Thalamus Hypothalamus [Repaired].pdf

8/14/2019 Thalamus Hypothalamus [Repaired].pdf

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Neuroanatomy

ThalamusandHypothalamus

Objectives

Toreviewaverycomplexareaofthenervoussystemandtoemphasizethatthethalamusliesatthecenterofmanyafferentandefferentneuronalloopstootherpartsofthenervoussystem

Tolearnthelocationandboundariesofthehypothalamusandthevariousnucleithatmakeupthisimportantarea

Toreviewthemainconnectionsofthenuclei,

especially

the

connections

between

the

hypothalamus

andthepituitarygland

Toreviewsomeofthecommonclinicalproblemsinvolvingthehypothalamus


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Diencephalon

thediencephalon,orinbetweenbrain,iscompletelysurroundedbythecerebralhemispheresexceptatitsventralsurface

islimitedposteriorlybytheposteriorcommissureandanteriorlybythelaminaterminalis andtheforamenofMonro

posteriorlimboftheinternalcapsulelimitsthediencephalonlaterally

medially,thediencephalonformsthelateralwallofthethirdventricle

dorsalsurfaceformsthefloorofthelateralventricleandismarkedmediallybyabandofnervefibers,thestria medullaris thalami

ventralsurfacecontainshypothalamicstructures

agrooveextendingbetweentheforamenofMonro andtheaqueductofSylvius (thehypothalamicsulcus)dividesthediencephalonintoadorsalportion,thethalamus,andaventralportion,thehypothalamus

thetwothalamiareconnectedacrossthemidlineinabout70percentof

humansthrough

the

interthalamic adhesion

(massa intermedia)

diencephalondevelopsfromthecaudalvesicleoftheembryologicprosencephalon

Dorsalsurfaceofthediencephalon.Thalamiarelocatedonbothsidesofthethird

ventricle.Thestria medullaris thalamirepresentacomponentoftheepithalamus.


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Schematicdiagramshowingthesubdivisionsofthediencephalonasseenina

compositecoronalview

Diencephalon Thalamus

Ventralnucleargroup

Lateralgroupofthalamicnuclei

Medialgroup

Intralaminar nuclei

Midlinenuclei

Ventralthalamus

Hypothalamus Hypothalamicafferents

Hypothalamicefferents

Pituitarygland(hypophysis cerebri)

Epithalamus

Subthalamus


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THALAMUS

Thalamus

attherostralendofthebrainstem

functionsasanimportantrelayand

integrativestationforinformation

cerebralcortex

basalganglia

Hypothalamus

brainstem


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Generalappearance

large,eggshapedmassofgraymatterthatformsthemajorpartofthediencephalon

twothalami,andoneissituatedoneachsideofthethirdventricle

Borders anteriorendofthethalamusisnarrowandroundedandformsthe

posteriorboundaryoftheinterventricular foramen

posteriorendisexpandedtoformthepulvinar,whichoverhangsthesuperiorcolliculus

Inferiorsurfaceiscontinuouswiththetegmentum ofthemidbrain

medialsurfaceofthethalamusformspartofthelateralwallofthethirdventricleandisusuallyconnectedtotheoppositethalamusbyabandofgraymatter,theinterthalamic connection(interthalamicadhesion)


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Coronalsectionofthecerebralhemispheresshowingthepositionandrelationsofthe

thalamus.

Posteriorviewofthebrainstemshowingthethalamusandthetectum ofthemidbrain.


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SubdivisionsoftheThalamus

Coverings superiorsurface:thinlayerofwhitemattercalledthestratumzonale

lateralsurface:externalmedullarylamina

Internalmedullarylamina dividesthalamusintomedialandlateralhalves

consistsofnervefibersthatpassfromonethalamicnucleustoanother

anterosuperiorly,theinternalmedullarylaminasplits,resemblingaYshape

threemainsubdivisions anteriorpartliesbetweenthelimbsoftheY

medialandlateralpartslieonthesidesofthestemoftheY

eachofthethreepartsofthethalamuscontainsagroupofthalamicnuclei

smallernucleargroupsaresituatedwithintheinternalmedullarylamina,and

some

are

located

on

the

medial

and

lateral

surfaces

of

the

thalamus

Partsof

the

Thalamus AnteriorPart

containstheanteriorthalamicnuclei

receivethemammillothalamic tractfromthemammillarynuclei

alsoreceivereciprocalconnectionswiththecingulategyrus andhypothalamus

functioncloselyassociatedwiththatofthelimbicsystemandisconcernedwithemotionaltoneandthemechanismsofrecentmemory

