Unit 2 | Biological approach (Edexcel)

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The biological approach
Key terms and introduction;
Central nervous system ­ This is made up of the brain and spinal cord
Synapse ­ Small junctions between neurons where neurotransmitters are
released and pass from the terminal button of one neuron to the dendrite
of the receiving neuron
Receptor ­ These receive neurotransmitters that have been fired from the terminal button of
another neuron
Neuron ­ These are nerve cells which pass information around the body
Neurotransmitter ­ A chemical substance that is released at the end of a neuron
Genes ­ Segments of a chromosome that allow parents' traits to be passed on to their offspring
Hormones ­ A regulatory substance that is produced in an organism and is transported via the
bloodstream to stimulate specific cells / tissues into action
Brain lateralisation ­ The fact that the brain is split into two hemispheres; left and right
The biological approach combines biology and psychology to explain human behaviour. This approach
is founded on two assumptions: that our behaviour is the result of the genes that we posses from
contraception; and that our behaviour is controlled by our central nervous system.
Twin and adoption studies;
Twin studies;
This is used to show whether behaviour is shared by those who are genetically identical
Psychologists look at concordance rates to determine how likely it is that twins share traits
(e.g. the likelihood that if one twin develops schizophrenia the other one will too)
Psychologists carry out tests on a large scale to determine the likelihood (e.g. looking at
whether both twins develop the same disorder)
A high concordance rate shows that the trait is probably genetic
Psychologists try to study twins who have not shared the same upbringing to rule out
environmental factors
Adoption studies;
Studying adopted children to see if behaviour traits can be attributed to genetic factors or
Adopted children share no common genes with the adopted parents, but they share the
same environment. They share 50% of their genes with each of their biological parents, but
don't share the same environment
This allows psychologists to separate genetic factors and environmental factors in children
who have been adopted at a very young age by looking for similarities between the children
and their adoptive parents and similarities between the children and their biological parents
If the child has traits that are shared with the biological parents but not with the adoptive
parents then this supports the idea that traits can be attributed to genes.
E.g. If a child and biological mother share a common high IQ, but the adoptive
parents' IQ is low then this can be attributed to genetic factors (e.g. a genius

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Both methods isolate genetic and environmental factors as they study people who share a
biological link, but not a common environment
Studying MZ (identical) twins is the best way to do this because the two participants share
identical genes, but a different environment ­ so similarities in behaviour due to
environmental similarities can be ruled out
MZ twins shared the same pre-natal environment so this could cause some similarities in
behaviour due to environment
Adopted children also shared a pre-natal environment with their mother.…read more

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This produces a 3D `working model' of the brain and can be used to show any malfunctions (such as
The patient is injected with a mixture of water and glucose which incorporates a radioactive isotope
that emits + radiation. It has a half life of around 109 minutes so it doesn't stay in the body too long.
The patient has to wait for the tracer to circulate around the body, and reach the brain before being
scanned ­ usually around 1 hour.…read more

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Animals in labs;
95% are rodents and birds (e.g.…read more

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Studying functions of the brain;
Legion studies (damaging parts of the brain)
Ablation studies (removing parts of the brain)
Testing the effects of antipsychotic drugs on the brain
Research into the effects of physical activity on the brain (e.g. it was found, through animal studies,
that more exercise improves the plasticity of the brain)
Studying the effects of sleep deprivation
Studying genes;
This is possible because of animals' short life span and quick breeding.
Gene therapy is used (genes are altered or implanted)
e.g.…read more

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These studies are also helpful to the species being studied as we learn more about how we
can improve their care
Ethical disadvantages;
Animals are likely to be confined more than they normally would (in the `wild') when they are
in a laboratory setting which is unethical because they are either in an unfamiliar environment
or bred specifically for the purpose of being tested on
Surgical procedures, which could cause pain to the animal, are used.…read more

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The brain contains billions of neurons which pass information around inside the brain and around the
body; telling different parts of the body what to do.
Neurons communicate with each other through synapses ­ passing neurotransmitters from the
terminal button of one, to the dendrite of the next.
Some synapses are excitatory ­ encouraging the neuron to fire
Others are inhibitory ­ telling the neuron not to fire.
Whether or not a neuron fires depends on the amount of excitatory synapses and inhibitory
synapses.…read more


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