Ascending Pathways Flashcards
what is somatotopy
somatotopy is ___ specific
what part of the brain represents a certain part of the body
correspondence of a specific area of the body to a specific areas in the brain and CNS
is location specific
first order neurons travel from the ___ to the ___
second order neurons travel from the ___ to the ___
third order neurons travel from the ___ to the ____
periphery to spinal cord
spinal cord/brainstem to thalamus
thalamus to primary sensory cortex
in second order neurons, where is the cell body located
what happens at the second order neuron
on the same side as the primary afferent
it crosses the midline
where is the cell body of the first order neuron located
where is the cell bod of the second order neuron located
in the dorsal root ganglion
in the dorsal horn in the spinal cord
what are the three categories of somatosensory receptors of primary afferents
mechanoreceptors, nociceptors, thermoreceptors
what is a dermatome
if there is an injury at the DRG what would you expect to see changes in
an area of the skin supplied by a single dorsal nerve root (has a specific pathway related to that level/region of the spinal cord)
sensory perception that’s equivalent to the area supplied by that dorsal nerve root
how do peripheral sensory nerve distributions and dermatomes differ
explain what we would see if there was damage to a peripheral sensory nerve vs injury to the dorsal root/dermatome
peripheral sensory nerve distributions supply a wider area of the body
damage to peripheral sensory nerve would cause sensory change in a larger/less specific area of the body (damage in the periphery before it reaches the DRG)
injury to the DRG would cause more specific sensory changes in a certain area of the skin (damage at spinal cord)
how does the cross section of the spinal cord differ by region (C, T, L, S)
white vs grey matter, cervical and lumbar enlargements, lateral horn
C: enlargement due to more cell bodies and information coming in from the arms
T: less grey matter due to no limbs, lateral horn located here which is the central component of the sympathetic division of the ANS
L: enlargement due to more cell bodies and information coming in from the legs, more white matter and more tracts
S: fewer tracts, less white matter and more grey matter
the cervical enlargements span which spinal cord segments
the lumbar enlargements span which spinal cord segments
the DCML is separated into ___ and ___ parts
C: C3-T2
L: L1-S3
medial and lateral
what is the medial and lateral portions of the DCML called
where are the spinocereballar tracts located in the spinal cord
where are the spinothalamic tracts located in the spinal cord
medial: fasciculus gracilis (lower extremity)
lateral: fasciculus cuneatus (upper extremity)
on the most lateral parts
on the anterior and lateral parts (also called anterolateral tract)
T or F: there is difference in somatotopy within ascending tracts in the spinal cord
what is the somatotopic organization of the cerebral cortex (legs vs arms, body parts that are largely represented)
T
the spinothalamic tract is organized from lateral to medial
the DCML tract is organized from medial to lateral
the legs and feet are medial to the arms, face and mouth are largely represented
what type of information does the DCML carry and how can we test each of these
discriminative touch: 2 point discrimination
vibration: tuning fork
proprioception: place limb into multiple positions and ask them where they perceive it to be with their eyes closed
DCML:
first order neuron: come from, travel to, along what pathway, cell body location
second order neuron: synapse with the first order, cross, travel to and in what pathway
third order neuron: synpase with second order, travel to, as what fibres
mechanoreceptors to the medulla along the dorsal column, DRG
synapses and crosses in medulla, travels to thalamus along the medial lemniscus
ventral posterolateral nucleus in thalamus to primary somatosensory cortex as thalamocortical fibres
damage to the dorsal column results in loss of what
damage to the medial lemniscus results in loss of what
ipsilateral discriminative touch, proprioception, vibration
contralateral discriminative touch, proprioception, vibration
DCML:
what is the somatotopy at the level of the spinal cord, medulla and cortex
spinal cord: LE medial to UE
medulla: LE lateral to UE
cortex: LE medial to UE
what type of information does the spinothalamic tract carry and how would we test each of these
pain: sharp and dull test
temperature: tube with warm or cold water
non discriminative touch and pressure: push finger into skin
spinothalamic:
first order: type of receptors carry info where, synapse location
second order: travel from, cross where, go to where
third order: travel from, go to where as what fibres
first order: nociceptors/thermoreceptors to the spinal cord then bifurcates, branch 1 synapse on dorsal horn at same level, branch 2 ascends/descends spinal cord 1-2 levels via lissauer’s fasciculus and synapses at dorsal horn
second order: from dorsal horn, cross at anterior white commissure, medulla
third order: VPL to primary somatosensory cortex and elsewhere as thalamocortical fibres
second order neurons synpase on a cell body that is on what side compared to the first order neuron
on the same side as the first order neuron
where are the nuclei for 2nd order neurons located in the dorsal horn of the spinothalamic tract
what type of information does the anterior and lateral tracts of the spinothalamic tract carry
when anterior and lateral tracts arrive at the medulla they merge to form what tract
substantia gelatinosa and nucleus propius
anterior: crude touch and pressure
lateral: pain and temperature
spinal lemniscus which then travels to the VPL
what is the NT for pain afferents
when is substance P released and what does this signal
glutamate
with higher frequency AP, signals moderate to severe pain
spinothalamic:
what is the somatotopy at level of the spinal cord, thalamus, cortex
spinal cord: LE lateral to UE
thalamus: LE lateral to UE
cortex: LE medial to UE
what type of information does the spinocerebellar tract carry
how many pathways does the spinocerebellar tract have
non conscious proprioception
4 (2 for upper, 2 for lower extremities)
name the 2 spinocerebellar pathways of the lower extremity
name the 2 spinocerebellar pathways of the upper extremity
lower: dorsal spinocerebellar (uncrossed), ventral spinocerebellar (crossed)
upper: cuneocerebellar (uncrossed), rostral spinocerebellar (crossed)
which tract has the largest fibres in the CNS
what purpose does this serve
spinocerebellar
fast conduction which supports the pathways main function of monitoring steady state reflex arcs, detecting errors/changes to motor plans
T or F: neuroplasticity change can occur at the level of the tracts
T
