21-Spinal Cord Tracts I

7/24/2019 21-Spinal Cord Tracts I

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Sensory & MotorSensory & Motor

PathwaysPathways

Dr. Zeenat ZaidiDr. Zeenat Zaidi


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There is a continuous flow of information between theThere is a continuous flow of information between the

brain, spinal cord, and peripheral nerves.brain, spinal cord, and peripheral nerves. ThisThis

information is relayed by sensory (ascending) andinformation is relayed by sensory (ascending) andmotor (descending) pathways.motor (descending) pathways.

Generally the pathways:Generally the pathways:

onsists of a chain ofonsists of a chain of tracts,tracts,associatedassociated nucleinucleiandand

varying number of relays (varying number of relays (synapsessynapses)) onsist of two or three neuronsonsist of two or three neurons

!"hibit somatotopy (precise spatial relationships)!"hibit somatotopy (precise spatial relationships)

#ecussate#ecussate

$nvolve both the brain and spinal cord$nvolve both the brain and spinal cord

%re paired (bilaterally and symmetrically)%re paired (bilaterally and symmetrically)


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Somatic Sensory PathwaysSomatic Sensory Pathways


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Sensory Pathways

&onitor conditions both inside the body and in the&onitor conditions both inside the body and in thee"ternal environmente"ternal environment 'ensationstimulated receptor passes information to'ensationstimulated receptor passes information to

the ' via afferent (sensory) fibersthe ' via afferent (sensory) fibers

&ost sensory information is processed in the spinal&ost sensory information is processed in the spinalcord , thalamus, or brain stem. *nly + reaches thecord , thalamus, or brain stem. *nly + reaches thecerebral corte" and our conscious awarenesscerebral corte" and our conscious awareness

-rocessing in the spinal cord can produce a rapid-rocessing in the spinal cord can produce a rapid

motor response (stretch refle")motor response (stretch refle") -rocessing within the brain stem may result in-rocessing within the brain stem may result in

comple" motor activities (positional changes in thecomple" motor activities (positional changes in theeye, head, trun)eye, head, trun)


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Sensory Pathways ontain a se/uence ofontain a se/uence of T01!!T01!!

neuronsneuronsfrom the receptor to thefrom the receptor to thecerebral corte"cerebral corte" First order neuron:First order neuron: 'ensory'ensory

neuron that delivers informationneuron that delivers informationfrom the receptor to the '.from the receptor to the '.

ell body located in the dorsalell body located in the dorsalroot ganglion. The %"on (centralroot ganglion. The %"on (centralprocess)process) passes to the spinalpasses to the spinalcord through the dorsal root ofcord through the dorsal root ofspinal nervespinal nervegives manygives manycollaterals which tae part incollaterals which tae part inspinal cord refle"esspinal cord refle"esrunsrunsipsilaterallyipsilaterallyand synapses withand synapses withsecondorder neurons in thesecondorder neurons in thecord and medulla oblongatacord and medulla oblongata

11

22

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'econd order neuron:'econd order neuron: 0as cell body in the0as cell body in the

spinal cord or medullaspinal cord or medullaoblongataoblongata%"on decussate%"on decussate 22 Terminate on 3rd orderTerminate on 3rd order

neuronneuron

Third order neuron:Third order neuron: 0as cell body in0as cell body in

thalamusthalamus%"on terminates on%"on terminates on

cerebral corte"cerebral corte"ipsilaterallyipsilaterally


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White Matter: PathwayWhite Matter: Pathway

GeneralizationsGeneralizations

%scending and descending fibers are organi4ed in%scending and descending fibers are organi4ed indistinct bundles which occupy particular areas anddistinct bundles which occupy particular areas and

regions in the white matterregions in the white matter

GenerallyGenerally long tractslong tracts are located peripherally in the whiteare located peripherally in the white

matter, whilematter, while shorter tractsshorter tracts are found near the grayare found near the gray

mattermatter

5 The TRACTis a bundle of nerve fibers (within ')

having the same origin, course, destination 2

function5 The name of the tract indicates the origin and

destination of its fibers

5 The a"ons within each tract are grouped according

to the body region innervated


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Tracts of the SpinalTracts of the Spinal

CordCord

Tracts that serve to 6oin brain to the spinalTracts that serve to 6oin brain to the spinalcordcord %scending%scending #escending#escending

