Lecture9

SexualDevelopment&Behavior

Cogs17*UCSD

TheHypothalamus

InterfacewithEndocrine(Hormonal)SystemviaPituitary(Master)Gland

HypothalamusandPituitaryGland

HypothalamusproducesReleasingHormones,thatflowviabloodvesselstoAnteriorPituitary

HypothalamusreleasesotherHormonesasNeurotransmitters

viaaxonstoPosteriorPituitary

Pituitary thenreleasestriggeredhormonesintothebloodstreamofthebody

PituitaryGlandsendsmessagestootherglands

Chromosomes

"SexChromosomes"

XY

Androgens (male)&Estrogens (female)Hormones

WeallhaveBOTH

ANDROGENS

Masculine&Feminine

Acomplexsetoffactorsinfluencegender

Includinggenes,neurotransmitters,hormones,andculture

OrganizingEffects

Thedevelopmentofsexualanatomy,includingbraindifferences

PrenatalDevelopment

RoleofgenesinOrganizingEffects- TDF

TDFTestes

DeterminingFactor

FoundonlyonYchromosome

Anenzymethatappearsat~6-8weeks

"Switch"thatactivatesproductionofTestosterone

Inabsence ofsuchTestosterone,developmentwilldefaulttoFemaleform

TDFappearsbetween6th and8th week

Sexualanatomydevelops

by4th month

Meanwhile,brainisalsodeveloping

FetalDevelopmentofInternal Anatomy

"All-purpose"Gonads

FetalDevelopmentofInternal Anatomy

Androgenspresent

DevelopsasMALE

TriggersAnti-MullerianHormone,

fordegenerationofMullerian ducts

"All-purpose"Gonads

FetalDevelopmentofInternal Anatomy

Androgensabsent

Androgenspresent

DevelopsasMALE

DevelopsasFEMALE

Absenceofandrogens>>Wolffian ducts

degenerate

TriggersAnti-MullerianHormone,

fordegenerationofMullerian ducts

"All-purpose"Gonads

FetalDevelopmentofExternal Anatomy

FetalDevelopmentofExternal Anatomy

Androgenspresent

DevelopsasMALE

FetalDevelopmentofExternal Anatomy

Androgensabsent

Androgenspresent

DevelopsasMALE

DevelopsasFEMALE

Turner'sSyndrome

XOMissingsecondsexchromosome

Developasfemale,althoughinfertile

AndrogenInsensitivity

EvenifhaveTDF&produceTestosterone,cellsmaybeinsensitivetoitseffects

Again,bodydevelopsInternallyandexternallyasfemalealthoughnosecondaryhairgrowth

andinfertile

MasculinizingeffectsofexcessiveEstrogens

Astreatmentforrepeatedmiscarriage,pregnantwomenin1950sreceived

excessiveEstrogens

(Stilldonetoday,butwehavebetterknowledgeofproportions

ofhormonesrequired)

Couldresultinmasculinizedfetus(e.g.clitorislikeheadofpenis,

correctablebysurgery)

But,ifitisTestosteronethatnormallyhasmasculinizingeffect,whydidtheseEstrogentreatments

havesuchaneffect???

Howdidmother'sestrogenmasculinizefetus??

TestosteroneandEstrogenVERYsimilar!

But,sincepregnantwomenallhavehighlevelsofestrogens,whyaren’tALLoffspringmales??!?

So,itisactuallyEstrogen thatmasculinizesALLmales!!

Infact,whenTestosteroneenterscells,itisaromatized(converted)

intoEstrogen

Whydoesn'tmother'sestrogensmasculinizeeveryfetus?

Answer:Alpha-Feto Protein

FetusproducesAlpha-Feto ProteintoBINDwithmother'sestrogens

Inmedicaltreatmentdescribedabove,excessiveestrogensadministeredoverwhelmedthissafeguard,partiallymasculinizingfetus

Thisallowsitsownhormonestodetermineitsgender

Post-natalDevelopment

SecondarySexualCharacteristics

Inbothsexes,atadolescence,HypothalamusreleasesGnRH (Gonadatrophin-ReleasingHormones)

ThesecauseAnteriorPituitarytoreleaseGonadotrophins LH&FSH(Leutinizing &FollicleStimulatingHormones)

ThesestimulateTestes inmales

toreleaseTestosterone>>AdultMaleform

ThesestimulateOvaries infemalestoreleaseEstrogens>>AdultFemaleform

EXCEPTAndrogenAndrostenedione (fromAdrenals)requiredforhairgrowthinFemales

Medial-

MPOAincluding"Sexually-DimorphicNucleus"

SDN(StraightDudesNeed)

2.5Xlargerinmales

GenderDifferencesinBrains– HypothalamusinMALES

VMH(VenusMustHave)

Medial-

GenderDifferencesinBrains– HypothalamusinFEMALES

SignificantlylargerinFemalesthaninMales

Areaalsoregulatesfeedingbehavior– esp criticalinfemales"eatingfortwo"

GenderDifferencesinBrains

Ingalhalikar,PNAS2013

Malebrainsoptimizedforintra-(within)-hemispheric

communication

SuggestsMale brainsfacilitateconnectivitybetweenperceptionandcoordinatedaction,Female brainsfacilitatecommunicationbetweenanalyticalandintuitiveprocessingmodes.

