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