Post on 11-Jan-2016
Brain OrganizationBrain Organization
Psychology 2606Psychology 2606
IntroductionIntroduction
We touched a teeny bit on neurons and We touched a teeny bit on neurons and glial cells last timeglial cells last time
Let’s get into it in detailLet’s get into it in detailNeurons are the basic information Neurons are the basic information
processing unit of the nervous systemprocessing unit of the nervous system It may be the case that single neurons can It may be the case that single neurons can
control behaviour and store informationcontrol behaviour and store informationOther times (perhaps more commonly) Other times (perhaps more commonly)
networks of neurons do thisnetworks of neurons do this
Amazing neuron factsAmazing neuron facts
Impress your friends and be the life of the Impress your friends and be the life of the party with these ice breakersparty with these ice breakers
1) You are born with almost all of your 1) You are born with almost all of your neuronsneurons
2) Neurons change with experience2) Neurons change with experience3) If they do not make connections, they 3) If they do not make connections, they
die!die!4) We CAN grow new ones in the CNS4) We CAN grow new ones in the CNS5) Genetic blueprint can be ‘reopened’5) Genetic blueprint can be ‘reopened’
Some Cell anatomy and physiologySome Cell anatomy and physiology
Axons and dendrites increase the cell’s Axons and dendrites increase the cell’s surface area greatlysurface area greatly
Dendrites are even bigger due to dendritic Dendrites are even bigger due to dendritic spinesspines
Only one axonOnly one axonStarts at the axon hillockStarts at the axon hillockMight be many branches of the axon, Might be many branches of the axon,
these are called teleodendriathese are called teleodendria
Cells have lots of partsCells have lots of parts
Terminal buttonTerminal buttonConnects with next dendriteConnects with next dendrite
Though there is a gap, the synapseThough there is a gap, the synapse Information basically travels down from the Information basically travels down from the
dendrite, through the axon, to the next dendrite, through the axon, to the next dendrite and so ondendrite and so on
Different types of neuronsDifferent types of neurons
Bipolar neuron, short Bipolar neuron, short dendrite, short axondendrite, short axon
Sensory neuron has Sensory neuron has more connectionsmore connections
InterneuronsInterneurons Association (stellate cell)Association (stellate cell) PyramidalPyramidal PurkinjePurkinje
Motor neuronMotor neuron Synapses to a muscleSynapses to a muscle
A little bit about synapsesA little bit about synapses
Recent discoveryRecent discovery (though Sherrington figured it out earlier on)(though Sherrington figured it out earlier on)
Chemical messages (neurotransmitters)Chemical messages (neurotransmitters)Feedback Feedback Excitation and inhibitionExcitation and inhibition
With many connections this is a relatively With many connections this is a relatively complex calculation, and there is a temporal complex calculation, and there is a temporal window and a spatial one too!!window and a spatial one too!!
Glial CellsGlial Cells
Glial cells keep your brain running Glial cells keep your brain running on time…on time…
Well indeed, they serve a repair functionWell indeed, they serve a repair functionSay you get a deep cut, you may get Say you get a deep cut, you may get
paralysisparalysisOld axon diesOld axon diesMicroglia and Schwann cells go into the Microglia and Schwann cells go into the
pathway and sort of clear the way for a pathway and sort of clear the way for a new axonnew axon
Neuron sprouts until it finds the pathNeuron sprouts until it finds the path
Too bad this doesn’t happen in the Too bad this doesn’t happen in the CNSCNS
Glial cells sort of seal off any injuryGlial cells sort of seal off any injuryActually secrete a chemical (NOGO) that Actually secrete a chemical (NOGO) that
stops growth!stops growth!There has been some success with There has been some success with
blocking NOGO, using tubes, using stem blocking NOGO, using tubes, using stem cells etccells etc
ElementsElements HH CC OO NN CaCa PP KK SS NaNa ClCl
Cell anatomyCell anatomy
Genes, cells, Proteins and Genes, cells, Proteins and behaviourbehaviour
‘‘Trying to determine how much of a Trying to determine how much of a behaviour is due to genetics and how behaviour is due to genetics and how much is due to the environment is like much is due to the environment is like trying to determine how much the area of trying to determine how much the area of a field is caused by its length and how a field is caused by its length and how much by its width’much by its width’
Donald HebbDonald HebbNature v. Nurture is a stupid argumentNature v. Nurture is a stupid argument
Key TermsKey Terms
GeneGene GenotypeGenotype PhenotypePhenotype ChromosomeChromosome LocusLocus AlleleAllele DiploidDiploid
HaploidHaploid GameteGamete ZygoteZygote RecessiveRecessive DominantDominant HomozygousHomozygous HeterozygousHeterozygous
Note that it is not the Note that it is not the case that the case that the chromosomes just chromosomes just pair off, there is also pair off, there is also recombinationrecombination
So, each sex cell is a So, each sex cell is a little bit differentlittle bit different
This Recombination is the source of much This Recombination is the source of much
genetic variation, and it occurs in all but genetic variation, and it occurs in all but the simplest organismsthe simplest organisms
Mutation is the ONLY source of new Mutation is the ONLY source of new genetic materialgenetic materialMost mutations are bad, usually lethalMost mutations are bad, usually lethalSome are neutralSome are neutralSome (very few) confer an advantageSome (very few) confer an advantage
A little backgroundA little background
You get half of your genes from your You get half of your genes from your mother and half from your fathermother and half from your father
Single genes can affect a characteristicSingle genes can affect a characteristicMany genes can affect a characteristicMany genes can affect a characteristic It is always an interactionIt is always an interaction
An ExampleAn Example
Human Ocular cutaneous albinismHuman Ocular cutaneous albinism I wonder where that example came from…..I wonder where that example came from…..
