Sam
Topic 1 Genes and evolution
What is psychology: Psychology is the scientific study of mind and brain to explain behavior.
Why do we need a science for that? because common sense fails
The genetic basis
Is it correct to claim that “a violent person has violent genes”?
- In the seventies they thought no! environment was the determining factor in the
nineties they thought yes! genes was the determining factor today we know that
genes and the environment interact with each other and determine (violent) behavior .
Behavior is limited by genes but within those limits environment determines how you
will become
Genes: The units of heredity that help determine an organism’s characteristics by providing the cell’s
instructions for making certain proteins
Gene expression: whether a gene is turned “on” or “off”; the extent to which a gene is transcribed
into a sequence of amino acids (protein)
Genotype: an organism’s specific set of genes doesn’t change
Phenotype: Observable physical characteristics and behaviors of an organism is determined by
genotype x environment (experience, past and present) always changes
Behavior genetics: even though two people can have the same genotype , they most likely become
different due different environments (so different phenotype) like identical twins
Heredity: Transmission of characteristics from parents to offspring through genes
Mom (46) x Dad (46) Egg (23) x Sperm (23) baby (46)
- 46 cells are in 23 pairs (chromosones), whereas one of the pair is from the mother and
the other from the father
- The pairs are located at corresponding positions on pairs of chromosomes.
- Allele: one specific variant of a gene, can be dominant or recessive
Homozygote: inherited alleles are the same from both parents
Heterozygote: inherited alleles are different from parents
- Determine e.g. the color of the eyes (brown is dominant, the dominant allele will
always be expressed when present, Homozygote genes of blue eyes necessary to
get blue eyes so two blue recessive genes)
A specific trait or behavior is determined by the interaction between the environment (and...
one gene pair/ multiple gene pairs: polygenetic inheritance (bv with certain minds diseases)
Genome: blueprint for human body where the nose will form etc, is shaped by evolution over the
years
So each cell contains 23 chromosones (pairs of cells, one from mother one from father), each
chromosome contains DNA strands (helix type of shape), and each segment of the DNA strand
consist of individual genes (which instructs the DNA to make certain proteins), but the biochemical
environment inside the cell determine whether the genes are turned of and on and when this
happens, this is important for which proteins are produced and when they are produced (therefore
the genes look different in different body parts, some are turned on in one body part but off at the
other). The biochemical environment inside the cell are influenced by the environment outside the
cell, timing of development, experience, behavior etc.
- Thus: Genes x Environment which genes are turned on or off determines how a cell
looks like how a certain body part looks like behavior
Evolution by natural selection
, Charles Darwin hypothesized that all modern organisms are descended from a small set of
shared ancestors and have merged over time through the process of evolution.
The key mechanism of evolution is natural selection Three conditions:
- There is variation among individuals of a populations
- Individuals with a certain trait survive and reproduce at higher rates than others
- The trait associated with this advantage is passed from parents to offspring
These Specific traits will be better represented in the next generation.
Organisms differ in genotype and variations in genotype are passed from generation to
generation What matters is the survival of genes, not the survival of individuals.
The evidence for modern evolutionary theory comes from many sources:
- the fossil record
- the resemblance between genomes of various organisms (apes 24 with humans 23)
two separate apes chromosomes have merged in one in evolution, explains the
difference
- pseudogenes capable in making vitamin C from glucose, but we lack the final step for
the process (due to a mutation) probably because there were plenty of fruits carrying
vitamin C.
- distribution and difference of species across the world (continental vs oceanic islands)
It does not follow that evolution somehow improves organisms and that it can only lead to
rigid behavioral patterns (they just become better adapted, but the environments keep
changing)
critic Intelligent Design movement: life on earth has been created by an Intelligent
Designer
Genes and behavior
Nature (genes) versus Nurture (environment)
- The nature nurture debate has become increasingly irrelevant there is a continuous
interaction between genes and environment! behavior is the product of both
- Who we are is determined by how our genes are expressed in specific environments
How do the mind and the brain relate?
Answer: The mind (mental activity) is produced by biochemical processes in the brain.'
Topic 2 The brain and the nervous system
Communication of the brain with the body Nervous system:
, Central nervous system:
- Brain
- Spinal cord
Peripheral nervous system:
- Somatic nervous system involved in voluntary behavior e.g. reach for a object
- Autonomic nervous system responsible for the less voluntary behavior e.g. controlling
you heart rate
Sympathetic nervous system prepares the body for action e.g. increases
heart rate
Para-sympathetic nervous system returns the body to a resting state e.g.