7ibers that interconnect ad6acent or distant7ibers that interconnect ad6acent or distantsegments of the spinal cordsegments of the spinal cord $ntersegmental$ntersegmental(propriospinal)(propriospinal)


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nterse!mental Tractsnterse!mental Tracts !"tensive fiber connections!"tensive fiber connections

between spinal segmentsbetween spinal segments Fasciculus propriusFasciculus proprius

'hort ascending 2'hort ascending 2descending fibersdescending fibers

8oth crossed 28oth crossed 2uncrosseduncrossed 8egin and end within the8egin and end within the

spinal cordspinal cord -articipate in-articipate in

intersegmental spinalintersegmental spinalrefle"esrefle"es

-resent in all funiculi-resent in all funiculiad6acent to gray matterad6acent to gray matter


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Intersegmental Tracts Dorsolateral tract ofDorsolateral tract of

Lissauer:Lissauer: -rimary sensory-rimary sensoryfibers carryingfibers carrying pain,pain,

temperature and touchtemperature and touch

information bifurcate uponinformation bifurcate upon

entering the spinal cord. Theirentering the spinal cord. Their

branches ascend and descendbranches ascend and descendfor several spinal segments infor several spinal segments in

the dorsolateral tract, beforethe dorsolateral tract, before

synapsing in the dorsal hornsynapsing in the dorsal horn

$ntersegmental fibers, establishing connections with

neurons in the opposite half of the spinal cord, cross

the midline in the anterior white commissure


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Ascending Spinal Tracts

Transmit impulses: oncerned with specific sensory modalities:

pain, temperature, touch, proprioception, thatreach a conscious level (cerebral corte") #orsal column funiculi 'pinothalmic tracts

7rom tactile and stretch receptors to

subconscious centers(cerebellum) 'pinocerebellar tracts


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Three ma6or pathways carry sensory informationThree ma6or pathways carry sensory information

-osterior column pathway (gracile 2 cuneate-osterior column pathway (gracile 2 cuneate

fasciculi)fasciculi) %nterolateral pathway (spinothalamic)%nterolateral pathway (spinothalamic)

'pinocerebellar pathway'pinocerebellar pathway


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Ascending Spinal Tracts

#orsal white column#orsal white column 9ateral spinothalamic9ateral spinothalamic

%nterior spinothalamic%nterior spinothalamic

%nterior spinocerebellar%nterior spinocerebellar

-osterior spinocerebellar-osterior spinocerebellar uneocerebellaruneocerebellar

'pinotectal'pinotectal

'pinoreticulr'pinoreticulr

'pinoolivary'pinoolivary

isceral sensory tractsisceral sensory tracts


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Dorsal Col"mnDorsal Col"mn Contains two tracts,Contains two tracts, FasciculusFasciculus

gracilis (FG)gracilis (FG)&& asciculusasciculuscuneatus (FC)cuneatus (FC)

Carry impulses concerned withCarry impulses concerned with

proprioception andproprioception and

discriminati!e touch romdiscriminati!e touch rom

ipsilateralipsilateralside o "odyside o "ody

Contain the a#ons oContain the a#ons o primaryprimary

a$erent neuronsa$erent neuronsthat ha!ethat ha!e

entered cord through dorsalentered cord through dorsal

roots o spinal ner!esroots o spinal ner!es

FGcontains %"ers recei!ed at sacral, lum"ar andlower thoracicle!els, FCcontains %"ers recei!ed atupper thoracic and cer!ical le!els


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7ibers ascend without7ibers ascend withoutinterruption where they terminateinterruption where they terminateuponupon ;;ndndorder neuronsorder neuronsininnucleus gracilis and nucleusnucleus gracilis and nucleuscuneatuscuneatus

The a"ons of the ;The a"ons of the ;ndndorderorderneuronsneurons decussatedecussatein thein themedulla asmedulla as internal arcuate fibersinternal arcuate fibersand ascend through the brainand ascend through the brainstem asstem as medial lemniscusmedial lemniscus..