MedialPart containsthelargedorsomedial nucleusandseveralsmallernuclei

hastwowayconnectionswiththewholeprefrontalcortexofthefrontallobeofthecerebralhemisphere

similarconnectionswiththehypothalamicnuclei

interconnectedwithallothergroupsofthalamicnuclei

responsiblefortheintegrationofalargevarietyofsensoryinformation,includingsomatic,visceral,andolfactoryinformation,andtherelationofthisinformationtoone'semotionalfeelingsandsubjectivestates

LateralPart

subdivided

into

a

dorsal

tier

and

a

ventral

tier DorsalTieroftheNuclei

includesthelateraldorsalnucleus,thelateralposteriornucleus,andthepulvinar

haveinterconnectionswithotherthalamicnucleiandwiththeparietallobe,cingulategyrus,andoccipitalandtemporallobes

VentralTieroftheNuclei consistsofthefollowingnucleiinacraniocaudal sequence:VA,VL,VP


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Threedimensionaldiagramofthethalamus.Majornucleargroupsaredemarcatedbythe

internalmedullarylamina.Midlineconnectionofthalami(interthalamic adhesion)isalso

Illustrated.

Importantthalamocorticalprojections.(Adaptedfrom

anoriginalpaintingbyFrank

H.Netter,M.D.,fromThe

CIBACollectionofMedical

Illustrations,copyrightby

CIBAPharmaceutical

Company,DivisionofCIBA

GEIGYCorporation.)


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OtherNuclei Theintralaminar nuclei

smallcollections

of

nerve

cells

within

the

internal

medullary

lamina

receivefibersfromthereticularformationaswellasfibersfromthespinothalamic andtrigeminothalamic tracts

sendfiberstootherthalamicnuclei,whichinturnprojecttothecerebralcortex,andfiberstothecorpusstriatum

influencethelevelsofconsciousnessandalertnessinanindividual

Themidlinenuclei consistofgroupsofnervecellsadjacenttothethirdventricleandinthe

interthalamic connection

receiveafferentfibersfromthereticularformation.Theirprecisefunctionsareunknown

Thereticularnucleus athinlayerofnervecellssandwichedbetweentheexternalmedullarylamina

andtheposteriorlimboftheinternalcapsule

afferentfibersconvergeonthisnucleusfromthecerebralcortexandthe

reticularformation

outputismainlytootherthalamicnuclei

maybeconcernedwithamechanismbywhichthecerebralcortexregulatesthalamicactivity

Other

Nuclei medialgeniculatebody formspartoftheauditorypathwayandisaswellingontheposteriorsurfaceofthethalamus

beneaththepulvinar

afferentfiberstothemedialgeniculatebodyformtheinferiorbrachiumandcomefromtheinferiorcolliculus

inferiorcolliculus receivestheterminationofthefibersofthelaterallemniscus

receivesauditoryinformationfrombothearsbutpredominantlyfromtheoppositeear

efferentfibersleavethemedialgeniculatebodytoformtheauditoryradiation,whichpassestotheauditorycortexofthesuperiortemporalgyrus

lateralgeniculatebody formspartofthevisualpathwayandisaswellingontheundersurfaceofthepulvinar ofthe

thalamus

consistsofsixlayersofnervecellsandistheterminusofallbutafewfibersoftheoptictract(exceptthefiberspassingtothepretectal nucleus)

fibersaretheaxonsoftheganglioncelllayeroftheretinaandcomefromthetemporalhalfoftheipsilateral eyeandfromthenasalhalfofthecontralateral eye,thelatterfiberscrossingthemidlineintheopticchiasma

eachlateral

geniculate

body,

therefore,

receives

visual

information

from

the

opposite

field

of

vision

efferentfibersleavethelateralgeniculatebodytoformthevisualradiation,whichpassestothevisualcortexoftheoccipitallobe


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Corticalareasofthethalamicprojectionsonthelateralsurfaceofthecerebralhemisphere.

