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Chapter 2


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Konstantine Zakzanis

CHAPTER 2: Current Paradigms and the role of cultural factors The Role of Paradigms - Philosopher Thomas Kuhn, subjective factors as well as limitation in our perspective on the universe enter into the conduct of scientific inquiry. - Paradigm: the conceptual framework or approach within which the scientist works. It is a set of basic assumptions that outline the particular universe of scientific inquiry. They are an intrinsic part of science serving the vital function of indicating the rules to be followed. It injects inevitable biases into the definition and collection of data and may also affect the interpretation of facts. The Biological Paradigm - A broad theoretical view that holds that mental disorders are caused by some aberrant somatic process or defect. Often referred to as the medical model or disease model. - Medical illnesses all share one characteristic, where in all of them some biological process is disrupted or malfunctioning hence biological paradigm. Behaviour Genetics - Genes: an ultramicroscopic area of the chromosome; it is the smallest physical unit of the DNA molecule that carries a piece of hereditary information - Behaviour Genetics: the study of individual differences in behaviours that is attributable in part to differences in genetic makeup. - Genetic makeup: total genetic makeup of an individual consisting of inherited genes. - Genotype: an individuals unobservable genetic constitution. - Phenotype: totality of an individuals observable and behavioural characteristics such as anxiety level. It changes over time and is the product of an interaction between the genotype and the environment. Ex; an individual may be born with the capacity for high intellectual academic but whether they develop this genetically depends on environmental factors such as upbringing and education. - The study of behaviour genetics has relied on 4 basic methods to uncover whether a predisposition for psychopathology is inherited: comparison of members of a family, twins, investigate adoptees and linkage analysis. - Family Method: used to study a genetic predisposition among members of a family because the average number of genes shared by 2 blood relatives is known. First degree relatives are people who share 50% of their genetic background. Second degree relatives are people who share 25% of the genetic makeup. - Index cases or probands: the person who in a genetic investigation bears the diagnosis or trait in which the investigator is interested. If a persons relatives have it then they have a higher rate of getting the disease than the general population. - Twin Method: (Monozygotic twins are genetically identical siblings who have developed from a single fertilized egg sometimes called identical twins(same sex) and dizygotic twins(same sex or opposite sex) are fraternal twins because birth partners who have developed from separate fertilized eggs and who are only 50% alike genetically) This study begins with diagnosed cases and then search for the presence of the disorder in the other twin. - Concordance: when the twins are similar diagnostically they are concordant. Disorder should be higher in MZ pairs than DZ pairs if so then the characteristic is inheritable. - Equal environment assumption: environment assumption is that the environmental factors that are partial causes of concordance are equally influential for MZ and DZ pairs. - Adoptees method: study children with abnormal disorder who were adopted and reared apart from their parents. This situation has the benefit of eliminating the effects of being raised by disordered parents. Molecular Genetics - It tries to specify the particular gene or genes involved and the precise functions of these genes. - Allele: any one of several DNA codings that occupy the same position or location on a chromosome. A persons genotype is their set of alleles. - Genetic polymorphism; variability among members of the species. It involves differences in the DNA sequence that can manifest in very different forms among members in the same habitat. - Linkage analysis: a method in molecular genetics that is used to study people. Researchers usually study families in which a disorder is heavily concentrated and study genetic markers. Ex; eye colour is controlled by a specific location on a specific chromosome. If the occurrence of a form of psychopathology among relatives goes along with the occurrence of another characteristic whose genetics are known, it is concluded that the gene predisposing individuals to the psychopathology is on the same chromosome and in similar location to it as the gene controlling the other characteristic. - Gene environment interactions: the notion that a disorder or related symptoms are the joint product of a genetic vulnerability and specific environmental experience or conditions. Its becoming a predominant theme in depression. Neuroscience and Biochemistry in the Nervous System - Neuroscience is the study of the brain and the nervous system which has a lot of neurons (a single nerve cell). Each neuron has 4 major parts: 1) cell body 2) dendrites (short and thick extensions) 3) one or more axons of varying lengths (usually one long and thin axon extending a considerable distance from the cell body) 4) terminal buttons on the many end branches of the axon. - A neuron is appropriately stimulated at its cell body or through its dendrites, a nerve impulse which is a change in the electric potential of the cell, travels down the axon to the terminal endings. Between the terminal endings of the sending axon and the cell membrane of the receiving neuron there is a small gap called synapse. - For a nerve impulse to pass from one neuron to another and for communication to occur, the impulse must have a way of bridging the synaptic gap. The terminal buttons of each axon contains synaptic vesicles; small structures that are filled with neurotransmitters which are chemical substances that allow a nerve impulse to cross the synapse. - Nerve impulses cause synaptic vesicles to release molecules of their transmitter substances and these molecules flood the synapse and diffuse toward the receiving or postsynaptic neuron. - The cell membrane of the postsynaptic cell contains proteins called receptor sites that are configured so that specific neurotransmitters can fit into them. When neurotransmitter fits into a receptor site, a message can be sent to the postsynaptic cell. - These messages can be excitatory leading to the creation of a nerve impulse in the postsynaptic cell or inhibitory making the postsynaptic cell less likely to fire. - After the presynaptic neuron (the sending neuron) has released its neurotransmitter, the last step of the synapse is to be returned to its normal state. - Not all neurotransmitters had found its way to postsynaptic receptors. Some of the synapse is broken down by enzymes and some is pumped back into the presynaptic cell through a process called reuptake. Too much or too little of a particular transmitter could result from an error in these metabolic pathways. - Norepinephrine, a neurotransmitter of the peripheral sympathetic nervous system is involved in anxiety disorders. - Serotin (depression) and dopamine (schiz) are both neurotransmitters in the brain. The decrease of these neurotransmitters during puberty contributes to the increase risk of psychopathology in adolescence. F.O.D: Structure and function of the human brain - The brain is enveloped within 3 layers of non-neural tissue referred to as meninges. From the top the brain is divided into 2 mirror image cerebral hemispheres together constituting most of the cerebrum(the thinking centre of the brain). The major connection between the 2 hemispheres is a band of nerve fibres called the corpus callosum. - Cerebral cortex consists of 6 layers of tightly packed neuron cell bodies with many short, unsheathed interconnecting processes. The cortex is vastly convoluted; the ridges are called gyri and depressions between them sulci or fissures. - Deep fissured divide the cerebral hemispheres into several distinct areas called lobes. Frontal lobe (reasoning and other higher mental processes, voluntary movement) lies in front of the central sulcus; the parietal lobe is behind it and above lateral sulcus; temporal lobe (sound) is located below the lateral sulcus; and occipital lobe (vision) lies behind he parietal and temporal lobes. - The 2 hemispheres of the brain have different brains. Left hemisphere controls the right half of the body because of the crossing over of motor and sensory fibres, speech, analytical thinking, etc. The right hemisphere controls the left side of the body and is involved in emotion and sensitivity.
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