The medial lemniscus terminatesThe medial lemniscus terminatesin thein the ventral posterior nucleus ofventral posterior nucleus ofthe thalamusthe thalamusuponupon 33rdrdorderorderneuronsneurons, which pro6ect to the, which pro6ect to thesomatosensory corte"somatosensory corte"(thalamocortical fibers)(thalamocortical fibers)


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Spinothalamic TractsSpinothalamic Tracts 9ocated lateral and ventral to9ocated lateral and ventral to

the ventral hornthe ventral horn arry impulses concernedarry impulses concerned

withwith painpain andand thermalthermalsensationssensations (lateral tract)(lateral tract)andandalsoalso non discriminativenon discriminativetouchtouchandand pressurepressure (medial(medial

tract)tract) 7ibers of the two tracts are7ibers of the two tracts are

intermingled to some e"tentintermingled to some e"tent $n brain stem, constitute the$n brain stem, constitute the

spinal lemniscusspinal lemniscus 7ibers are highly somato7ibers are highly somato

topically arranged, with thosetopically arranged, with thosefor thefor the lower limblower limblying mostlying mostsuperficiallysuperficially and those for theand those for theupper limbupper limblyinglying deeplydeeply

Information is sent to the

primary sensory cortex on

the opposite side of the body


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#ateral Spinothalamic Tract#ateral Spinothalamic Tract arries impulses concernedarries impulses concerned

withwith painpainandand thermalthermalsensations.sensations.

%"ons of +%"ons of +stst order neuronsorder neuronsterminate in the dorsal hornterminate in the dorsal horn

%"ons of ;%"ons of ;ndndorder neuronorder neuron(mostly in the(mostly in the nucleusnucleuspropriusproprius),), decussate withindecussate withinone segmentone segmentof their origin, byof their origin, bypassing through the ventralpassing through the ventral

white commissure 2 terminatewhite commissure 2 terminateon 3on 3rdrdorder neurons inorder neurons in ventralventralposterior nucleusposterior nucleusof theof thethalamusthalamus

Thalamic neurons pro6ect toThalamic neurons pro6ect to

thethe somatosensory corte"somatosensory corte"


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$nterior Spinothalamic Tract$nterior Spinothalamic Tract

arries impulses concernedarries impulses concerned

withwith non discriminative touchnon discriminative touchandand pressurepressure %"ons of +%"ons of +stst order neuronsorder neurons

enter cord terminate in theenter cord terminate in thedorsal horndorsal horn

%"ons of ;%"ons of ;ndnd

order neuronorder neuron(mostly in the(mostly in the nucleusnucleuspropriusproprius)) may ascend severalmay ascend severalsegments before crossingsegments before crossingtotoopposite side by passingopposite side by passingthrough the ventral whitethrough the ventral white

commissure 2 terminate on 3commissure 2 terminate on 3rdrdorder neurons inorder neurons in ventralventralposterior nucleusposterior nucleusof theof thethalamusthalamus

Thalamic neurons pro6ect toThalamic neurons pro6ect to

thethe somatosensory corte"somatosensory corte"


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Spino%retic"lo%thalamic SystemSpino%retic"lo%thalamic System

The system represents an additional routeThe system represents an additional routeby whichby which dull, aching paindull, aching painis transmitted tois transmitted to

a conscious levela conscious level

'ome'ome ;;ndnd

order neuronsorder neuronsterminate in theterminate in thereticular formationreticular formationof the brain stem,of the brain stem,

mainly within the medullamainly within the medulla

1eticulothalamic fibers1eticulothalamic fibersascend toascend tointralaminar nuclei of thalamusintralaminar nuclei of thalamus, which in, which in

turn activate the cerebral corte"turn activate the cerebral corte"


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Spinocereellar TractsSpinocereellar Tracts

The spinocerebellar systemThe spinocerebellar system

consists of a se/uence ofconsists of a se/uence ofonlyonly two neuronstwo neurons Two tracts:Two tracts: -osterior-osterior22

%nterior%nterior 9ocated near the9ocated near the

dorsolateral and ventrolateraldorsolateral and ventrolateralsurfaces of the cordsurfaces of the cord ontain a"ons of theontain a"ons of the secondsecond

order neuronsorder neurons arry information derivedarry information derived

from muscle spindles, Golgifrom muscle spindles, Golgitendon organs and tectiletendon organs and tectilereceptors to the cerebellumreceptors to the cerebellumfor the control of posture andfor the control of posture andcoordination of movementscoordination of movements

P t i S i llPosterior Spinocereellar


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Posterior SpinocereellarPosterior Spinocereellar