Theseprojectionsarespecificsiteswherecertainsensoryand/ormotorimpulsesare

Integrated.


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ConnectionsoftheThalamus

everythalamicnucleus(exceptthereticularnucleus)sendsaxonstospecificpartsofthecerebralcortex

everypartofthecerebralcortexsendsreciprocalfibersbacktothethalamicnuclei

indicatethatinformationreceivedbythethalamusisalwayssharedwiththecerebralcortexandthatthecortexandthalamuscanmodifyeachother'sactivities

animportantrelaystationfortwosensorymotoraxonalloopsinvolvingthecerebellumandthebasalnuclei thecerebellarrubrothalamiccorticalpontocerebellarloop

thecorticalstriatalpallidalthalamiccorticalloop

botharenecessaryfornormalvoluntarymovement

Mainconnectionsofthethalamus.Afferentfibersareshownontheleft,andefferent

fibersareshownontheright.


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Schematicdiagramofthemedialsurfaceofthebrainillustratingcortical

projectionsofthalamicnuclei

Summaryofthemain

afferentandefferent

connectionsofthethalamic

relaynuclei


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Schematicdrawingoftheafferentand

efferent

connectionsofthelateraldorsalnucleus

Simplifieddiagramofthemainprojections

and

afferentofthelateralposteriorthalamic

nucleus


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Schematicdiagramoftheafferentsofthe

dorsomedial nucleusofthethalamuswhich

contributetotheformationofansa

peduncularis

Schematicdiagramofthe

afferentandefferentfibers

ofthedorsalmedial

nucleusofthethalamus.

Notethattheconnection

tothecorpusstriatumis

bilateral.Theprojections

ofthedorsomedial

nucleustothemammillary

body,tuberoinfundibular

region,andpreoptic area

comprisethe

periventricularsystem


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FunctionoftheThalamus

madeupofcomplicatedcollectionsofnervecellsthatarecentrallyplacedinthebrainandareinterconnected

vastamountofsensoryinformationofalltypes(exceptsmell)convergesonthethalamusandpresumablyisintegratedthroughtheinterconnectionsbetweenthenuclei

informationpatternisdistributedtootherpartsofthecentralnervoussystem

olfactoryinformationisfirstintegratedatalowerlevelwithtasteandothersensationsandisrelayedtothe

thalamusfrom

the

amygdaloid complex

and

hippocampusthroughthemammillothalamic tract

Functionof

the

Thalamus

anatomicallyandfunctionally,thethalamusandthecerebralcortexarecloselylinked

fiberconnectionshavebeenestablished,anditisknownthatfollowingremovalofthecortex,thethalamuscanappreciatecrudesensations

cerebralcortexisrequiredfortheinterpretationofsensationsbasedonpastexperiences ifthesensorycortexisdestroyed,onecanstillappreciatethe

presenceofahotobjectinthehand

however,appreciationoftheshape,weight,andexacttemperatureof

the

object

would

be

impaired thalamuspossessescertainveryimportantnucleiwhose

connectionshavebeenclearlyestablished

includetheventralposteromedialnucleus,theventralposterolateralnucleus,themedialgeniculatebody,andthelateralgeniculatebody


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FunctionoftheThalamus

Theventroanterior andtheventrolateral nucleiofthethalamusformpartofthebasalnucleicircuitandthusareinvolvedintheperformanceofvoluntarymovements.Thesenucleireceiveinputfromtheglobus pallidus andsendfiberstotheprefrontal,supplemental,andpremotorareasofthecerebralcortex.

Thelargedorsomedial nucleushasextensiveconnectionswiththefrontallobecortexandhypothalamus.Thereisconsiderableevidencethatthisnucleusliesonthepathwaythatisconcernedwithsubjectivefeelingstatesandthepersonalityoftheindividual.

