Transcript The role of the Central Nervous System and

The role of the Central
Nervous System and
Neurotransmitters in
human behaviour.
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The Nervous System has 2 main parts – the Central
Nervous System (CNS) and the Peripheral Nervous
System.
The CNS consists of the brain
and the spinal cord.
The brain is within the skull and the spinal cord is within
the vertebrae.
Parts of the brain and spinal cord
Remember to check out the brain tutorial on I Learn
The Brain
Neurotransmitters
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Neurotransmitters are chemical messengers that act between the neurones
in the brain. This allows the brain to process thoughts and memories.
The nervous system contains neurones and glia – glial cells carry out
repairs and remove waste products from the brain.
Neurones receive and transmit messages, passing them from cell to cell.
How Synapses work
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You need to be able to explain how
messages are passed via
neurotransmitters
Neurotransmitters continued:
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RECEPTORS can be thought of as locks – if a
certain chemical (neurotransmitter) fits like a
key, then the message is passed on: if it does
not then the message is blocked.
Manufactured drugs work in this way – they
mimic neurotransmitters, more or less fit certain
receptors, are received like neurotransmitters
and the message from them ‘works’. Some
drugs block the message – they fit the receptor,
so the natural neurotransmitter cannot pass the
message on because the receptor is not
available.
Place the following in the correct order see worksheet
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The axon terminal of one neurone reaches to the
dendrites of another.
The synaptic gap or cleft sits between two neurones.
At one end, a neurone has dendrites which surround the
nucleus.
On one side, at the dendrites, there are receptors of a
certain shape, prepared to receive the neurotransmitter
from another neurone.
From the nucleus, there is a long extension called an
axon, which reaches to an axon terminal.
If the neurotransmitter fits the receptor the message is
passed on; if it does not, the message is blocked.
Between the terminal and the dendrites, there is a gap
called a synapse.
Genes
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A GENE contains a set of instructions and is a
carrier of information.
Each individual human has a genotype – this is
the genetic composition
Each person has a phenotype which is what the
individual becomes when their genes interact
with each other and the environment.
A gene consists of a long
strand of DNA
A chromosome is a double
chain of DNA
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Some genes always lead to certain
characteristics; these are known as dominant
genes – to produce a characteristic, dominant
genes need to be on only one pair of
chromosomes.
Some genes need more than one copy to
produce a characteristic; these are known as
recessive genes – if a recessive gene is present
on only one of the pair of chromosomes, the
characteristic will not appear.
However, they can be passed on and may
appear in a future generation.
Characteristics can be aspects of appearance,
personality or behaviour.
Examples of the effects of genes on
humans
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Some diseases and characteristics are sex linked – they
are controlled by the sex genes. E.g. most colour blind
people are men
If one parent contributes two copies of chromosome 21,
then the child has three copies and the consequence is
Down’s Syndrome.
Human chromosome 4 has a marker known as G8 – if a
parent and child both have Huntingdon’s Disease, then
in 98% of cases they both have the same form of G8
marker – suggesting that the gene for Huntingdon’s
travels with the G8 marker
Huntingdon’s Disease
Environmental triggers on genes
Sometimes genes do not influence
physical characteristics unless the ‘right’
environmental conditions occur.
 Find out about PKU (phenylketonuria) –
what is it? How can the damage from this
condition be reduced?
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PKU
The Nature – Nurture Debate
What do psychologists mean when they
talk about the nature – nurture debate?
 Write down some characteristics that you
have which you believe are caused by
nature.
 Write down some characteristics that you
have which you believe are caused by
nurture.
 Which characteristics may be caused due
to an interaction between nature and
nurture?
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Biological explanations for gender
development – we will….
Consider how biological psychologists
might explain sex & gender
 Examine chromosomal influences on
sex/gender development
 Examine hormonal influences on
sex/gender development
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Sex chromosomes
Genetic blueprint for a person is organised
into 23 pairs of chromosomes
 22 pairs are both X shaped. the 23rd
depends on whether the person is female
or male
 XX – female
XY - male
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Sex chromosomes
Chromosomes & hormones
Everything develops as a female unless
instructed otherwise
 The Y chromosome contains instructions
for the body to produce androgens (male
sex hormones)
 These cause the embryo to develop along
the ‘male path’
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Sexual development
At about 6 weeks gestation the GONADS
or sex organs begin to develop but there is
no difference between developing sex
organs of males and females at this stage.