TractsTracts -resent only above level-resent only above level

9393 The cell bodies of ;The cell bodies of ;ndnd

order neuron lie inorder neuron lie in larslars

columncolumn

%"ons of ;%"ons of ;ndndorder neuronorder neuron

terminateterminate ipsilaterallyipsilaterally

(uncrossed) in the(uncrossed) in the

cerebellar corte"cerebellar corte"bybyentering through theentering through the

inferior cerebellarinferior cerebellar

pedunclepeduncle


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'entral Spinocereellar Tracts'entral Spinocereellar Tracts The cell bodies of ;The cell bodies of ;ndndorder neuronorder neuron

lie inlie in base of the dorsal hornbase of the dorsal hornof theof thelumbosacral segmentslumbosacral segments

%"ons of ;%"ons of ;ndndorder neuronorder neuron crosscrosstoto

opposite side, ascend as far asopposite side, ascend as far as

the midbrain, and then mae athe midbrain, and then mae asharp turn caudally and enter thesharp turn caudally and enter the

superior cerebellar pedunclesuperior cerebellar peduncle

The fibers cross the midline for aThe fibers cross the midline for a

second time within the cerebellumsecond time within the cerebellum

before terminating in thebefore terminating in the

cerebellar corte"cerebellar corte"

8oth spinocerebellar tracts convey8oth spinocerebellar tracts convey

sensory information to the samesensory information to the same

side of the cerebellumside of the cerebellum


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Spinotectal TractSpinotectal Tract

%scends in the anterolateral%scends in the anterolateralpart in close association withpart in close association withspinothalamic systemspinothalamic system

-rimary afferents reach dorsal-rimary afferents reach dorsalhorn through dorsal roots andhorn through dorsal roots and

terminate onterminate on ;;ndnd

order neuronsorder neurons TheThe cell bodies of ;cell bodies of ;ndndorderorder

neuron lie inneuron lie in base of the dorsalbase of the dorsalhornhorn

%"ons of ;%"ons of ;ndndorder neuronorder neuroncross to opposite sidecross to opposite side, and, andpro6ect to thepro6ect to the peria/uiductalperia/uiductalgray matter and superiorgray matter and superiorcolliculuscolliculusin the midbrainin the midbrain


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Spino % oli(ary TractSpino % oli(ary Tract

$ndirect spinocerebellar pathway (spino

olivocerebellar)

$mpulses from the spinal cord arerelayed to the cerebellum via inferior

olivary nucleus

onveys sensory information to thecerebellum

7ibers arise at all level of the spinal cord


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Spinoretic"lar TractSpinoretic"lar Tract

*riginates in laminae $*riginates in laminae $

$$$$$$

ontainsontains uncrosseduncrossed

fibers that end infibers that end in

medullary reticularmedullary reticularformationformation 22crossed 2crossed 2

uncrossed fibers thatuncrossed fibers that

terminate in pontineterminate in pontine

reticular formationreticular formation 7orm part of the7orm part of the

ascending reticularascending reticular

activating systemactivating system


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Somatic Motor PathwaysSomatic Motor Pathways


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Motor PathwaysMotor Pathways ' issues motor commands in response to' issues motor commands in response to

information provided by sensory systems, sent byinformation provided by sensory systems, sent bythe somatic nervous system ('') and thethe somatic nervous system ('') and theautonomic nervous system (%')autonomic nervous system (%')

onscious and subconscious motor commandsonscious and subconscious motor commands

control seletal muscles by traveling over 3control seletal muscles by traveling over 3integrated motor pathwaysintegrated motor pathways TheThe corticospinalcorticospinalpathwaypathway< voluntary control of< voluntary control of

motor activitymotor activity

orticobulbar tractsorticobulbar tracts orticospinal tractsorticospinal tracts TheThemedialmedial andand laterallateralpathwayspathways< modify or direct< modify or direct

seletal muscle contractions by stimulating,seletal muscle contractions by stimulating,

facilitating, or inhibiting lower motor neuronsfacilitating, or inhibiting lower motor neurons


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Motor PathwaysMotor Pathways5 ontain a se/uence ofontain a se/uence of T=*T=*

neuronsneuronsfrom the cerebralfrom the cerebralcorte" or brain stem to thecorte" or brain stem to the

musclesmuscles5 >pper motor neuron>pper motor neuron: has cell: has cell

body in the cerebral corte" orbody in the cerebral corte" or

brain stem, a"onbrain stem, a"on decussatesdecussatesbefore terminating on the lowerbefore terminating on the lower

motor neuronmotor neuron5 9ower motor neuron9ower motor neuron: has cell: has cell

body in the ventral horn of thebody in the ventral horn of thespinal cord, a"on runs in thespinal cord, a"on runs in the

ipsilateralipsilateralventral root of theventral root of the

spinal nerve and supply thespinal nerve and supply the

muscle.muscle.