Female brainsforinter-(between)-hemispheric

communication.

GenderDifferencesinBrains

INAH3Enlargedportionof

SexuallyDimorphicNucleusofHypothalamusMPOA

LargerinHeterosexualMales,smallerinFemales

ANDinHomosexual Males

IncludinginInfants

ActivatingEffects

Theroleofthenervoussysteminsexual/reproductive

behavior

Medial-

ActivatingEffects

MPOAreleasesGnRH

Testosteronefeedsback toMPOAescalatingarousal

CirculatetoTestes,release

Testosterone

AnteriorPituitaryReleasesLH&FSH

MALESexualBehavior

PleasureCircuits

VTA (VentralTegmentalArea)respondsbyreleasing

Dopamine toNucleusAccumbens

NucleusAccumbens "RewardCenter"– alsoimplicatedinaddiction

BasalGanglia

MPOAalsostimulatesBasalGanglia,whichsignalsSBN (SpinalNucleusoftheBulbocavernosus)

SBNcausesrhythmiccontractionsforejaculation

Medial-

ActivatingEffects:MALE SexualBehavior

Atorgasm,MPOAsignals

Posterior PituitarytoreleaseOxytocin

Causes"refractoryperiod"

duringwhichMalecannotbearoused

Afterejaculation,Anterior Pituitary

releasesProlactin

LimbicSystem

MPOA alsoreciprocatesinteractionwithMedialAmygdalaandotherpartsofLimbicSystem

PlaysaroleinaggressioneffectsofTestosterone

AlsorespondstoPheromones(morebelow)

Cortex alsoplaysaroleinsexinHumans

Learnedassociationscanstimulate,mediatesexualresponse

EspeciallyPrefrontalCortex

ButalsoVisualCortex

Unlikemanysmell-drivenmammals,primatesexualsignals

tendtobevisual

ActivatingEffects

Inparticular,AndrostenedionereleasedbyAdrenals,

getsconvertedinbloodstreamtoTestosterone

LibidoalsoafunctionofAndrogens

FEMALESexualBehavior

ButtheseoriginatefromAdrenalGlands(notfromMPOA)

ThiscirculatingTestosteronethenimpactsonBOTHMPOA andVMH

Medial-

ActivatingEffects

TestosteronecausesMPOAtorelease

GnRH

Estrogens feedbacktoVMH,escalatingarousal

CirculatetoOvaries,release

Estrogens

AnteriorPituitaryReleasesLH&FSH

FEMALESexualBehavior

Fromthere,Femaleresponsemediatedbysimilar paths

VTA (VentralTegmentalArea)respondsbyreleasing

Dopamine toNucleusAccumbens

BasalGangliaBasalGanglia,signalsSBN

(SpinalNucleusoftheBulbocavernosus)

forrhythmiccontractions

LimbicSystem

MedialAmygdalaactivated,

includingresponsetoPheromones

Cortexplaysrolein

learnedresponses

Inaddition,inFemales...

VMHstimulates

Periaquaductal Grey(PAG)areaofMidbrain>>Endorphins

Endorphinsaddtopleasure,&helpprevent(gate)Pain

AtOrgasmPosteriorPituitaryreleases

Oxytocin

BUTUnlikeinMales,

nofollow-upreleaseofProlactin

Altho note: Prolactinstimulatesmilkproductioninpregnant/lactatingfemales

Limbic(Emotional/Motivational)Systemplaysmajorrole

IncludingviaSMELLthroughOlfactoryBulbs

Oneimportantclassofsmells:Pheromones

=Hormonesinsweat,releasedintoairtocommunication

aboutreproductivestate

Inmostmammals,smellcontrolsLimbicResponses

SpecializedVNO(Vomeronasal Organ)detectsPheromones

UnclearifHumans(orprimates)haveaVNO,

butwestillrespondtoPheromones

Triggersmanyimportantreproductive

behaviors

Male:MaleCompetition

Mating

InfantCare

Smellinfogoesdirectlyto

AmygdalaandotherpartsofLimbicSystem

LimbicSystemalsocalled

"Rhinecephalon"(NoseBrain)

Axonspassthroughporesinskull

SynapseontoMitral cells

inOlfactoryBulb

EffectsofPheromonesonHumanmalematingbehavior

X YAftershave

spikedwithmalePheromones

Vs.regular

aftershaveDependentMeasure:Howmanymendidnot gohomealone?

Results:MoreXthanY

EffectsofPheromonesonHumanfemalebehavior

e.g.Subjectshadsweatofanotherfemaledabbedonupperlip,everydayfor8weeks

Thosewhostuckwithprogram,endedupsynchronizingtheirmenstrualcycleswithdonorofsweat

Similareffectseeninfemaleroommates

Inprimates,mayhelpassurereproduceatsimilartimes,tosharechildcare