Transcript Brain Organization

Brain Organization
Psychology 2606
Introduction
We touched a teeny bit on neurons and
glial cells last time
 Let’s get into it in detail
 Neurons are the basic information
processing unit of the nervous system
 It may be the case that single neurons can
control behaviour and store information
 Other times (perhaps more commonly)
networks of neurons do this
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Amazing neuron facts
Impress your friends and be the life of the
party with these ice breakers
 1) You are born with almost all of your
neurons
 2) Neurons change with experience
 3) If they do not make connections, they
die!
 4) We CAN grow new ones in the CNS
 5) Genetic blueprint can be ‘reopened’
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Some Cell anatomy and physiology
Axons and dendrites increase the cell’s
surface area greatly
 Dendrites are even bigger due to dendritic
spines
 Only one axon
 Starts at the axon hillock
 Might be many branches of the axon,
these are called teleodendria
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Cells have lots of parts
Terminal button
 Connects with next dendrite
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Though there is a gap, the synapse
Information basically travels down from the
dendrite, through the axon, to the next
dendrite and so on
Different types of neurons
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Bipolar neuron, short
dendrite, short axon
Sensory neuron has
more connections
Interneurons
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Association (stellate
cell)
Pyramidal
Purkinje
Motor neuron
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Synapses to a muscle
A little bit about synapses
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Recent discovery
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(though Sherrington figured it out earlier on)
Chemical messages (neurotransmitters)
 Feedback
 Excitation and inhibition
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With many connections this is a relatively
complex calculation, and there is a temporal
window and a spatial one too!!
Glial Cells
Glial cells keep your brain running
on time…
Well indeed, they serve a repair function
 Say you get a deep cut, you may get
paralysis
 Old axon dies
 Microglia and Schwann cells go into the
pathway and sort of clear the way for a
new axon
 Neuron sprouts until it finds the path
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Too bad this doesn’t happen in the
CNS
Glial cells sort of seal off any injury
 Actually secrete a chemical (NOGO) that
stops growth!
 There has been some success with
blocking NOGO, using tubes, using stem
cells etc
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Elements
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H
C
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N
Ca
P
K
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Na
Cl
Cell anatomy
Genes, cells, Proteins and
behaviour
‘Trying to determine how much of a
behaviour is due to genetics and how
much is due to the environment is like
trying to determine how much the area of
a field is caused by its length and how
much by its width’
Donald Hebb
 Nature v. Nurture is a stupid argument
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Key Terms
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Gene
Genotype
Phenotype
Chromosome
Locus
Allele
Diploid
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Haploid
Gamete
Zygote
Recessive
Dominant
Homozygous
Heterozygous
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Note that it is not the
case that the
chromosomes just
pair off, there is also
recombination
So, each sex cell is a
little bit different
This Recombination is the source of much
genetic variation, and it occurs in all but
the simplest organisms
 Mutation is the ONLY source of new
genetic material
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Most mutations are bad, usually lethal
 Some are neutral
 Some (very few) confer an advantage
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A little background
You get half of your genes from your
mother and half from your father
 Single genes can affect a characteristic
 Many genes can affect a characteristic
 It is always an interaction
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An Example
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Human Ocular cutaneous albinism
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I wonder where that example came from…..
Single gene for the production of melanin
 A – normal
 a - bad
 Dominance / Recessive relationship
 AA, aA, Aa all lead to normal, aa leads to
me
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Leslie and Rick
Aa and Aa
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Or some variation
aA and Aa
Aa and aA
aA and aA
Phenotypically normal
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1 in 4 chance of
having a kid with aa
They did, on June 23,
1965
My genotype MUST
be aa because there
is no dominance
They got the looks, but I got the brains……..
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Danny and Stephanie
may be carriers, or
they may not be, they
are phenotypically
normal
Their kids could carry
the allele, assuming
they do
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My kids MUST carry
the allele, as they had
an a from me, and, an
A from Isabelle
We know they got an
A from Isabelle by
looking at their
phenotype
Behavioural Effects
I don’t spend much time in the sun
 I have very poor vision (20/200, melanin
guides the growth of the visual system)
 No binocular vision
 Can’t drive a car
 Not very good at baseball
 Huge IQ…….
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Another cool example
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Mutant hamsters
Martin Ralph
Tau gene
TT normal 24 hr
cycle
tt 20 hr cycle
Tt or tT gives 22 hr
cycle
Teenage Mutant Ninja Hamsters
Single Gene effect
 Affects brain development
 SCN specifically
 May be cognitive effects
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Learning Mutants in Drosophila
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The white rat of
genetics
Dunce
Amnesia
Stuck
Coitus interruptus
Bang sensitive
Per
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This one is cool…
So, What Does it All Mean?
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What does ‘a gene for behaviour’ mean?
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Behavioural difference caused by genetic difference
Does not mean that a complex behavioural sequence
is caused by a single gene
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Many other genes contribute to behaviour
Some difference must be caused by genetic differences
Just because something has a genetic basis
does not make in unchangeable!!!!
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Remember, Genotype is NOT Phenotype