CONSCIOUSNESS,THEBRAINANDBEHAVIOR

PhysiologyUnit2

InPhysiologyToday

WhattheBrainDoes

• Thenervoussystemdeterminesstatesofconsciousnessandproducescomplexbehaviors

• Anygivenneuronmayhaveasmanyas200,000synapseswithotherneurons

• Brainactivity– Statesofconsciousness– Consciousexperiences– Motivationandemotion– Learningandmemory– Spatialawarenessandlanguage

StatesofConsciousness

• Statesofconsciousness

– Thewakingstate– Drowsy– Sleep– Coma– Braindeath

• Consciousexperiences– Thoughts– Feelings– Perceptions– Ideas– Dreams– Reasoning

Consciousness includes 2 distinct concepts

StatesofConsciousness

• Defined2ways1. Bybehavior

– Maximumattentivenesstocoma2. Measuredbypatternofbrainactivity

– Electricalactivityofneuronsinthebrainrecorded– Electroencephalogram(EEG)

EEG

• Electricalactivityofcorticalneuronsismeasuredbyelectrodesplacedonthescalp– Electricalpotentialdifferencesbetweendifferentpointsonthescalp

– EEGpatternsaremostlyduetogradedpotentials• Summedpostsynapticpotentials• Activityfromhundredstothousandsofneuronsjustbelowtheelectrode

EEG

• Themajorityoftheactivityismeasuredfrompyramidalcellsofthecortex

• Recordspostsynapticpotentialsfromthedendrites

Pyramidal cells use glutamate as their excitatory NT and

GABA as their inhibitory NT

EEG

• Amplitude– MeasuredasμV

• Range0.5– 100μV

– Highamplitude• manyneuronsareactivatedsimultaneously

• Synchronousfiring

– Lowamplitude• Fewerneuronsareactivated

• Asynchronousfiring

• Frequency– MeasuredinHz

• Cyclespersecond• Range1-40Hz

– Lowerfrequency• Lessresponsivestates• Sleep

– Higherfrequency• Increasedalertness

EEG

• TypicalEEG• Recordedfromtheparietaloroccipitallobe• Awake,relaxedperson• 4secondsofactivity• Durationofasinglewave50msec

TheWakingState

• Alpharhythm– MostprominentEEGwavepatternofanawake,relaxedadultwhoseeyesareclosed

– Decreasedlevelsofattention

– Subjectfeelsrelaxedandhappy

TheWakingState

• Betarhythm– Attentivetoanoutsidestimulus

– Thinkingaboutsomething

– Lowamplitude,higherfrequency

Sleep

• EEGwavepatternschangeduringsleep• Becomingdrowsy

– Decreaseinalpha-waveamplitudeandfrequency

• Asleep– Slowerfrequencyhigheramplitudewavepatterns– Thetarhythms– Deltarhythms– Changesin

• Posture• Easeofarousal• Motoroutput• Thresholdforsensorystimuli

Sleep

NREM• Nonrapideyemovement

behindaclosedeyelid• Slowwavesleep

– Wavesarehighamplitude,lowfrequency

• 4stages– Eachstageischaracterizedby

anEEGpatternwithaslowerfrequencyandhigheramplitudethantheprecedingone

REM• Rapideyemovement

behindaclosedeyelid• Paradoxicalsleep

– SleeperisdifficulttoarousedespitehavingEEGcharacteristicsoftheawake,alertstate

• Dreamingoccurs

NREMSleep

• Progressionfromstage1-4

• Processreversesitself• Insteadofwakingup,moveintoREMsleep

NREMSleep

• Sleepcontinuesinthecyclicalpattern,ifuninterrupted– 1,2,3,4then4,3,2,1episodeofREMsleepthenrepeats

– Lasts90-100minutes

• Averagetotalnightssleepcomprises4-5cycles

Purple bars are periods of REM sleep

NREMSleep

• Asapersonmovesfromdrowsinesstostage1sleep– Musclesbecomemorerelaxedassleepprogresses

• Exceptocularandrespiratorymuscles• Pulsatilereleasefromanteriorpituitary

– Growthhormone– Gonadotropins(FSH,LH)

• Decreaseinbloodpressure,heartrate,respiratoryrate

REMSleep

• REMsleepis20-25%ofayoungadultstotalsleeptime– Declineswithage

• DurationofREMsleepincreasestowardtheendofanundisturbednight

• Characterizedbyincreaseandirregularity– Bloodpressure– Heartrate– Respiratoryrate

• Muscletwitchesmayoccur(faceandlimbs)

WhyDoWeSleep

• Ahomeostaticrequirement• Importanceofsleep

– Learningandmemory– Brainexperiencesreactivationofneuralpathwaysstimulatedduringthepriorawakestate

– Dampensoverallneuralactivitywhich,inturn,strengthenssynapsesinpathwaysinvolvedinlearningandmemory

