation
for acute pain there is the activation of multiple areas of the cerebral cortex termed “the pain matrix”. name these areas
-primary and secondary somatic sensory areas
-anterior cingulate cortex
-prefrontal cortex
-insular cortex
-some areas of the thalamus and the amygdala
among the cortical areas, which one is most consistently activated during painful stimuli?
the insular cortex