Theintralaminar nucleiarecloselyconnectedwiththeactivitiesofthereticularformation,andtheyreceivemuchoftheirinformationfromthissource.Theirstrategicpositionenablesthemtocontrolthelevelofoverallactivityofthecerebralcortex.Theintralaminarnuclei

are

thus

able

to

influence

the

levels

of

consciousness

and

alertnessinanindividual.

Clinicalcorrelations

SensoryLoss usuallyresultfromthrombosisorhemorrhageofoneofthearteriessupplyingthethalamus

damagetotheventralposteromedialnucleusandtheventralposterolateral nucleuswillresultinthelossofallformsofsensation,includinglighttouch,tactilelocalizationanddiscrimination,andmusclejointsensefromtheoppositesideofthebody

thalamiclesionresultsindysfunctionofneighboringstructures,producingsymptomsandsignsthatovershadowthoseproducedbythethalamicdisease

vascularlesionofthethalamusmayalsoinvolvethemidbrain,withresultingcoma,oralateralextensionofthalamicdiseasemayinvolvetheinternalcapsuleandproduceextensivemotorandsensorydeficits

SurgicalReliefofPainbyThalamicCauterization intralaminar nucleiofthethalamusareknowntotakepartintherelayofpaintothecerebral

cortex

cauterizationofthesenucleihasbeenshowntorelievesevereandintractablepainassociatedwithterminalcancer

ThalamicPain thalamicpainmayoccurasthepatientisrecoveringfromathalamicinfarct

spontaneouspain,whichisoftenexcessive(thalamicoverreaction),occursontheoppositesideofthebody

painfulsensationmaybearousedbylighttouchorbycoldandmayfailtorespondtopowerfulanalgesicdrugs


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Clinicalcorrelations

AbnormalInvoluntaryMovements

choreoathetosis withataxiamayfollowvascularlesionsofthethalamus

notcertainwhetherthesesignsinallcasesareduetothelossoffunctionofthethalamusortoinvolvementoftheneighboringcaudateandlentiform nuclei

ataxiamayariseastheresultofthelossofappreciationofmuscleandjointmovementcausedbyathalamiclesion

ThalamicHand contralateralhandisheldinanabnormalpostureinsomepatients

withthalamiclesions

wristispronatedandflexed,themetacarpophalangeal jointsareflexed,andtheinterphalangeal jointsareextended

fingerscan

be

moved

actively,

but

the

movements

are

slow

conditionisduetoalteredmuscletoneinthedifferentmusclegroups

HYPOTHALAMUS


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TheHypothalamus

small(0.3%ofthetotalbrain)

averyimportantpartofthecentralnervoussystem

isessentialforlife

atthecenterofthelimbicsystem

thesiteofnumerousconverginganddivergingneuronalpathways

abletosamplethebloodchemistrythroughitsvascularsupply

hypothalamusmakesappropriatecontrollingresponsesfollowingtheintegrationofitsnervousandchemicalinputs

controlbodyhomeostasis,throughtheautonomicnervoussystemandtheneuroendocrinesystem,andtoplayavitalroleinemotionalbehavior

Sagittalsectionofthebrainshowingthepositionofthe

hypothalamus


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Hypothalamicnucleiandassociatedareas

Hypothalamus Location

posteriortotheopticchiasma

ventraltothethalamus

betweenthethirdventricleandthesubthalamus

connectedventrallytothepituitarygland

dividedintolateralandmedialpartsbythefornix

caudally,thehypothalamusmergesintothetegmentum ofthemidbrain

lateralboundaryofthehypothalamusisformedbytheinternalcapsule

relatedto

the

following

structures,

from

anterior

to

posterior

opticchiasma

tubercinereum andtheinfundibulum

mammillarybodies.