 Later, the gonads begin develop differently
 What does the gene in the Y chromosome
called SRY do?
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HORMONES
Which protein hormone is released at
about 6 weeks into foetal development?
 What does this hormone do?
 What are the undeveloped sex organs of
both men and women called?
 What is the name of the first hormone to
be released by the testes and what does it
do?
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Abnormal sex differentiation and
development
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Problems with sex differentiation can occur at any time
during development.
Problems can arise at fertilisation – e.g. boys with XXY
chromosomes develop Klinefelter’e syndrome and girls
with XO chromosomes have Turner’s syndrome.
Incorrect Mullerian or Wolffian duct development can
also cause problems – the foetus might not respond to
androgens, in which case the foetus will have neither
male nor female internal duct structures and lack of the
Mullerian (female) inhibiting substance but with
androgen secretion can lead to a foetus having both
male and female duct structures.
Klinefelter’s syndrome
Physical differences (stature, limbs)
 Underdeveloped genitalia
 Gynaecomastia in some cases
 Poor language abilities, learning difficulties
 ‘Shy and passive’ temperament
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Klinefelter’s syndrome
Klinefelter’s syndrome
Turner’s syndrome
Turner’s syndrome
Physical differences (neck, stature)
 Underdeveloped ovaries, lack of
menstruation at puberty
 Poor spatial and mathematical abilities
 Poor social adjustment
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Turner’s syndrome
Hormones and Gender Development
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Like neurotransmitters, hormones carry
messages
However, the messages are passed much more
slowly because hormones travel in the
bloodstream
They affect numerous
processes such as growth,
development, mood and
metabolism
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They are produced by endocrine glands, which
are groups of cells and include the pituitary,
thyroid and adrenal glands
They are also produced by males in the testes
and females in the ovaries
The female hormones are oestrogen and
progesterone
The male hormones are androgens such as
testosterone
Collectively these are called reproductive organs
These dictate gender differences and cause the
male and female brains to develop differently
The Male Brain
The Female Brain
Hormone differences can affect health and
lifestyle throughout a person’s life.
 For example – more females develop pain
syndromes like fibromyalgia and they also
tend to suffer more from mood disorders
such as depression and anxiety. On the
other hand, more men than women are
likely to develop alcoholism and to abuse
drugs.
 Find out about ANDROGENITAL
SYNDROME – Cause? Symptoms?
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Brain Lateralisation
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What is meant by the term brain lateralisation?
What are the 2 parts of the brain known as?
What connects the 2 parts of the brain?
It is claimed that the left and right sides of the
brain are concerned with different things – what
are these?
What evidence is there for brain lateralisation?
You will need evidence from studies here
e.g.Pfeiffer
Test your Brain Sex
You can do this by logging on to the
following link and completing the test – it
will take about twenty minutes.
 http://www.bbc.co.uk/science/humanbody/
sex/index_cookie.shtml
 Please do this and print out your findings –
bring to class after half term
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Evaluation of biological explanations for
gender development
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The Case of David Reimer
The results of biological explanations are based
on tests that can be repeated e.g. injecting rats
with additional testosterone or using MRI
scanning in humans to detect blood flow. The
results are replicable and can be shown to be
reliable
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Different research methods are used and tend to
come up with similar results e.g. sex differences
in brain lateralisation.
There is a problem with generalisability because
many findings come from animal studies; there
are important differences in the human brain, so
such findings may not be relevant to humans
and may not be credible.
Biological aspects are difficult to study without
reference to the environment; for example male
and female children are reinforced for different
behaviour; this may mean that they use different
strategies to do tasks rather than that they have
different brain structures (SLT)
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Pseudo hermaphrodites – e.g. Daphne Went –
this evidence refutes the genetic explanation of
gender development. How?
Androgenital syndrome and Androgen sensitivity
syndrome support the argument that pre natal
exposure to certain hormones determines
gender development – hormone exposure can
override genetic sex.
There is an argument that gender is a result of
interaction between biology and environment.
From the moment a child is conceived, it is
subject to influence from the environment.