Dummies guidebiologicalapproach
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The biological approach focuses on three key areas: 1) Genetic influences on behavior and inheritance of traits from parents. 2) The role of neurotransmitters in the brain and how they guide behavior. 3) Differences in brain structure between areas and between males and females. Research methods examined include twin and adoption studies to analyze genetic and environmental factors, as well as scanning techniques like PET and MRI to study brain activity and structure. While animal studies provide some insights, they have limitations in applicability to humans given biological differences.
Dummies guidebiologicalapproach
- 1. The Dummies Guide to the Biological approach Key assumptions 1) The importance of genetic influences on behaviour: The physiological approach see us as being to a large extent who and what we are by the genes inherited from our parents. We inherit 50% of our genes from our mother and 50% from our father. The more closely related two people are the more likely they will share the same characteristics (e.g. IQ, height, schizophrenia etc). A person has their ‘nature’ which is given to them by their genes, and a ‘nurture’ which is given to them by their environment. 2) The role of neurotransmitters on behaviour: The central nervous system consists of our brain and spinal cord. The automatic nervous system (ANS) which controls functions of the body such as the heart, lungs etc, which we have no conscious control. The Peripheral nervous system (PNS) controls those parts of the body to which we have conscious control such as flexing muscles. The brain guides behaviour through neurotransmitter functioning. 3) Brain Structure and behaviour: The brain has many parts, hippocampus is thought to be where STM occurs, and the hypothalamus produces hormones that influences gender during pregnancy. The brain is in 2 halves, joined by a mass of bundles called the corpus callosum. Brain lateralisation is the term used for considering the two halves of the brain separately and studies have shown that males and females use these hemispheres differently. THE CENTRAL NERVOUS SYSTEM Our nervous system is activated when we receive a stimulus from the environment and respond to it, the messages are transmitted by a series of electrical impulses through nerve cells. Neurotransmitters are chemical messengers that travel in the brain between neurons. • An electrical impulse travels down the axon and releases the neurotransmitter into the synaptic gap • The receptors on the nearby dendrite receives the neurotransmitter if it ‘fits’ or not. (lock and key) • If it is not taken up the message is stopped • If it is taken up the message continues to travel down that neuron’s axon so the message continues. GENDER DEVELOPMENT/SEX DIFFERENTIATION Gender= social term that refers to the norms and rules of being male or female Sex = biological term that refers to our genetic sex, male or female. We have 23 pairs of chromosomes, each pair comes from our mother or father. (50%) a male baby receives (XY) and female (XX). An embryo generates hormones within 8 weeks. The hormones influence the sex of the baby. Hormones also carry messages and are produced by the endocrine gland. They travel in the blood and are a lot slower than neurotransmitters. Sex differentiation goes through 4 steps • Fertilization determines the genetic sex (XX) or (XY) • During development the sex organs grow and a gonadal ridge develops. External genitalia look female. • Hormones (androgens) start affecting how the fetus develops • The gonadal ridge changes, in males testes are developed, in females ovaries develop MALES: Testosterone and androgens FEMALES: Oestrogen and progesterone BRAIN LATERALISATION There are brain differences between males and females. The brain is divided into 2 hemispheres which are joined by the corpus callosum which is larger in women. The left half controls language and the right is concerned with visuospatial ability and perception. Evidence comes from scanning techniques: • If male has damage to RH then visuospatial tasks are affected
- 2. • Men who do not have normal exposure to androgens tend to use both sides of the brain more • High levels of testosterone means slower neuron growth in the LH which supports males using the RH more. Strengths of biological explanation of gender development: high reliability because studies are replicable. Any experiment using animals or humans are objective and scientific. There is validity because different studies use different research methods have similar findings. (MRI scans, lab expt etc.) Weakness of biological explanation of gender development: difficult to generalise because many findings come from animal studies. There are important differences in the human brain so findings not credible. Can’t ignore influence of the environment in behaviour. METHODOLOGY TWIN AND ADOPTION STUDIES Twins: MZ = share 100% genes and are identical as they come from the same egg and are normally the same gender DZ = share 50% genes, non identical (fraternal) as they come from different eggs and can be different genders. If a characteristic (Schizophrenia, alcoholism, depression etc) is due to genes then MZ twins should share that characteristic. Strengths: there is no other way to study genetic influences clearly, MZ and DZ share same environment so there is a natural control over environmental