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MedialZone

followinghypothalamicnucleicanberecognized,fromanteriortoposteriorpartofthepreoptic nucleus

anteriornucleus,whichmergeswiththepreopticnucleus

partofthesuprachiasmatic nucleus

paraventricular nucleus

dorsomedial nucleus

ventromedialnucleus

infundibular (arcuate)nucleus

posteriornucleus

LateralZone

followinghypothalamicnucleicanbe

recognized,fromanteriortoposterior

partofthepreoptic nucleus

partofthesuprachiasmatic nucleus

supraoptic nucleus

lateralnucleus

tuberomammillary nucleus

lateraltuberal nuclei.


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Sagittalsectionofthebrain

showingthehypothalamic

nuclei.

A:Medialzonenucleilying

medialtotheplaneofthe

fornixandthe

mammillothalamic tract.

B:Lateralzonenucleilying

lateraltotheplaneofthe

fornixandthe

mammillothalamic tract.

Coronalsectionofthecerebralhemispheresshowingthepositionofthehypothalamic

nuclei.


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LinesofCommunication

hypothalamusreceivesinformationfromthe

restofthebodythrough

nervousconnections

thebloodstream

cerebrospinalfluid

AfferentConnectionsofthe

Hypothalamus

Somaticandvisceralafferents throughcollateralbranchesofthelemniscal afferentfibers

andthetractus solitarius andthroughthereticularformation

Visualafferents leavetheopticchiasma andpasstothesuprachiasmatic

nucleus

Olfactiontravelsthroughthemedialforebrainbundle

Auditoryafferents

havenotbeenidentified

sinceauditorystimulicaninfluencetheactivitiesofthehypothalamus,theymustexist


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AfferentConnectionsofthe

Hypothalamus Corticohypothalamic fibers

arisefromthefrontallobeofthecerebralcortex

passdirectlytothehypothalamus

Hippocampohypothalamic fibers passfromthehippocampusthroughthefornixtothemammillarybody

neurophysiologistsregardthehypothalamusasthemainoutputpathwayofthelimbicsystem

Amygdalohypothalamic fiberspass fromtheamygdaloid complextothehypothalamusthroughthestria

terminalis andbyaroutethatpassesinferiortothelentiform nucleus

Thalamohypothalamic fibers arisefromthedorsomedial andmidlinethalamicnuclei

Tegmentalfibers arise

from

the

midbrain

Sagittalsectionofthebrainshowingthemain

afferentpathwaysenteringthe

hypothalamus.


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Schematicdrawingoftheafferentandefferentfibersofthehypothalamus.Someoftheseconnectionse.g.fromthehippocampalformationarebilateral


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Themammillotegmental tractarisesfromthe

mammillarybodyandterminatesinthecells

ofthereticularformationinthetegmentum of

themidbrain.

Multiplepathwaystothelimbicsystem

Sagittalsectionofthebrainshowingthemainefferentpathwaysleavingthe

hypothalamus.


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Thevariousconnectionsofthehypothalamus.SomeoftheseconnectionsformfeedbackloopssuchasPapez circuitofemotion

ConnectionsoftheHypothalamus

WiththeHypophysis Cerebri

hypothalamusisconnectedtothehypophysiscerebri (pituitarygland)bytwopathways

nervefibersthattravelfromthesupraoptic andparaventricular nucleitotheposteriorlobeofthehypophysis

longandshortportalbloodvesselsthatconnectsinusoidsinthemedianeminenceandinfundibulum

with

capillary

plexuses

in

the

anterior

lobe

of

the

hypophysis

thesepathwaysenablethehypothalamustoinfluencetheactivitiesoftheendocrineglands


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A. Hypothalamohypophyseal tract B.Hypophyseal portalsystem

Hypothalamohypophyseal Tract vasopressinandoxytocinsynthesizedinthenervecells

Supraoptic

Paraventricular nuclei

hormonesarepassedalongtheaxonstogetherwithcarrierproteinscalledneurophysins andarereleasedattheaxonterminals vasopressin(antidiuretichormone)isproducedmainlyinthenervecellsofthesupraoptic

nucleus functionistocausevasoconstriction

antidiureticfunctionincreaseabsorptionofwaterintheDCTandcollectingtubulesofthekidney

