AS Psychology Biological Approach

• The bilogical approach can explain human behaviour through the influence of individual differences of the nervous sytem and genes. 
• DNA make genes, which can be found in the 23 chromosomes we inherit from each parent. They determine physical looks and behviour inherited from family. 
• The CNS (Central Nervous System) is made up of the brain and spinal chord. Behaviour is individual because of the way the CNSinterprets signals sent and recieved form/ to it. 

• Neurons are special type of cell that carries electircal impulses.
• They send signals to between each other using neurotransmitters.
• Neurotransmitters are sent across synaptic gap
• Dendrite receives impulse, impulse goes through cell body, axon, neurotransmitter across synaptic gap, receptor (lock and key- impulse only continues if neurotransmitter fits)

• CNS spinal chord is made up of thick bundle of nerves going down the spine. These branch out and again until individual nerves branch out to reach different body parts
• CNs is communication network, the brain sends and recieves signals through network of nerves
• Some nerves are to brain others from brain
• drugs affect the way nerves work, resulting in loss of control of the body

• We inherit 23 chromosomes from each parent
• Chromosomes contain genes that determine looks and behaviour

• hormones are chemicals released into bloodstream and change a body function
• Pituitary gland releases hromones like testosterone and oestrogen 

• specific area of brain for specific function
• difference in lateralisation between males and females
• hippocampus - memory - london cab drivers - damage like Clive Wearing
• Corpus callosum - connects hemispheres - bundle of neurons - females larger
• hypothalamus - sends signals to pituitary gland
• brain stem - connects brain to spinal chord

• Nature = biological =inherited characteristics causes behaviour
• Nurture = environment

Assumption 1 - Genetic influences

• all fouetes same undeveloped sex organs
• original system could develop into either male or female sex organs
• 6 to 8 weeks gonads start developing, potential to become either testes or ovaries
• chromosomes determine sex. If ** female. If XY male.
• SRY gene attached to Y chromosome produces protein TDF (Testes Determining Factor)
• TDF influences development of gonads- to become testes
• females no Y chromosome - no SRY - no TDF- default mode- deveopment of gonads to become ovaries

Assumption 2 - Hormones

• 8 to 12 weeks  differentiation of external genitalia determined by presence/absence of male hormones
• male hormones= androgens= e.g. testosterone
• 6-8 weeks protein hormone HY-antigen released if Y chromosome
• encourages development of testes whilst stopping ovary development
• Testes release anit-mullerian hormone (MIS) stops ovary development
• testes produce androgens = stimulates development of full male sex organs
• 3 months prenatal development Wolffian system develop into full male sex organs

Assumption 2 - Hormones cont.

• absence of androgens
• no HY antigen and no MIS
• gonads development into ovaries
• Mullerian system develop female sex organs

• puberty = secondary sexual characteristics = x2 e.g.

Assumption 3 - Brain lateralisation

• if testosterone present = hypothalamus signals for pituritary gland to release more male hormones
• if more oestrogen = hypothalamus signals for pituitary gland to release more female hormones
• speech and comprehension - males left- females both - men more effected by stroke as lateralised brain
• spatial awareness - males right - females both

 For: supporting research

• David Reimer - born XY and male- circumcision accident burnt off penis - raised female - behaviour more masculine- surgery to turn back male - biology (nature) hormones stronger than  upbringing (nurture) - genetics stronger 
• Reiner & Gaerhart - 14/16 males raised females because of no or small penis but XY and testes but later chose to live as male - nature stronger even with surgery 
• Dorner rat studies- destroyed sex centres of male rats brains and behaviour female - female rats injected male hormones act male - hormones large control over biology giving us gender 
• Pfier's rat studies - removed sex organs-male rats acted female- transplant testes on to female rats released male hormones - no testosterone gender default  female 

•  Weakness of animal research - brains diferent - not human - not ethical on humans - quicker prenatal development (22 days)

For and against: Research = for hormones against genes

• Batista family - mutant recessive gene caused born female genitalia but XY chromosome
• Puberty surge tesosterone causd other male hormones lacked before birth
• developed full male genitalia and adopted new gender
• supports hormones control development of sex organs and genitals - surge cause to correct genitals to match chromosomes
• against genetics - chromosmes (XY) automatically stimulate male hormones and male genitalia development

For and against supporting research: for hormones, against genetics

• Pseudo-hermaphrodites = chromosomally one sex, physically appearance opposite sex and raised that way
• androgenital syndorome= ** exposed too much androgens (male hormones) and so develop male genitals = e.g. Daphne Went
• androgen insensitivity syndrome = XY lacks exposure of androgens and develop female genitals
• support prenatal exposure to hormones determines gender development
• against genetics, should automatically encourage correct hormone production

Research against:

• Samoan Fafafinis = +2 gender roles = no girl then boy chosen to be raised female
• Fafafinis do 'female' gender stereotypical role like housework but viewed more effective (i.e. strength)

Alternative theories:

• Learning - get gender through operant conditioning and social learning
• Psychodynamic - get gender by oepedius or electra complex, and unconcious influences

1. MZ vs. DZ

Monozygotic twins

• share 100% DNA
• share same environment
• high concordance rate [similarity] (intelligence 99%)

Dyzygotic twins

• share 50% DNA
• share same environment
• low concordance rate (intelligence 10%)

Intelligence genetic?

2. MZ vs. MZ reared apart

• high concordance with MZ vs DZ could be because share same environment
• sepearate nature and nurture by study 100% same DNA, 0% same environment

Strengths:

• MZ and DZ twins share same enviro. = natural control of enviro. effects
• only MZ twins share all DNA = test influence of genes

Weaknesses:

• MZ treated more same than DZ (appearance more similar) = enviro. not as controlled
• MZ same DNA but environmental influences switch genes on/off = epigenetic modification = become different

• similarities between adopted child and adoptive parents = nurture = no shared genes = behaviour learnt
• similarities between adopted child and biological parents = nature = share genes cause behaviour

e.g. language abiility

• score closer to adopt. parents = learnt 
• score closer to bio. parents = genetics and inheritance

Strengths:

• control enviroment influences = different environment to bio. parents= similarties of bio. parents genetic
• longtiduinal studies =development trends over years

Weaknesses:

• adopt. parents enviro. similar to bio. parents enviro. = not cause stress= no difference
• adopt. parents all similar, causing results (e.g. care over language ability help)

• scan = non-invasive imaging method of body and organs

PET scans (Positron Emmission Tomography)

• measure brain function and activity
• radioactive tracer injected into blood, breaks down and sensed
• more active area, more radiation, more glucose used (energy)
• dark, warm colours (red/orange) = high activity   
• cool/light colours (blue/green) = less activity
• e.g. Raine
• cancer detection = red = cells lots energy for metabollic rate

MRI (Magnetic Resonance Imaging)

• measures brain structure
• use magents not x-rays for image production
• strength of magnetic field causes body atoms respond
•  emissions detected and analyzed
• create layers image