effects Weaknesses: MZ have identical DNA but they may gown and develop differently due to environmental influences. (Nature/nurture). MZ are normally treated the same by parents and others so environment may not be as controlled as may be thought. Adoption: Looking at children who are adopted and then comparing their characteristics with their biological and adoptive parents. If a child develops depression and the biological parents also have depression but not the adoptive parent then it can be argued that the characteristic has been inherited through the genes. Strengths: they control for the environment because children do not share the same environment as their biological parents. Studies can be longitudinal so any trends can be studied. Weakness: families that adopt are similar to each other so there may be something in that similarity. Because they are chosen for similarity the environment and upbringing may not be very different. PET AND MRI SCANNING TECHNIQUES PET scans involve producing computer generated pictures of the brain. A radioactive tracer is injected that emits a signal that can be picked up and formed into a picture of how much tracer is absorbed by the area of the brain that is functioning. The PET scan measures blood flow and oxygen/glucose use. MRI Scans is a technique that use magnetic and radio waves that pass through the body when the person lies in the large cylinder. The scanner picks up signals of the body’s atoms move back into positron and the computer turns the signals into a picture. Strengths: Non-invasive, scans are accurate, reliable, MRI gives clearer pictures than PET s cans. The person is alive! Weakness: Expensive, care must be taken to interpret the results. PET scans don’t show a fine image, ethical issue of injecting radioactive substance. USING ANIMALS IN EXPERIMENTS Animals are used in a number of areas of study (language, memory and learning) in particular how the brain works and the effects of genes. You need to know two studies and describe and evaluate those studies. Consider, ethics, practical issues and credibility. (Pavlov’s dogs and Skinner’s superstitious pigeons are good examples to use) Practical issues: FOR AGAINST • Small and easy to handle • Brains are not going to be identical to humans • Short reproductive cycles • Genetic structures are not the same • Similar brain structure to humans • Human lives are complex • Short lifespan • Some diseases have to be replicated in animals using • Strict control of procedures drugs and so might not be the same thing
- 3. Ethics: REASONS WHY GUIDELINES • It is possible to carry out some procedures A – Anaesthetic given that you cant do on humans N – non animal expts cant be used (Cutting/damaging parts of the brain) I – important enough to justify? • We should protect humans first, animals M – minimum used come second A – appropriate accommodation • Drugs have been developed that could not L – legislation followed have been developed otherwise S – specialist and competent staff • Knowledge obtained helps animals too Credibility: SUBJECTIVE OBJECTIVE Does the data make sense to draw conclusions from How strong is the data in respect of how good the animals to humans? methodology is. Using animals can be seen as lacking credibility because Using animals is scientific because there can be controls people think that animals are too different to humans for and studies can be repeated to make sure the findings are the results to apply reliable. MONEY 1975 Aims: Wanted to find out about sex reassignment Case Background/procedure: looked at an MZ boy (David Reimer) brought up as a girl after a circumcision went wrong Case Description: The baby’s penis was burnt off accidentally because the electric current was too strong. The parents contact Money and chose to go for sex reassignment. They treated ‘Brenda’ as a girl and encouraged her to be socialized in female role. Hormone replacement therapy and surgery was used as child developed. ‘Brenda’ was reported to have tomboy traits and being physically active. Case analysis: Money concluded that a normal XY baby could be successfully nurtured as a girl and therefore stronger than nature. ‘Brenda’ was told the whole story at 15yrs and it emerged that she was never happy as a girl. His mother attempted suicide and his father turned to alcohol. His brother became clinically depressed so the family was under enormous pressure. ‘Brenda’ underwent surgery, was depressed and attempted suicide himself. However, he married and had a job. His brother dies of an overdose and David had marital problems and eventually committed suicide. Strengths: Case is detailed and longitudinal giving it validity. Qualitative data from various sources. Observation, questionnaires and interviews from parents. Brenda’s self report. Weakness: David was not happy as a girl so no validity. Hard to generalise as unique case. RAINE 1997 Aims: Wanted to find out about brain differences between murderers pleading NGRI and non-murderers. Sample and Design: 41 murderers charged with manslaughter. 