LackofSleep

• Impairsimmunefunction• Causescognitivedeficits

– Intellect• Reasoning• Perception• Intelligence• Learning

• Lesseffectivememoryretention

CircadianRhythms

• Circadianrhythmsareanaverageof8hoursofsleepand16hoursawake

• Hypothalamusandthebrainstemdrivecyclicalchanges

• Neuronsofbrainstemgiverisetoaxonsthatbranchtosynapsewithwideareasofthebrain– Calledthereticularactivatingsystem(RAS)

CircadianRhythms• Alternatingreciprocal

activityofdifferentRASneuronscauseshiftsfromonestatetoanother

• Thewakingstate– NeuronsthatreleaseNEand

Serotonindominate

• Sleep– NREM

• IntermediateactivityofNE,SerotoninandACh

– REM• Cholinergicneuronsaredominant

>30NTshavebeenidentifiedthataffect

sleep

HypothalamusControlofCircadianRhythms

• Preopticarea– GABAergicneurons– Promotesslowwavesleep

(NREM3-4)– Inhibitscenterin

hypothalamusthatstimulateswakefulness

• Inhibitshistamine

• Suprachiasmaticnucleus– Stimulatestheproductionof

melatonin bythepinealgland– Timingofsleep/wakecycles

relativetoperiodsoflight/dark

Motivation

• Primarymotivatedbehavior– Relatedtohomeostasis– Bodyneedsaresatisfied– Example:gettingadrinkofwaterwhenyouarethirsty

• Secondarymotivatedbehavior– Notallmotivatedbehaviorrelatestohomeostasis– Decidingwhattypeofsodatodrink– Influencedbyincentives(cravings,habit,learning,intellectandemotions)

Emotion

• Physiologicalbasisofemotion– Emotionalbehavior

• Thehormonal,autonomicandoutwardexpressionsanddisplaysofresponsetothestimulus

– Inneremotions• Theconsciousexperiencesuchasfeelingsoflove,fear,anger,joy,anxiety,hope,etc.

Emotion

• Emotionalbehavior– Limbicsystem– Cerebralcortex

• Amygdalaandassociationcortexarecentraltomostemotionalstates

Learning

• Learning– Acquisitionandstorageofinformation– Rewardsandpunishmentscrucialtolearning

• Memory– Relativelypermanentstorageoflearnedinformation

– Brainprocesses,storesandretrievesinformationindifferentwaystosuitdifferentneeds

Memory• Memoryencoding

– Thephysiologicaleventsthatleadtomemoryformation

• Declarativememory– Retentionandrecallof

consciousexperiencesthatcanbeputintowords

• Proceduralmemory– Memoryofhowtodothings– Learnedemotionalresponses

(fear,Pavlov’sdog)

Memory

• Short-termmemory– Registersandretainsinformationfromsecondstominutesafteritsinput

– Workingmemory

• Long-termmemory– Storedfordaystoyearsandrecalledatalatertime– Consolidation istheconversionofshort-termtolong-termmemory

– Focusingattentionisessentialformemory-basedskills– Thelongerthespanofattentioninworkingmemory,thebettertheabilitytodothings(practicemakesperfect)

Memory• Long-termpotentiation

– Certainsynapsesundergoalong-lastingincreaseintheireffectivenesswhentheyareheavilyused

– Highfrequencyactionpotentials

– Stimulatesthepost-synapticneuronforalongeramountoftime

– BothAMPAandNMDAreceptorsactivatedsimultaneously

Memory

• Hormones,consequencesofourexperiencesaffectourmemoriesofthem– Hormonesnormallyreleasedinstressfulormildlystimulatingexperiences

– Opioidpeptidesinterferewithlearningandmemorywhenthelessoninvolvespain

• Inhibitlearningbydecreasingtheemotionalcomponentofthelearningexperience(fear,anxiety)

• Decreasethemotivationnecessaryforlearning

CerebralDominance

Eachhemisphereofthebrainhasanatomical,chemical,functionalspecializations

LeftBrain,RightBrain

• LeftHemisphere– Theleftbrainisthelogicalbrainresponsibleforwords,logic,numbers,

analysis,lists,linearityandsequence.Itcontrolstherightsideofyourbody.

• RightHemisphere– Therightbrainisthecreativebrainandisresponsibleforrhythm,

spatialawareness,color,imagination,daydreaming,holisticawarenessanddimension.Itcontrolstheleftsideofyourbody.

• CorpusCallosum– Thecorpuscallosumisathickbandofnervefiberswhichconnectthe

braincellsinonehemispheretothoseintheotherhemisphere.Thetwohemisphereskeepupacontinuousconversationviathisneuralbridge.

Malevs.FemaleBrain• FemaleBrain:largerregions

– partsofthefrontallobe• problem-solvinganddecision-making

– Limbicsystemstructure• regulatingemotions

– Whitematter

• MaleBrain:largerregions– Parietalcortex,whichis

involvedin• spaceperception

– Amygdala• sexualandsocialbehavior

– Graymatter

Language

• Acomplexcodethatinvolves– Listening– Seeing– Reading– Speaking

• Centersforlanguagefunctioninthelefthemisphere• Cerebellumimportantinspeakingandwriting

– Involvecoordinatedmusclecontractions

• Malesandfemalesusedifferentareasforlanguageandprocessing(differentstrategies)