1. Unit 2 The Biological Approach
Content
CNS, genes, neurotransmitters and hormones

2. We will be examining
The role of the Central Nervous System and Neurotransmitters in human behaviour.

3. The Nervous System has 2 main parts – the Central Nervous System (CNS) and the Peripheral Nervous System (PNS)
The CNS consists of the brain
and the spinal cord.
The brain is protected within the skull and the spinal cord is protected within the vertebrae.

5. Parts of the brain and spinal cord Remember to check out the brain tutorial on I Learn

7. Neurotransmitters
Neurotransmitters are chemical messengers that act between the neurones in the brain. This allows the brain to process thoughts and memories.
Neurones receive and transmit messages, passing them from cell to cell.

8. How Synapses work
You need to be able to explain how messages are passed via neurotransmitters

10. Neurotransmitters continued:
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 fit then the message is blocked.

11. Manufactured drugs work in this way
they are made to mimic neurotransmitters, they more or less fit certain receptors and are received like neurotransmitters.
Some drugs block the message – they fit the receptor, so the natural neurotransmitter cannot pass the message on because the receptor is not available.

12. Place the following in the correct order see worksheet
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.

13. This is an amazing site that will add to your understanding
If you missed the lesson this would be essential viewing!

14. Genes

15. A GENE contains a set of instructions. It is a carrier of information.
A gene consists of a long
strand of DNA
A chromosome is a double
chain of DNA
Every nucleus in every cell in the
body contains a set of 23
Chromosomes.

16. 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.
I may have a genotype which indicates I will grow tall. However if I grow up without adequate nutrition this gene may never become my phenotype

17. 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.

19. Examples of the effects of genes on humans
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

20. Huntingdon’s Disease

21. Environmental triggers on genes
Sometimes genes do not influence physical characteristics unless the ‘right’ environmental conditions occur.
These genes are known as epigenetic

22. PKU

23. 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?

24. In this section we will examine the 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

25. Sex chromosomes
The 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

26. Sex chromosomes

27. Chromosomes & hormones
You can read about this in more detail in your text book.
An embryo will develop as a female unless instructed otherwise
The Y chromosome contains instructions for the embryo to produce androgens (male sex hormones)
These cause the embryo to develop along the ‘male path’

28. Sexual development
At about 6 weeks gestation the GONADS or sex organs begin to develop but there is no difference between the developing sex organs of males and females at this stage.
The SRY gene in the Y chromosome produces a protein called ‘testis-determining factor’ which instructs the gonads to develop into testes rather than ovaries.
Once this has happened hormones take over….

29. HORMONES
Read p106
In your text book

30. There are a number of hormones involved in sex development
H-Y antigen hormone – stop ovaries developing and starts testes development
Anti Mullerian Hormone –prevents the further development of female genitals
Hormones dictate gender differences and cause male and female brains to develop differently!!!! g

31. The Male Brain - Joke!!

32. The Female Brain -Joke!!

33. Seriously though! Abnormal sex differentiation and development
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.

34. Klinefelter’s syndrome
Physical differences (stature, limbs)
Underdeveloped genitalia
Gynaecomastia in some cases
Poor language abilities, learning difficulties
‘Shy and passive’ temperament

35. Klinefelter’s syndrome

36. Klinefelter’s syndrome

37. Turner’s syndrome

38. Turner’s syndrome Physical differences (neck, stature)
Underdeveloped ovaries, lack of menstruation at puberty
Poor spatial and mathematical abilities
Poor social adjustment

39. Turner’s syndrome

40. Hormones 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

41. Hormones 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

42. 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.

43. A great deal of research into hormones and gender development is conducted on animals!

45. Brain Lateralisation see p106
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 e.g.Pfeiffer

48. 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.
Have a go, you may be surprised by what you find out!

49. Evaluation of biological explanations for gender development
We can use 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

50. 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 some 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)

51. Think about Pseudo hermaphrodites – e. g
Think about 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…can you think of an example?