slows the heart rate
Endocrine System: release hormones have effect on a large part of the body (longer distances)
Building blocks of the nervous system:
The nervous system is made up of two basic kinds of cells: Glia (supportive function) and
Neurons (important for behavior; ability to transmit signal walk, talk ect)
Different types of neurons:
Sensory receptors (in skin) provide information from the skin and muscles
Sensory (afferent) neurons) carry information from the physical world to the brain
Interneurons (neurons in-between) facilitate communication between sensory and motor
neurons
Motor (efferent) neurons direct muscles to contract and relax
all work together to control movement (e.g. with writing)
Communication among neurons:
Dendrites: : detect signals from neighboring neurons
and send them out
Cell body: the information received via the dendrites is
collected and integrated
Axon: long but small outgrowth of a neuron that
transmits information between the cell body to the
terminal buttons
Terminal button: at the end of a axon, releases
signals from the neuron into the synapse
Membrane: the outer surface of a neuron
Is selectively permeable (some substances move in or out of the membrane, and some do
not)
, Ion channels are located on the mebrane allow ions to pass in and out of the cell when
the neuron transmits signals down the axon ions are electrically charged
By controlling the movement of ions, the membrane plays an important role in
communication between neurons
Inside is mostly negatively charged and the outside positive
Action potential (neural firing): the electric signal that passes along the axon (one-way direction)
causes the terminal buttons to release chemicals into the synapse that transmit signals to other
neurons
When a neuron is resting, the electrical charge inside the neuron is slightly more negative
than the electrical charge outside typically -70 millivolts (= this difference is called resting
membrane potential)
Polarized neuron: more negative than positive ions inside
Two type of ions: sodium and potassium
Ions pass through the neuron membrane at the ion channels. Each channel matches a
specific type of ion: Sodium channels allow sodium ions but not potassium ions to pass
through the membrane, and potassium
channels the other way around. The
flow of ions through each channel is
controlled by a gating mechanism (can
be open and closed).
voltage meter
Changes in electrical potential due to
receiving signals from nearby neurons
lead to an action potential
As the cell fires, it allows more positive
ions inside, when reach +40 the
“doors” closes and then the positive ions are pumped out and it goes in absolute refractory
periode(period in which it cannot open again), then goes to relative refractory period (it
takes more to fire it again) and then back to the resting state.
- As soon as -55 passed than an action potential has been generated firing of a neuron
(could be a thought, muscle contraction ect)
All‐or‐none law: Neurons either fire or do not fire (same potency each time) the
frequency in firing can vary
Neurons interact via synapses through chemical substances (neurotransmitters).
- Synapse: the place where a signal passes from the terminal buttons of a “sending”
neuron and the dendrites of a “receiving” neuron
Presynaptic neuron: the neuron that sends the signal (image purple)
Post synaptic neuron: the neuron that receives the signal (image
green) There are many neurons that effect the post synaptic neuron
Neurotransmitters: Chemical substances that transmit signals from
one neuron to another Lock‐and‐key Model (can bind only with its
particular type of receptor) divides the different signals to know
what each signal is
Located In the terminal button of the presynaptic neuron and
are activated when the action potential is activated
Process is stopped by auto-receptors (ends the release),
synaptic reuptake (the process whereby a neurotransmitter is taken back into the
, presynaptic terminal buttons, thereby stopping its activity) and enzymes (cleans up the
substance)
The binding of a neurotransmitter with a receptor produces an excitatory or inhibitory signal.
Inhibitory: increase polarization by increasing the
negative charge inside the cell relative to outside
the cell and therefor it is harder to pass -55 (goes
more minus than -55 Neuron less likely to fire
Excitatory: depolorize the cell membrane by
decreasing the negative charge inside relative to
the outside of the cell increases the likelihood
that a neuron will fire
Drugs :
Agonists: enhances the action of a neurotransmitter
- Helps produce the neurotransmitter (a precursors) increases the amount of
neurotransmitters made and released by the presynaptic neuron (e.g. drug for Parkinson)
- counteracting the cleanup enzymes and blocking the re ‐uptake
- mimicking the transmitter’s action (increases the impact)
Antagonists:
- reduces the amount of neurotransmitter (precursor) made and released into the synapse
- increase effectiveness cleanup enzymes and enhance the re ‐uptake
- blocking the postsynaptic receptors (prevent the neurotransmitter from activating: does not
fit the lock)
Studying the brain
19th century Phrenology
- Bumps on the skull were interpreted in terms of personality traits (not true ofcourse)
Methods for studying the brain:
Clinical observation of patients with brain damage (brain damage on the back side – trouble
with eye sight; front – planning/thinking)
Experimental techniques:
- Invasive: animal studies (e.g., lesions, single ‐cell recordings)
- TMS (Transcranial Magnetic Stimulation) series of magnetic pulses that disable certain
brain areas for a short time see which areas are necessary for specific psychological
functions
Other techniques:
Electrophysiology (EEG) measure the brain’s electrical activity (big moment!)
Brain imaging
- (f)MRI scan (measure blood flow by looking at changes in the blood’s oxygen level in the
brain
- PET scan (where anabolic activity occurs, see on an image which parts, due to radioactive
glucose that has been injected)
How do PET and fMRI differ from EEG in terms of the brain activity they measure?
Answer: EEG provides information on when a brain response occurs. By contrast, fMRI and PET
provide information about where a response occurs.
