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1. Biological Explanation Mrs Ansell Biological Explanation of Abnormal Behaviour Biological explanation is sometimes known as the Physiological explanation. ã ã ã…
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  • 1. Biological Explanation Mrs Ansell Biological Explanation of Abnormal Behaviour Biological explanation is sometimes known as the Physiological explanation. • • • The demonological model- treatment • Many women were accused of being witches and were subjected to tests where they were thrown into a river, it was believed that a pure woman would sink to the bottom and drown! • Exorcism was carried out by a priest who would attempt to remove evil spirits through prayer, pleas and magic potions. • Trepanning: a hole was drilled into the skull (between 2.5 and 5 cm) of mental patient without an anaesthetic in the hope of releasing evil spirits! • Whether this is effective is debatable, but the operation certainly didn’t cause death because the skulls of some skeletons show evidence of the holes healing and growing over. 1
  • 2. Biological Explanation Mrs Ansell • Comer (1995) starvation, whipping, scalding and stretching was used to drive out the devil. The biological approach • Four main biological processes which cause behaviour…. • Brain damage • Infection • Biochemistry • Genetics Brain damage Abnormal behaviour may occur if the structure of the brain is damaged. This could be via a blow to the head, a tumour or a stroke. A degeneration or malformation of brain cells can cause memory loss often present in Alzheimer’s disease. Korsakoff’s syndrome occurs when drink and drugs damage part of the brain involved in memory. Infection Bacteria and viruses can cause physical and psychological conditions. Syphilis bacterium causes a sexually transmitted disease known as syphilis. It causes short-lived sores followed by general paresis - forgetfulness, mental deterioration and delusions of grandeur and persecution. The influenza virus has been linked to schizophrenia. Brown et al (2004) found that 14% of schizophrenic cases may be linked to the foetus being exposed to the ‘flu virus in the womb during the first trimester. Biochemistry – Neurotransmitters It is suggested that an imbalance of the chemicals which assist or prevent the transmission of messages from one neuron to the next in the CNS may be responsible for abnormal behaviour. 2
  • 3. Biological Explanation Mrs Ansell The brain is composed of 100 billion neurons, with branches that connect to more than a trillion points. Scientists call this branching network ‘a neuron forest’ Signals that form memories and thoughts move through an individual neuron as a tiny electrical current. Nerve cells connect to one another at gaps called synapses. Nerve cells connect to one another at gaps called synapses. When an electrical current reaches a dendrite, at the end of a neuron, it may trigger release of tiny bursts of chemicals called neurotransmitters. 3
  • 4. Biological Explanation Mrs Ansell The neurotransmitters travel across the synaptic gap and attach to receptor sites on the connecting (post-synaptic) neuron which stimulates an electrical impulse. Dopamine is often involved in attention, movement, learning, and reward pathway and is frequently linked to mental disorders E.G. Too much dopamine = Schizophrenia Serotonin (5-HT) is Involved in arousal, sleep, mood, appetite E.G. Too little serotonin = Depression Also not enough noradrenaline has been linked to anxiety disorders, such as phobias. PET scans provide images of the brain and measure the action of neurotransmitters. A drug is injected into the blood stream and travels to the brain and attaches to the neurotransmitter being investigated. Biochemistry – hormones Hormones are part of the endocrine system. They are secreted by glands in the bloodstream The pituitary gland/ The master gland controls all other glands which secrete hormones • The adrenal glands above the kidneys secrete cortisol and adrenaline. Depression and anxiety has been linked to high levels of cortisol. 4
  • 5. Biological Explanation Mrs Ansell The testes secrete testosterone which has been linked to aggression Genes Humans have 23 pairs of chromosomes which carry around 30,000 genes. Genes are the basic units of heredity and influence physical characteristics such as eye colouring. Our genes are made up of DNA. There is strong evidence to suggest that psychological conditions such as schizophrenia, OCD and depression may be inherited as well as physical characteristics and disorders. Evidence for this comes from Twin studies Monozygotic twins (MZ) have 100% identical DNA. Dizygotic (DZ) have 50%. For a behaviour to be solely a genetic cause then if one twin developed schizophrenia then the other would every single time. This would be a concordance rate of 100%. Gottsman and Sheilds (1991) carried out a study and found – 1% risk to normal population – 10% first degree relative – 17% DZ – 48% MZ Both MZ twins develop schizophrenia around 50% of the time. This does support genetic input for the disorder but genetics can only be a partial cause since the concordance rate is not 100% Research has shown that there are low concordance rates in MZ twins for some disorders (such as phobias) and high rates for others (e.g. schizophrenia). Concordance rates are never 100% so there cannot be a purely biological cause. 5
  • 6. Biological Explanation Mrs Ansell The diathesis-stress model can explain this as it is likely that in certain disorders, individuals inherit a predisposition/ susceptibility to the disorder but the disorder only develops if the individual is exposed to an environmental trigger/stressor. 6
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