UMN

LMN


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escending Spinal Tracts

*riginate*riginatefrom thefrom the cerebral corte"cerebral corte"22 brainbrainstemstem

oncernedoncernedwith:with:

ontrol of movementsontrol of movements &uscle tone&uscle tone

'pinal refle"es 2 e/uilibrium'pinal refle"es 2 e/uilibrium

&odulation of sensory transmission to&odulation of sensory transmission tohigher centershigher centers

'pinal autonomic functions'pinal autonomic functions


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The motor pathways areThe motor pathways are

divided into two groupsdivided into two groups #irect pathways#irect pathways

(voluntary motion(voluntary motion

pathways) pathways) thethe

pyramidal tractspyramidal tracts $ndirect pathways$ndirect pathways

(postural pathways)(postural pathways),,

essentially all others essentially all others the e"trapyramidalthe e"trapyramidal

pathwayspathways


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Direct )Pyramidal* SystemDirect )Pyramidal* System

1egulates fast and fine (silled) movements1egulates fast and fine (silled) movements *riginate in the pyramidal neurons in the*riginate in the pyramidal neurons in theprecentral gyri,precentral gyri,

$mpulses are sent through the$mpulses are sent through the corticospinalcorticospinal

tractstracts and synapse in the anterior hornand synapse in the anterior horn 'timulation of anterior horn neurons activates'timulation of anterior horn neurons activates

seletal musclesseletal muscles -art of the direct pathway, called-art of the direct pathway, called corticobulbarcorticobulbar

tractstracts, innervates cranial nerve nuclei, innervates cranial nerve nuclei

ndirect )+,trapyramidal*ndirect )+,trapyramidal*


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ndirect )+,trapyramidal*ndirect )+,trapyramidal*

SystemSystem

omple" and multisynaptic pathwaysomple" and multisynaptic pathways The system includes:The system includes:

5 1ubrospinal tracts1ubrospinal tracts: control fle"or muscles: control fle"or muscles

5

estibulospinal tractsestibulospinal tracts: maintain balance and: maintain balance andpostureposture

5 Tectospinal tractsTectospinal tracts: mediate head nec, and eye: mediate head nec, and eye

movementmovement

5 1eticulospinal tracts1eticulospinal tracts


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Descendin! Spinal TractsDescendin! Spinal Tracts

-yramidal-yramidal orticospinalorticospinal

!"trapyramidal!"trapyramidal 1ubrospinal1ubrospinal

TectospinalTectospinal estibulospinalestibulospinal

*livospinal*livospinal

1eticulospinal1eticulospinal

#escending#escending

%utonomic 7ibers%utonomic 7ibers


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Corticospinal Tracts

oncernedoncernedwithwith

voluntary, discrete, silledvoluntary, discrete, silled

movements, especiallymovements, especially

those of distal parts of thethose of distal parts of the

limbs (fractionatedlimbs (fractionated

movements)movements) $nnervate$nnervate thethe

contralateral side of thecontralateral side of the

spinal cordspinal cord

-rovide-roviderapid directrapid directmethod for controllingmethod for controlling

seletal muscleseletal muscle


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*rigin*rigin: motor and sensory: motor and sensory

corticescortices

%"ons pass through%"ons pass through coronacorona

radiataradiata,, internal capsuleinternal capsule,, cruscrus

cerebricerebri andand pyramidpyramidofof

medulla oblongatamedulla oblongata $n the caudal medulla about$n the caudal medulla about

?@AB?@ABof the fibersof the fibersdecussatedecussateand form theand form thelateral corticospinal tractlateral corticospinal tract

1est of the fibers remain1est of the fibers remain

ipsilateralipsilateraland formand form anterioranteriorcorticospinal tractcorticospinal tract. They. Theyalso decussate beforealso decussate beforeterminationtermination


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#istribution#istribution:: @@ terminate at@@ terminate at

cervicalcervicalregionregion ;B at;B at thoracicthoracic ;@ at;@ at lumbosacrallumbosacral

levellevel

TerminationTermination:: entral hornentral hornneuronsneurons(mostly through(mostly throughinterneurons, a few fibersinterneurons, a few fibersterminate directly)terminate directly)

Corticobulbar tractsendend

at the motor nuclei of sat the motor nuclei of sof the contralateral sideof the contralateral side