Single gene for the production of melaninSingle gene for the production of melaninA – normalA – normala - bada - badDominance / Recessive relationshipDominance / Recessive relationshipAA, aA, Aa all lead to normal, aa leads to AA, aA, Aa all lead to normal, aa leads to
meme
Leslie and RickLeslie and Rick Aa and AaAa and Aa
Or some variationOr some variation aA and AaaA and Aa Aa and aAAa and aA aA and aAaA and aA
Phenotypically normalPhenotypically normal
1 in 4 chance of 1 in 4 chance of having a kid with aahaving a kid with aa
They did, on June 23, They did, on June 23, 19651965
My genotype MUST My genotype MUST be aa because there be aa because there is no dominanceis no dominance
Danny and Stephanie Danny and Stephanie may be carriers, or may be carriers, or they may not be, they they may not be, they are phenotypically are phenotypically normalnormal
Their kids could carry Their kids could carry the allele, assuming the allele, assuming they dothey do
They got the looks, but I got the brains……..
My kids MUST carry My kids MUST carry the allele, as they had the allele, as they had an a from me, and, an an a from me, and, an A from Isabelle A from Isabelle
We know they got an We know they got an A from Isabelle by A from Isabelle by looking at their looking at their phenotypephenotype
Behavioural EffectsBehavioural Effects
I don’t spend much time in the sunI don’t spend much time in the sun I have very poor vision (20/200, melanin I have very poor vision (20/200, melanin
guides the growth of the visual system)guides the growth of the visual system)No binocular visionNo binocular visionCan’t drive a carCan’t drive a carNot very good at baseballNot very good at baseballHuge IQ…….Huge IQ…….
Another cool exampleAnother cool example
Mutant hamstersMutant hamsters Martin RalphMartin Ralph Tau geneTau gene TT normal 24 hr TT normal 24 hr
cyclecycle tt 20 hr cyclett 20 hr cycle Tt or tT gives 22 hr Tt or tT gives 22 hr
cyclecycle
Teenage Mutant Ninja HamstersTeenage Mutant Ninja Hamsters
Single Gene effectSingle Gene effectAffects brain developmentAffects brain developmentSCN specificallySCN specificallyMay be cognitive effectsMay be cognitive effects
Learning Mutants in DrosophilaLearning Mutants in Drosophila
The white rat of The white rat of geneticsgenetics
DunceDunce AmnesiaAmnesia StuckStuck Coitus interruptusCoitus interruptus Bang sensitiveBang sensitive PerPer
This one is cool…This one is cool…
So, What Does it All Mean?So, What Does it All Mean?
What does ‘a gene for behaviour’ mean?What does ‘a gene for behaviour’ mean? Behavioural difference caused by genetic differenceBehavioural difference caused by genetic difference Does not mean that a complex behavioural sequence Does not mean that a complex behavioural sequence
is caused by a single geneis caused by a single gene Many other genes contribute to behaviourMany other genes contribute to behaviour Some difference must be caused by genetic differencesSome difference must be caused by genetic differences
Just because something has a genetic basis Just because something has a genetic basis does not make in unchangeable!!!!does not make in unchangeable!!!!
Remember, Genotype is NOT PhenotypeRemember, Genotype is NOT Phenotype