Upload
doandan
View
220
Download
2
Embed Size (px)
Citation preview
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)