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Chapter 2

PSYB32_Chapter 2

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University of Toronto Scarborough
Konstantine Zakzanis

Chapter 2-Current Paradigms and the Role of Cultural Factors The Role of Paradigms A paradigm is a set of basic assumptions that outline the particular universe of scientific inquiry (a conceptual framework) They specify what problems scientists will investigate and how they will go about this investigation It injects particular biases into definitions and collection of data The Biological Paradigm The biological paradigm of abnormal behaviour is a continuation of the somotgenic hypothesis. Holds that mental disorders are caused by biological processes. Often referred to as the medical model, or disease model For a time the germ theory was the paradigm of medicine, but it soon became evident that this theory could not account for all diseases Hall believed the removal of the ovarian cysts was a treatment for melancholia, mania, and delusions Contemporary Approaches to the Biological Paradigm There are three areas within the biological paradigm: Behaviour genetics, molecular genetics, and biochemistry Behaviour Genetics Each chromosome is made up of thousands of genesthe carrier for genetic info Behaviour genetics is the study of individual differences in behaviour that are attributable (in part) to individual differences in genetics The total genetic makeup is the genotype The phenotype is the observable behavioural characteristics The phenotype changes over time and is viewed as the product of the genotype and the environment Various clinical disorders are disorders of the phenotype A predisposition (known as a diathesis) may be inherited but not the disorder itself Weather the genotype will become a phenotypic disorder depends on environment and experience The study of behaviour genetics has relied on four basic methods to uncover wether a predisposition for a psychopathology is inherited: comparison of family, twins, investigation of adoptees, and linkage analysis Family method used to study genetic predisposition of members of a family On average siblings as well as parents and their children are identical in 50% of their genetic backgroundknown as first-degree relatives Nephews and nieces share 25% of the genetic makeup of an uncleknown as second- degree relatives The starting point of these investigations is a collection of people with the diagnosis in question known as index cases or probands If a genetic predisposition for the disorder being studied is present then the first degree relatives of the index cases should have the disorder at a higher rate than the general population In the twin method, both monozygotic twins (MZ) and dizygotic twins (DZ) are compared When twins are similar diagnostically they are said to be concordant To the extent that a predisposition for a disorder can be inherited, concordance for the disorder should be greater in the genetically identical MZ pairs Twin studies depends on equal environment assumptionenvironmental factors that are partial causes for concordance are equally influential for both MZ and DZ pairs (ex. Equal number of stressful experiences) The adoptees method studies children who were adopted and reared apart from their parents with abnormal disorders. It eliminates the effects of being reared by disordered parents If a high frequency of children reared apart from parents who have a disorder have a disorder as well then there would be a genetic predisposition for the disorder Molecular Genetics Tries to specify the genes or genes involved Allele refers to any one of several dNA codings that occupy the same position on a chromosome. Genotype=set of alleles Genetic polymorphism refers to variability among members of the same species It involves differences in DNA sequences Linkage analysis is a method in molecular genetics used to study people Researches study blood samples from families in which a disorder is heavily concentrated and study the inherited pattern of characteristics whose genetics are fully understoodgenetic markers If the occurrence of a psychopathology goes along with the occurrence of a genetic marker than it is concluded that the gene predisposing individuals for the psychopathology is located near the gene for the other characteristic (genetic marker) Gene environment interactionsthe notion that a disorder or related symptoms are the joint product of genetic vulnerability and environmental experiences Neuroscience and Biochemistry in the Nervous System Each neuron has four major parts: o Cell body o Dendrites o One or more axons o Terminal buttons on end branches of axons When a neuron is stimulated at the cell body/dendrites it sends a nerve impulsea change in electric potential of the cell Between the terminal buttons of the sending neuron and the membrane of the receiving neuron there is a small gap known as a synapse The terminal buttons contain structures that have neurotransmitterschemical substances that allow a nerve impulse to cross the synapse The cell membrane of the postsynaptic cell contains receptor sites that are configures so specific neurotransmitters can fit A message is sent to the postsynaptic neuron which can be excitory or inhibitory Some remaining neurotransmitter is broken down by enzymes and some is pumped back to presynaptic cell via reuptake Norepinephrine is a neurotransmitter of the sympathetic nervous system and is involved in producing high levels of arousal, thus it may be involved in anxiety disorders Serotonin may be involved in depression and dopamine in schizophrenia. GABA inhibits some nerve impulses and may be involved in anxiety disorders The onset of puberty in adolescents results in a decrease in serotonin and a decrease in dopamine activity contributing to a increased risk for psychopathology during adolescence A given disorder is caused by too much or too little of a particular neurotransmitter This could result from an error in the metabolic steps in the synthesis of a neurotransmitter A disturbance in the amount of a neurotransmitter can also occur when there is a failure in reuptake leaving excess neurotransmitter molecules in the synapse Some receptors are too numerous or too easily excited producing psychopathology (Ex. There is an over-abundance of dopamine receptors in people with schizophrenia) Structure and Function of The Human Brain Brain is enveloped in three membranes known as meninges Is divided into two cerebral hemispheres. Cerebrum is thinking center of brain Major connection between hemispheres is called corpus callosum 6 layers of neuron bodies form the cerebral cortex Cortex contains ridges (gyri) and fissures (sulci) Frontal lobe lies in front of the central sulcus o Left Brocas Area Learning o Right Retrieval of Info Responsible for Manic-like symptoms Parietal lobe is behind it and above the lateral sulcus o Left Visual spatial abilities Temporal lobe is below the lateral sulcus o Left Verbal comprehension o Right Nonverbal comprehension Occipital lobe is behind temporal and parietal Initiation of movements is in the band in front of the central sulcus Sensations is in the band behind the central sulcus Left hemisphere controls speech and analytical thinking Right hemisphere controls spatial relations and emotion Interior of the brain is composed of white matter (bundles of myelin shealths) Centers lower in the brain that are pockets of grey matter known as nuclei Four masses deep within each hemisphere are called basal ganglia There are also cavities called ventricles Diencephalon contains o Thalamusrelay station for all sensory pathways (except olfactory) o Hypothalamusintegrates all primitive processes (ex. Persipiration) The midbrain is a mass of nerve fibre that connects the cerebral cortex with the pons, medulla, cerebellum, and spinal cord Brain stem is a relay station and contains o Ponsconnect cerebellum with spinal cord o Medulla oblongatamain line of traffic for zones ascending from spinal cord and descending from brain. (Ex. Autonomic nervous systemheartbeat etc.)
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