Central Nervous System Tracts

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  • 7/23/2019 Central Nervous System Tracts

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    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

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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

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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

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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