thalamus hypothalamus [repaired].pdf
TRANSCRIPT
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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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