Download The biological Approach

The biological
Approach
Core assumptions
The biological approach suggests that everything psychological is
a first biological, so to full understand human behaviour we must
look to biological structures and processes within the body, such
as:
1.
2.
3.
Genetics
The central nervous system, which comprises the brain and
spinal cord
The chemistry of the body
The influence of genes on behaviour
Watch this video on the difference between genotypes and
phenotypes: https://www.youtube.com/watch?v=gLxiqbl4J4
Genotype
• The genotype is an individual’s genetic make-up, which
occurs at conception and provides the genetic code for
how that individual will develop.
• It dictates characteristics such as eye and hair colour.
• Each individual (apart from identical twins) has a genotype
which is unique to them.
Phenotype
• This is the way that genes are expressed through physical,
behavioural and psychological characteristics.
• The expression of a genotype is inevitably influenced by
environmental factors.
• For example, the maximum height of an individual is
dictated by the genotype but environmental factors such
as nutrition will affect how likely the person is to achieve
their potential height.
• This also relates to psychological characteristics- there may
be a genetic predisposition to a behaviour (depression) but
it may not express itself due to the environment stopping
its development.
Genetic basis of behaviour
• To study whether behavioural characteristics, such as intelligence or
mental disorders are inherited often twin studies are conducted.
Monozygotic Twins (Identical)
100% genetically similar
Dizygotic Twins (Non-identical)
Share 50% of genetics
• Twin studies are used to determine the likelihood that certain traits
have a genetic basis by comparing the extent to which both twins
share the same characteristic.
• This is known as the concordance rate.
• If MZ twins show a higher likelihood of sharing
behaviours/disorders than DZ twins then there is argued to be a
genetic component.
• For example:
Disorder
Research
Concordance rate
for MZ twins
Concordance rate
for DZ twins
schizophrenia
Gottesman (1991)
48%
17%
If you are still unclear- this short video will help explain the information
on these slides: https://www.youtube.com/watch?v=Trc2dJgeyvc
Something to think about……
Notice that in the previous table the concordance rates for
schizophrenia in MZ twins is not 100%.
This suggests that although there may be a genetic influence, it is not
the sole reason for the disorder occurring.
If it was entirely due to genetics you would expect the concordance
rates for identical twins to be 100% as they share 100% of their
genetics.
It seems some behaviours could be a mix of both genetics and
environment.
Evolution and behaviour
Evolution= the changes in inherited characteristics in a
biological population over successive generations.
Darwin proposed the theory of natural selection
He suggested that any genetically determined behaviour that
enhances an individual’s survival (and reproduction) will
continue in future generations, i.e. be naturally selected.
The selection occurs because the trait gives the possessor
certain advantages- it becomes adaptive.
The possessor is more likely to survive, reproduce and pass on
the adaptive genes. Thus, the trait remains in the gene pool.
Evolution example
• In simple terms, being aggressive will,
at some point in our ancestry, have been advantageous in terms of
survival and increased chances of reproduction.
• This was perhaps due to gaining resources and protection of
family.
• This is turn increased attractiveness to potential mates.
• This made the likelihood of passing the gene on much greater as
there would be more available mates.
• The genetics could then have been passed on to subsequent
generations and the behaviour became more widespread
(aggression remains in the gene pool)
• This video explains more:
https://www.youtube.com/watch?v=USRyHJAEGE&index=2&list=PLcyIoQku6G2nExUPZpqTrOmU716YvBiS
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Biological structures
The human body is made up of a number of important systems
which work together to help us live.
The systems that are particularly useful to explain behaviour and
psychology of an individual are:
• The nervous system (central NS and peripheral NS)
• The neuron
• The endocrine system(hormones)
The central nervous system
The central NS consists of the
brain and the spinal cord.
It acts as the centre from which all
the physiology of an individual is
controlled.
The brain is the centre of all
conscious awareness.
The spinal cord is an extension of
the brain. It is responsible for reflex
actions e.g. pulling hand away from
hot plate. It passes messages to
and from the brain and connects
nerves to the peripheral NS.
The peripheral nervous system
The PNS transmits messages, via millions of
neurons (nerve cells), to and from the
central nervous system.
It is divided into:
• The autonomic nervous system (ANS)
This system governs vital functions in the
body such as breathing, heart rate, digestion
and stress responses. It is important for
survival.
• The somatic nervous system (SNS)
This system controls muscle movement and
receives information from sensory receptors.
• Sensory neurons carry messages from the PNS to the CNS.
They have long dendrites and short axons.
• Relay neurons (interneuron)- these connect the sensory
neurons to the motor or other relay neurons. They have short
dendrites and short axons.
• Motor neurons connect the CNS to effectors such as muscles
and glands. They have short dendrites and long axons.
The structure of a neuron
• The cell body- contains a nucleus, which contains the genetic
material of the cell.
• Branch-like structures called dendrites protrude from the cell bodythese carry nerve impulses from other neurons towards the cell
body.
• The axon carries impulses away from the cell body. It is covered in a
fatty layer called the myelin sheath that protects the axon and
speeds up transmission of the impulse.
• At the end of the axon are terminal buttons that communicate with
the next neuron in the chain across a gap known as the synapse.
Synaptic transmission
• The process by which neighbouring neurons communicate
with each other by sending chemical messages across the
gap (the synapse) that separates them.
What this video to explain how synaptic transmission occurs in the synapse:
https://www.youtube.com/watch?v=WhowH0kb7n0
Neurotransmitters
• Neurotransmitters are brain chemicals released from
synaptic vesicles that relay signals across the synapse from
one neuron to another.
• Neurotransmitters can be broadly divided into those that
perform an excitatory functions and those that perform an
inhibitory function.
• For example, serotonin causes inhibition, resulting in the
neuron becoming negatively charged and less likely to fire.
• In contrast, adrenalin (element in the stress response) causes
excitation of the post-synaptic neuron by increasing its
positive charge and making it more likely to fire.
The endocrine system
• Works alongside the nervous
system
• Acts more slowly
• Various glands in the body
produce hormones. Hormones
are secreted into the
bloodstream and affect any
cell in the body that has a
receptor for that particular
hormone.
• The major endocrine gland is
the pituitary gland, located in
the brain. It is often called the
‘master gland’ because it
controls the release of
hormones from all other
endocrine glands in the body.