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Introduction to Psychology Notes (VU)
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Lecture 1: Genes and EvolutionIntroduction
Psychology is the scientific study of mind, brain and behaviour.
Psychology is the scientific study of mind and brain to explain behaviour.
● Mind = mental activity, including memories, thoughts, feelings & perceptual experiences (
sights, smells, tastes, sounds & touches ). Mental activity results from biochemical
processes in the brain.
● Behaviour = observable human/animal actions, ranging from subtle to complex. Some are
exclusively human ( e.g. debating philosophy, performing surgery ), some occur in all, such
as eating/drinking.
The Genetic Basis
Is it correct to claim that “a violent person has violent genes”?
In the 70s’s, it was believed to be due to the environment.
In the 90’s it was believed to be due to genes.
Nowadays, it is believed to be a combination of genes + the environment that lead to violent behaviour.
Genes are meaningful sections of a DNA molecule that gives the cell’s functioning by providing
instructions for making proteins.
Gene Expression is whether a gene is turned “on” or “off”. It’s the extent to which a gene is transcribed
into a sequence of amino acids.
In each cell, some genes are expressed at any point in time and others are not. This is controlled by the
biochemical environment inside the cell.
● The biochemical environment is influenced by: the environment outside the cell, timing in
development, overall environment, experience, behaviour.
Genotype is an organism’s specific set of genes
Phenotype is the overt traits and behaviours of an organism. It is determined by genotype + environment (
experience, past & present ).
● e.g. monozygotic twins have the same genotype but different environments.
, In nearly every cell, there are 23 pairs of
chromosomes, made of
deoxyribonucleic acid ( DNA ),
consisting of two strands of molecules in
a double helix shape. Each gene has the
exact instructions to manufacture a
distinct polypeptide.
Each gene is paired with another gene,
and these pairs are located at
corresponding pairs of chromosomes.
Allele is one specific variant of a gene.
● Homozygote means that the two alleles received from the parents are the same.
● Heterozygote means that the two alleles received from the parents are different.
A specific trait or behaviour is determined by the interaction between the environment + one gene
pair/multiple gene pairs ( polygenic inheritance ).
Evolution by Natural Selection
The genome is shaped by evolution over the years — Darwin’s Evolutionary Theory.
He hypothesised that all modern organisms…
● are descended from a small set of shared ancestors.
● have merged over time through the process of evolution.
The key mechanism of evolution is natural selection. There are three conditions for this:
1. There is variation among individuals of a population.
2. Individuals with a certain trait survive and reproduce at higher rates than others.
3. The trait associated with this advantage is passed from parents to offspring.
Specific traits will be better represented in the generation that comes after.
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 the modern Evolutionary Theory comes from many sources:
● The fossil record.
, ● The resemblance between genomes of various organisms.
● Pseudogenes.
● The distribution of species across the world.
● continental islands vs oceanic islands.
However, despite overwhelming evidence, many remain sceptical about the theory of evolution.
Gene Heredity
Selective breeding of flowers led to the first clues to the mechanisms responsible for heredity. It showed
that plants contained separate genes that existed in different versions ( e.g. white or purple ) and that
when determining an offspring’s appearance, some genes were dominant and others were recessive.
A dominant gene from either parent will be expressed if present, and a recessive gene is only expressed
when matched with a similar gene from another parent.
Genetics ( nature ) is one of two influences on phenotype — e.g. two purple flowers have the same
phenotype, but can have different genotypes. Environment ( nurture ) is the second influence — humans
inherit height and skin colour, but good nutrition can increase size, and sunlight can change skin colour.
Genes and Behaviour
The Nature vs Nurture debate has become increasingly irrelevant. Instead, there is a continuous
interaction between genes and the environment.
Who we are is determined by how our genes are expressed in distinct environments.
Going back to the violent person – violent genes debate:
Genes – Environment – Criminal Behaviour
MAOA allele for low MAO activity – Severe Maltreatment – Higher probability of being convicted of
Violent Crimes.
, Lecture 2: The Brain & the Nervous System
Introduction
The interaction between your genes and your environment lead to your phenotype — gene expression.
This goes for the nervous system too, which is the basis for behaviour.
Building Blocks of the Nervous System
The nervous system is made up of two basic kinds of cells: glia & neurons.
Neurons:
They consist of Dendrites, the Nucleus, the Cell Body, the Axon and the
Terminal Buttons that have the Synapses + Membrane.
There are 4 main types:
● Sensory Receptors: specialised cells that
● Sensory ( Afferent ) Neurons: carry information back to the CNS.
● Motor ( Efferent ) Neurons
● Interneurons
Communication Among Neurons
The membrane is semipermeable, which means it selectively allows substances
in or out.
There is a difference in charge between the inside of the cell and the outside of the cell — the difference
between positively or negatively charged ions. At rest, the charge is -70millivolts, meaning it is
negatively charged.
When the membrane opens, meaning the inside can become less negatively charged compared to the
outside, increasing the chances of an action potential.
● Action Potential: temporarily, the inside is more positively charged compared to the
outside of the cell ( reaches +40millivolts ). They happen when a neuron fires.
When an action potential happens, the
sodium channels open and positively
charged sodium ( Na ) ions rush in (
depolarization ).
This changes the charge inside from negative
to positive compared to the outside. Once the
sodium channels close, potassium ( K ) ions
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