Oxytocinproducedmainlyintheparaventricular nucleus Oxytocinstimulatesthecontractionofthesmoothmuscleoftheuterusandcausescontractionofthe

myoepithelial cellsthatsurroundthealveoliandductsofthebreast

endofpregnancy,oxytocinisproducedinlargeamountsandstimulateslaborcontractionsoftheuterus

whenthe

baby

suckles

at

the

breast,

anervous

reflex

from

the

nipple

stimulates

the

hypothalamus

to

producemoreofthehormone

promotescontractionofthemyoepithelial cellsandassistsintheexpressionofthemilkfromthebreasts

supraoptic nucleus,whichproducesvasopressin,actsasanosmoreceptor ifosmoticpressureofthebloodcirculatingthroughthenucleusbetoohigh,thenervecells

increasetheirproductionofvasopressin,andtheantidiureticeffectofthishormonewillincreasethereabsorptionofwaterfromthekidney

theosmoticpressureofthebloodwillreturntonormallimits


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Hypophyseal PortalSystem

Neurosecretory cellssituatedmainlyinthemedialzoneofthehypothalamusareresponsiblefortheproductionofthereleasinghormonesandreleaseinhibitoryhormones

hormonesarepackagedintogranulesandaretransportedalongtheaxonsofthesecellsintothemedianeminenceandinfundibulum

granulesarereleasedbyexocytosisontofenestratedcapillariesattheupperendofthehypophyseal portalsystem

hypophyseal portalsystemisformedoneachsidefromthesuperiorhypophyseal artery,whichisabranchoftheinternalcarotidartery

arteryentersthemedianeminenceanddividesintotuftsofcapillaries

capillariesdrain

into

long

and

short

descending

vessels

that

end

in

theanteriorlobeofthehypophysis bydividingintovascularsinusoidsthatpassbetweenthesecretorycellsoftheanteriorlobe


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Functionsof

the

Hypothalamus

AutonomicControl hypothalamushasacontrollinginfluenceontheautonomicnervoussystem

andappearstointegratetheautonomicandneuroendocrinesystems,thuspreservingbodyhomeostasis

hypothalamusshouldberegardedasahighernervouscenterforthecontroloflowerautonomiccentersinthebrainstemandspinalcord

EndocrineControl nervecellsofthehypothalamicnuclei,byproducingthereleasingfactorsor

releaseinhibitingfactorscontrolthehormoneproductionoftheanteriorlobeofthehypophysis (pituitarygland)

anteriorlobehormonesincludegrowthhormone,prolactin(luteotropichormone),adrenocorticotropichormone,thyroidstimulatinghormone,

luteinizinghormone,

and

follicle

stimulating

hormone

someofthesehormonesactdirectlyonbodytissues,whileothers,suchasadrenocorticotropichormone,actthroughanendocrineorgan,whichinturnproducesadditionalhormonesthatinfluencetheactivitiesofgeneralbodytissues

eachstageiscontrolledbynegativeandpositivefeedbackmechanisms


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FunctionsoftheHypothalamus

Neurosecretion

secretionofvasopressinandoxytocin

TemperatureRegulation anteriorportionofthehypothalamuscontrolsthosemechanismsthat

dissipateheatloss

experimentalstimulationofthisareacausesdilatationofskinbloodvesselsandsweating,whichlowerthebodytemperature

stimulationoftheposteriorportionofthehypothalamusresultsinvasoconstrictionoftheskinbloodvesselsandinhibitionofsweating;therealsomaybeshivering,inwhichtheskeletalmusclesproduceheat

thehypothalamussetsthebodytemperatureat98.0Fto98.6Fwhenmeasuredorallyand1 higherwhenmeasuredrectally

temperatureset

can

be

altered

in

response

to

extremes,

such

as

in

environmentaltemperaturesorininfection

Functionsof

the

Hypothalamus

RegulationofFoodandWaterIntake lateralregionofthehypothalamusinitiatesthefeelingofhungerandresultsinanincreasein

foodintake

lateralregionsometimesisreferredtoasthehungercenter

bilateraldestructionofthiscenterresultsinanorexia,withtheconsequentlossinbodyweight

medialregionofthehypothalamusinhibitseatingandreducesfoodintake

areaisreferredtoasthesatietycenter

bilateraldestructionofthesatietycenterproducesanuncontrolledvoraciousappetite,causingextremeobesity