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-"rospinal Tract-"rospinal Tract ontrolsontrols the tone of limbthe tone of limb

fle"or muscles, beingfle"or muscles, beinge"citatory to motor neuronse"citatory to motor neurons

of these musclesof these muscles

*rigin*rigin: 1ed nucleus: 1ed nucleus

%"ons course ventro%"ons course ventromedially, cross inmedially, cross in ventralventral

tegmental decussationtegmental decussation,,

descend in spinal corddescend in spinal cord

ventral to the lateralventral to the lateralcorticospinal tractcorticospinal tract

orticorubrospinal pathwayorticorubrospinal pathway

(!"trapyramidal)(!"trapyramidal)


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Tectospinal Tract &ediates refle" movements of&ediates refle" movements of

the head and nec in responsethe head and nec in responseto visual stimulito visual stimuli

*rigin*rigin: 'uperior colliculus: 'uperior colliculus

%"ons course ventromedially%"ons course ventromedially

around the peria/ueductal grayaround the peria/ueductal graymatter, cross inmatter, cross in dorsaldorsal

tegmental decussationtegmental decussation,,

descend in spinal cord near thedescend in spinal cord near the

ventral median fissure,ventral median fissure,

terminate mainly interminate mainly in cervicalcervical

segmentssegments

orticotectospinal pathwayorticotectospinal pathway

(!"trapyramidal)(!"trapyramidal)


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'esti"ulospinal Tracts 9ateral estibulospinal9ateral estibulospinal

TractsTracts *rigin*rigin:: lateral vestibularlateral vestibular

(#eiters) nucleus(#eiters) nucleus

%"ons descend%"ons descend ipsilaterallyipsilaterallyinin

the ventral funiculusthe ventral funiculus Terminate on ventral hornTerminate on ventral horn

cells throughout the length ofcells throughout the length of

spinal cordspinal cord

0as e"citatory influences0as e"citatory influencesupon e"tensor motor neurons,upon e"tensor motor neurons,

control e"tensor muscle tonecontrol e"tensor muscle tone

in the antigravity maintenancein the antigravity maintenance

of postureof posture


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'esti"ulospinal Tracts

&edial vestibulospinal&edial vestibulospinal

tracttract *rigin*rigin::medial vestibularmedial vestibular

nucleusnucleus

%"ons descend%"ons descend bilaterallybilaterallyinin

the ventral funiculus, with thethe ventral funiculus, with the

medial longitudinal fasciculusmedial longitudinal fasciculus

&ost of the fibers end in the&ost of the fibers end in the

cervical region, some reachingcervical region, some reaching

upper thoracic segmentsupper thoracic segments $nvolved in movements of the$nvolved in movements of the

head re/uired for maintaininghead re/uired for maintaining

e/uilibriume/uilibrium


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eticulospinal Tracts

$nfluence$nfluencevoluntary movement,voluntary movement,

refle" activity and muscle tone byrefle" activity and muscle tone bycontrolling the activity of bothcontrolling the activity of bothalpha and gamma motor neuronsalpha and gamma motor neurons

&ediate pressor and depressor&ediate pressor and depressoreffect on the circulatory systemeffect on the circulatory system

%re involved in control of breathing%re involved in control of breathing *rigin*rigin: pontine 2 medullary: pontine 2 medullary

reticular formationreticular formation &edial (pontine) reticulospinal&edial (pontine) reticulospinal

tract descendstract descends ipsilaterallyipsilaterally 9ateral (medullary) reticulospinal9ateral (medullary) reticulospinal

tract descendstract descends bilaterallybilaterally 8oth tracts located in the ventral8oth tracts located in the ventral

funiculusfuniculus


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escending Autonomic Fi"ers

The higher centersThe higher centers

associated with the control ofassociated with the control of

autonomic activity areautonomic activity are

situated mainly in thesituated mainly in the

hypothalmaushypothalmaus

The fibers run in theThe fibers run in thereticulospinal tractsreticulospinal tracts

Terminate on theTerminate on the autonomicautonomic

neuronsneuronsin the lateral horn ofin the lateral horn of

thoracic 2 upper lumbarthoracic 2 upper lumbar(sympathetic) and sacral(sympathetic) and sacral

segments (parasympathetic)segments (parasympathetic)

levels of the spinal cordlevels of the spinal cord

##


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21-Spinal Cord Tracts I

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