23 had history of brain damage, 6 with schizophrenia, 3 with substance abuse, 2 with mood disorder, 2 with epilepsy , 3 with learning disability and 2 with paranoid personality. The control group was matched for these features. The study took place in a University in USA. IV = whether participant was a murderer or not DV = various measures of brain activity Procedure: Each PPt carried out a practice test and then injected with a trace, then given more tests. After ½ hr a PET scan was taken. Slices of the scan were checked for glucose levels and compared with the controls. Results: murderers had lower glucose metabolism in some prefrontal areas. There were no differences in the temporal lobe. The murderers had lower glucose in the corpus callosum and had different levels of activity in the area of the brain linked to aggression. Conclusions: murderers have lower glucose activity levels and abnormal activity in other areas. Suggest biological cause. Could not conclude biological cause for violence just a predisposition for it depending on the environmental triggers (nurture). Strengths: PET scanning is objective and results can be interpreted by more than one person. It is scientific and reliable. Sample size is large enough for generalisation to murderers pleading NGRI
- 4. Weakness: there were no violent criminals in control group so hard to generalise beyond study. Does not show biological causes for violence because environment can cause brain differences. KEY ISSUE Some people argue that, because it is easier to create working female sex organs than working male sex organs, the decision over which gender to raise a child may be driven by this rather than what is best for the child, therefore making surgery unethical. Evidence of transsexual from the ancient world and castration and penectomies were common in China and Rome. Male to female surgery began in 1951 in UK and in 1930s in Germany. Hormone therapy dates back to early 1920s. In 1970 a transsexual could not marry a female as he/she was still legally a man. Money’s case describes how the David was not happy as a girl. But some people feel that their minds and bodies don't quite match up. The case of Tracy Lagondino who had a sex change operation and later gave birth as a man. The issue is whether the procedure for sex reassignment is ethical, what would it involve? Who decides? Should it be different for children? Sex reassignment is not frequently undertaken but is documented over the years in many different countries so is an issue worth considering. Sex reassignment would involve changes in hormones and also reconstructive surgery, both of which should not be undertaken lightly and there is an ethical discussion over when such biological interventions should be allowed and what measures should be taken to ensure such procedures are ethical. There is, for example, the issue of whether only adults should be treated, since children cannot give consent and parents usually consent for them. On the other hand, reassignment as a child might be more straightforward, and biological interventions might be safer then as well. The question is should transgender operations be undertaken at all, and if so, when it is ethical to carry out such interventions and when is it not ethical? Transgender operations involve altering hormones and genitals to represent the desired sex and this can involve extensive interventions. One argument is that such procedures are not ethical because on the face of it there is no need as the person is not ill. However, it is accepted by most people now that mentally a person can feel very uncomfortable in their body and this is accepted to an extent as a mental disorder, so surgery and medical procedures might be judged ethical. Work with rats and mice, as well as research with humans, has shown that genes direct hormones and other processes so that from about 6 weeks old the foetus will start to develop as male or female according to their genes. The XX sex chromosomes lead to a female child and XY to a male child. In the XY pairing androgens are released and they trigger the genitals to be male, otherwise the foetus will remain and grow as a female. _ At birth an infant will be assigned as male or female often purely from external genitalia, and it is not hard to see that this can lead to an error as there is evidence for a few ‘abnormalities’ in the foetus’s development that can lead to mis-assignment. Something in the releasing of the hormones can go wrong, as can the acceptance of the hormones, as well as the chromosomes in the first place. For example, there are examples of XXY patterns, and examples of androgenital syndrome. It could be argued that tests for these sorts of abnormalities should be carried out before sex assignment takes place. It could be argued that it is more ethical to reassign someone who has been wrongly assigned for clear biological reasons such as these than to reassign someone who ‘feels’ wrongly assigned, but there is not obvious cause. However, feelings are important too, so if reassignment is ethical for one reason (a biological one) perhaps it should be for another (a less obvious one). Gender development appears to be affected by brain lateralisation too and perhaps brain differences lead to the feelings of being wrongly assigned although we don’t as yet have the equipment or knowledge to pinpoint such causes. Money documented the case study of an identical twin boy who had surgery go wrong and was brought up as a girl. Then the ‘girl’ when an adult explained that ‘she’ had never felt comfortable as a girl and David became male. His story suggests that biological sex is very important to how someone feels, so if someone feels they are the wrong gender there is some evidence at least that it would be unethical to prevent them from becoming what they felt they should be.