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Chapter 2

PSYB32 Chapter 2.doc

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Konstantine Zakzanis

CHAPTER 2: CURRENT PARADIGMS AND THE ROLE OF CULTURAL FACTORS PAGES 38- 82 (44 pages) PART I: THE ROLE OF PARADIGM - Central to any applicant of scientific principles, in Kuhns view, is the notion of para- digm, the conceptual framework to approach within which scientist works. - A paradigm is a set of basic assumptions that outline the particular universe of scien- tific inquiry. - Paradigms specify what problems scientists will investigate and how they will go about the investigation. - Paradigms are an inartistic part of a science, serving the vital function of indicating the rules to be followed. - A paradigm injects inevitable biases into the definition and collection of data, and may also effect the interpretation of acts PART II: THE BIOLOGICAL PARADIGM - The biological paradigm: of abnormal behavior is a continuation of the somatogenic hypothesis. - This broad perspective holds that mental disorders are caused by aberrant biological processes. - This paradigm has often been referred to as the medical model or disease model - Medical illnesses can differ widely from one another in their cause, however they all share one characteristic: in all of them, some biological process is disrupted or not func- tioning normally. - The biological paradigm was the dominant paradigm in Canada and elsewhere from the late 1800s until at least the middle of the 20 century. Contemporary Approaches to the Biological Paradigm Behavior Genetics - When the ovum, the female reproductive cell, is joined by the males spermatozoon, a zygote, or fertilized egg, is produced. - It has 46 chromosomes, the number characteristic of a human being. - Each chromosomes is made up of thousands of genes-the carriers of the genetic in- formation (DNA) passed from parents to child. - Behavior genetics is the study of the individual differences in behavior that are attrib- utable in part to differences in genetic makeup. - The total genetic makeup of an individual, consisting of inherited genes, is referred to as the genotype. - An individuals genotype is his or her unobservable genetic constitution; in contrast an individuals phenotype is the totality of his or her observable, behavioral characteristics (i.e. Level of anxiety) - The genotype is fixed at birth, but it should not be viewed as a static entity. - Genes controlling various features of development switch off and on at specific times to control aspects of physical development. - The phenotype changes over time and is viewed as the product of an interaction be- tween the genotype and the environment. - Ex. A person may be born with the capacity for high intellectual achievement, but whether he or she develops this genetically given potential depends on such environ- mental factors as upbringing and education - It is critical to recognize that various clinical syndromes are disorders of the phenotype, not the genotype. - The study of behavior genetics has relied on 4 basic methods to uncover whether a predisposition for psychopathology is inherited: - 1. Comparison of members of a family - 2. Comparison of pairs of twins - 3. The investigation of adoptees - 4. Linkage analysis. - The family method can be used to study a genetic predisposition among members of a family because the average number of genes shared by 2 blood relates is known. - People who share 50% of their genes with a given individual are called first degree rel- atives of that person. - Nephews and nieces share 25% of the genetic makeup of an uncle and are called sec- ond degree relatives. - The starting point for these investigations is the collection of a sample of an individual who bear the diagnosis in question-these people are referred to as index cases or probands. - In the twin method both monozygotic (MZ) twins and dizygotic (DZ) twins are com- pared. - MZ twins develop from a single fertilized egg and are genetically the same. - DZ pairs develop from separate eggs made are on average only 50% alike genetically, no more alike than any other 2 siblings. - MZ twins are always the same sex, but DZ twins can be either the same or the oppo- site sex. - Twin studies begin with diagnosed cases and then search for the presence of the dis- order in the other twin. - When the twins are similar diagnostically, they are said to be concordant. - To the extent that a predisposition for a mental disorder can be inherited, con- cordance for the disorder should be greater in genetically identical MZ pairs than in DZ pairs. - When the MZ concordance rate is higher than the DZ rate, the characteristic be- ing studied is said to be heritable. - The ability to offer a genetic interpretation of data from twin studies hinge on what is called the equal environment assumption. - The EES is that the environmental factors that are partial causes of concor- dance are equally influential in MZ pairs and DZ pairs. - The assumption of equality applies only to factors that are plausible environmental cause of psychopathy. - The equal environment assumption would assert that MZ pairs and DZ pairs have equivalent numbers of stressful life experiences. - One factor can also complicate the results of twin research-in a study of post traumatic stress disorder they identified 3 factors as biasing heritability estimates - 1.violation of the equal environments assumption - 2.the sex of the participant - 3.his or her age when the assessment took place. - When they controlled statistically for the effect s of age and sex differences, they found that genetic and non-shared environmental factors contributed to symptoms of post- traumatic stress disorder - Analyses of the role of these factors in a persons exposure to traumatic events re- vealed that only environmental factors contributed to exposure to events involving non- assaultive traumas, but both genetic and environmental factors contributed to exposure to assaultive traumas - Thus, genetic factors may determine, in part the extent to which a person is likely to experience post traumatic stress after an assaultive traumas - However is limited because it had to rely on self report measures of trauma - Researchers using the adoptees method study children with abnormal disorders 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 - Molecular genetics is a highly advanced approach that goes beyond mere attempts to show whether a disorder has a genetic component; it tries to specify the particular gene or genes involved and the precise functions of these genes. - Each cell consists of 46 chromosomes (23pairs) with thousands of genes per chromo- some. - The term genetic polymorphism refers to 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. - It entails mutations in chromosome that can be induced or naturally occurring. - Linkage analysis: a method in molecular genetics that is used to study people. Re- searchers using this method typically study families in which a disorder is heavily con- centrated. - Researchers in this area often hypothesize gene-environment interactions. This is the notion that a disorder or related symptoms are the joint product of a genetic vulnerability and specific environmental experiences or conditions. Neuroscience and Biochemistry in the Nervous System - Neuroscience is the study of the brain and the nervous system. - Each neuron has 4 major parts: - 1. The cell body - 2.several dendrites - 3. One or more axons of varying lengths (usually only one long and thin axon extending a considerable distance form the cell body) - 4. Terminal buttons on the many end branches of the axon - Nerve impulse: which is a charge in the electric potential of Th. Cell, travels down the axon to the terminal ending. - Between the terminal endings of the sending axon and cell membrane of the receiving neuron, thee is a small gap, called the synapse. - For a nerve impulse to pass from one neuron Th. Another and for communication to occur, the impulse must have a way of birding the synaptic gap. The terminal buttons of each axon contain synaptic vesicles, small strict that are filled with neurotransmitters, email substance that allow a nerve impulse to cross the synapse.
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