Experimentalstimulationofotherareasinthelateralregionofthehypothalamuscausesanimmediateincreaseinthedesiretodrinkwater areaisreferredtoasthethirstcenter

supraoptic nucleusofthehypothalamusexertsacarefulcontrolontheosmolarity ofthe

blood

through

the

secretion

of

vasopressin

(antidiuretic

hormone)

by

the

posterior

lobe

of

the

hypophysis

hormonecausesagreatincreaseinthereabsorptionofwaterinthedistalconvolutedtubulesandcollectingtubulesofthekidneys


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FunctionsoftheHypothalamus

EmotionandBehavior functionofthehypothalamus,thelimbicsystem,andtheprefrontalcortex

hypothalamusistheintegratorofafferentinformationreceivedfromotherareasofthenervoussystemandbringsaboutthephysicalexpressionofemotion

canproduceanincreaseintheheartrate,elevatethebloodpressure,causedrynessofthemouth,flushingorpalloroftheskin,andsweating

canoftenproduceamassiveperistalticactivityofthegastrointestinaltract.

lateralhypothalamicnucleistimulationmaycausethesymptomsandsignsofrage,whereaslesionsoftheseareasmayleadtopassivity

stimulationoftheventromedialnucleusmaycausepassivity, whereaslesionsofthisnucleusmayleadtorage

ControlofCircadianRhythms hypothalamuscontrolsmanycircadianrhythms,includingbodytemperature,adrenocorticalactivity,

eosinophilcount,andrenalsecretion

sleepingandwakefulness,althoughdependentontheactivitiesofthethalamus,thelimbicsystem,andthereticularactivatingsystem

lesionsoftheanteriorpartofthehypothalamusseriouslyinterferewiththerhythmofsleepingandwaking

suprachiasmatic nucleus,whichreceivesafferentfibersfromtheretina,appearstoplayanimportantroleincontrollingthebiologicrhythms

nerve

impulses

generated

in

response

to

variations

in

the

intensity

of

light

are

transmitted

via

this

nucleus

toinfluencetheactivitiesofmanyofthehypothalamicnuclei


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Diagramdepictingthehypothalamus asthechiefcenterofthebrainforcontrolling

theinternal

milieu

of

the

body.

ClinicalCorrelations

ObesityandWasting severeobesitycanoccurastheresultofhypothalamiclesions

generallyassociatedwithgenitalhypoplasiaoratrophy

wastinglesscommonthanobesityinhypothalamicdisease

severecachexiaissuggestiveofdamagetothehypophysis (pituitarygland)

SexualDisorders sexualretardationand,rarely,sexualprecocitywithhypothalamiclesions

Afterpubertythepatientwithhypothalamicdiseasemayhaveimpotenceoramenorrhea

HyperthermiaandHypothermia hyperthermiacanfollowlesionsofthehypothalamuscausedbyheadinjuryorfollowingsurgicaloperations

inthe regionofthehypothalamus

patientwithhyperthermiaisotherwisenormalandhasnosignsofmalaise,whichoccurswithpyrexiasecondarytoinfections

hypothermiaalsocanfollowalesionofthehypothalamus.

DiabetesInsipidus resultsfromalesionofthesupraoptic nucleusorfromtheinterruptionofthenervouspathwaytothe

posteriorlobeofthehypophysis

patient

passes

large

volumes

of

urine

of

low

specific

gravity

patientisextremelythirstyanddrinkslargequantitiesoffluids

conditionmustbedistinguishedfromdiabetesmellitus,inwhichthereisglucosuria

DisturbancesofSleep eitherfrequentshortperiodsofsleepduringthewakinghoursorinsomniahasbeenobservedinpatients

withhypothalamiclesions

EmotionalDisorders attacksofunexplainedweepingorlaughter,uncontrollablerage,depressivereactions,andevenmaniacal

outburstsallhavebeenobservedinpatientswithhypothalamiclesions


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Thalamus Hypothalamus [Repaired].pdf