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7/23/2019 Central Nervous System Tracts
1/4
Spinal Cord Sensory Function Level of
decussation/origin
Ascension/descens
ion
Target Spinal cord
lesionDorsal column-medial
lemniscus
proprioception,
fne touch
nucleus gracilis and
cuneatus in lower
medulla
ipsilateral in spinal
cord (asciculi) and
contralateral aterlower medulla
ventral
posterolateral
thalamic nucleussomatosensory
cortex
ipsilateral los
Anterolateral system pain,
temperature,
gross touch
dorsal horn @ level o
entry or slightly
abovebelow
contralateral ventral
posterolateral
thalamic nucleus
somatosensory
cortex
contralateral
loss
!osteriordorsal
spinocerebellar
proprioception
eedbac" rom
lower limbsbody
dorsal horn nucleus
dorsalis o #lar"e, does
not cross
ipsilateral cerebellum via
inerior cerebellar
peduncle
#uneocerebellar proprioception
eedbac" rom
upper limbsbody
nucleus cuneatus o
dorsal colum, does not
cross
ipsilateral cerebellum via
inerior cerebellar
peduncleAnteriorventral
spinocerebellar
proprioception
eedbac"rom
lower limbsbody
spinal border cells in
rim o ventral horn
contralateral but
crosses bac" over in
brainstem
cerebellum via
superior cerebellar
peduncleSpinal Cord Motor$ateral corticospinal
(direct)
limbfne motor pyramids contralateral lower motor
neurons in lateral
ventral horn
ipsilateral los
Anterior corticospinal(direct)
axialgross motor lower motor neurons,does %&' cross @
pyramids
ipsilateral butbilaterally innervates
target neurons
lower motorneurons in medial
ventral horn
no loss(bilateral)
ubrospinal
(indirect)
(mostly upper)
limb exor motor
(assists lateral
corticospinal)
red nucleus in midbrain contralateral lower motor
neurons
controlling (mostly
upper) limb exors'ectospinal
(indirect)
involuntary head
movement or
superior colliculus in
midbrain
contralateral lower motor
neurons in cervical
7/23/2019 Central Nervous System Tracts
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coordination w
eyes
spinal cord
controlling head
mm*$ateral vestibulospinal
(indirect)
reexively
stimulatesextensorsinhibits
exors (trip
reex)
lateral vestibular
nucleus in mid pons,does not cross
ipsilateral lower motor
neuronscontrolling limb
exors and
extensors+edial vestibulospinal
(indirect)
involuntary head
stabiliation
(assists
tectospinal)
medial vestibular
nucleus in mid pons
bilateral lower motor
neurons in cervical
spinal cord
controlling head
mm*!ontine reticulospinal
(indirect)
posturalinvolunt
ary control o
axial mm*
pontine reticular
ormation, does not
cross
ipsilateral lower (primarily
gamma) motor
neurons in medial
ventral horn+edullary
reticulospinal
(indirect)
posturalinvolunt
ary control o
limb mm*
medullary reticular
ormation
bilateral lower (primarily
gamma) motor
neurons in lateral
ventral hornBrain Stem Sensory!ontine
trigeminothalamic
fne touch above
nec"
pontine (chieprincipal)
trigeminal nucleus @
level o entry (pons)
contralateral ventral
posteromedial
thalamic nucleus
somatosensorycortex
+edullary
trigeminothalamic
pain,
temperature,
gross touch
above nec"
spinal trigeminal
nucleus in lower
medulla below level o
entry
descends in spinal
trigeminal tract to
reach spinal
trigeminal nucleus,
ascends
contralaterally in
trigeminothalamic
ventral
posteromedial
thalamic nucleus
somatosensory
cortex
7/23/2019 Central Nervous System Tracts
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tractBrain Stem Motor#orticonuclearcorticob
ulbar
voluntary fne
motor above
nec"
genu o internal capsue bilateral w
contralateral bias
(contralateral only
on lower motor
neurons in lower .
o ace)
motor nuclei o
cranial nn* except
///, /0, and 0/ (eye
motor)
1aw 1er" reex
(bilateral,
monosynaptic)
mesencephalic nucleus o 0 relays (wo synapse)
proprioceptive impulses rom muscle spindle o masseter
m* to motor nucleus o 0 bilaterally
motor nucleus o 0
(to masseter m*)
corneal blin" reex(bilateral,
polysynaptic)
cornea gross touch relayed down spinal trigeminal tract,synapses on second order interneuron, synpases on third
order motor nucleus o 0// bilaterally
motor nucleus o 0//(to orbicularis oculi m*)
in 02 primaryneuron a3ects bot
eyes, in 0// third
order neuron
a3ects only one
eye
/4 4 0//!arasympathetic
(preganglionic)
column
506
inerior salivatory nucleus
otic ganglion parotid
gland
dorsal motor nucleus o 4
parasympathetic ganglia
smooth m*, glands o viscera
superior salivatory
nucleus
submandibularpterygop
alatine ganglion
submandibular and
sublingual
glandslacrimal and nasalmucus glands
7ensory column
70A and 50A
taste rom posterior 2 o
tonguerostral nucleus
solitarius (70A)
carotid body and visceral
sensation rom pharynx,
larynx, and posterior tongue
caudal nucleus solitarius
(50A)
taste rom base o
tongueepiglottisrostral
nucleus solitarius (70A)
sensation rom viscera caudal
nucleus solitarius (50A)
taste rom anterior 8 o
tonguerostral nucleus
solitarius (70A)
9ranchial motor
column
706
nucleus ambiguus motor
to stylopharyngeus m*
nucleus ambiguus (branchial)
mm* o pharynx and larynx
motor nucleus o 0//
internal genu wraps
around nucleus o 0/
(branchial) mm* o acial
expression
7/23/2019 Central Nervous System Tracts
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Dorsal thalamic divison Cortical associaitonventral anterior nucleus motoranterior nuclei limbiclateral dorsal nucleus limbicmedial dorsal nucleus rontal associationlateral posterior nucleus multimodal sensory associationpulvinar multimodal sensory associationmedial geniculate nucleus auditorylateral geniculate nucleus visualventral posterolateral nuclei somatosensory (D#-+$ and A$7)ventral posteromedial nuclei somatosensory (trigeminothalamic)ventral lateral nucleus motor
Internal capsule divison Cortical association
genu corticonuclear tractanterior limb rontal lobeposterior limb parietal loberetrolenticular limb occipital lobesublenticular limb temporal lobe
'he lateral one o the : is where spinoreticular tracts enter carrying somatic pain and visceral sensation
'he medial one o the : is where the pontine and medullary reticulospinal tracts arise
'he median one o the : is where the raphe nuclei are that produce serotonin, pro1ect to spinal cord and mediate
central analgesia (gating o pain)
9ranches o basilar, vertebral, and ant* spinal aa* supply medial brain stem* Anything ;cerebellar< supplies lat* brainstem*
=pper motor neuron lesion > paralysis o contralateral lower ? o ace (still have ipsilateral to upper ace)
$ower motor neuron lesion > total paralysis o contralateral ace
7yringomyleia a3ects anterior white commissure fbers (so bilateral loss o pain, temp, gross touch)
'hird ventricle orms medial boundary o diencephalon internal capsule orms lateral boundary