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ch.2 for PSYB32

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University of Toronto Scarborough
Konstantine Zakzanis

Chapter 2 Twin Method: both monozygotic twins (identical; develop from a single fertilized egg; same sex) and dizygotic twins (fraternal; develop from separate eggs and are on average only 50% alike genetically; can be same sex or opposite) are compared Diagnosed cases compared to other twin to see presence of disorder When twins are similar diagnostically they are said to be concordant; concordance for disorder should be greater in MZ pairs than DZ pairs if this happens than disorder said to be heritable For child to get the disorder that the parents have, there doesnt have to be a genetic predisposition it may run in families only because of the environment the child was raised Equal environment assumption: environmental factors that are partial causes of concordance are equally influential for MZ pairs and DZ pairs; assumption only applies to factors that are plausible environmental causes of psychopathology; this assumption asserts that MZ pairs and DZ pairs have equivalent number of stressful life experiences 3 factors as biasing heritability estimates: violation of the equal environments assumption, sex of the participants and his or her age when the assessment took place o Only environmental factors contributed to exposure to events involving non-assaultive traumas o Both genetic and environmental factors contributed to exposure to assaultive traumas o Therefore, genetic factors may determine the extent to which a person is likely to experience post-traumatic stress after an assaultive trauma Adoptees Method: study children who were adopted and reared apart of their parents with abnormal disorders If there is a high frequency of panic disorders found in children reared apart from parents who also had panic disorders, then there would be support for the theory that genetic predisposition figures in the disorder [Molecular Genetics] Tries to specify the particular gene or genes involves and the precise functions of these genes Each cell consists of 46 chromosomes with thousands of genes per chromosome (our genetic material) Allele: refers to any one of the several DNA coding that occupy the same position or location on a chromosome: genotype is his or her set of alleles Genetic polymorphism: refers to variability among members of the species; involves differences in the DNA sequence that can manifest in very different forms among members in the same habitat; entails mutations in a chromosome that can be induced or naturally occurring Linkage analysis: method in molecular genetics that is used to study people; researches use it to study families in which a disorder is heavily concentrated; they collect diagnostic info and blood samples from affected individuals and their relatives and use the blood samples to study the inheritance pattern of characteristics whose genetics are fully understood (genetic markers) If occurrence of a form of psychopathology among relatives goes along wit 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 in a similar location on that chromosome (i.e. it is linked) as the gene controlling the other characteristic Linkage analysis: mood disorders, OCD and schizophrenia Gene-environment interactions: notion that a disorder or related symptoms are joint product of a genetic vulnerability and specific environmental experiences or conditions [Neuroscience and Biochemistry in the nervous system] Neurons have 4 major parts: cell body, several dendrites (short and think extensions), one or more axons of varying lengths (usually only one long and thin axon extending considerable distance from the cell body) and a terminal buttons on the many end braches of the axon Nerve impulse: change in electric potential of the cell o When neuron is stimulated at its cell body or dendrites a nerve impulse travels down the axon to the terminal ending. Between the terminal ending and cell membrane of receiving neuron is a small gap called the synapse o Terminal buton of each axon contains synaptic vesicles (small structures that allow a nerve NT); NT are chemical substances that allow a nerve impulse to cross the synapse www.notesolution.com o Nerve impulses cause the synaptic vesicles to release molecules of their transmitter substances and these molecules flood the synapse and diffuse toward the receiving or postsynaptic neuron cell membrane of the postsynaptic cell contains proteins (receptor sites) that are configured so that specific NT can fit into them when NT fit into receptor site a msg can be sent to postsynaptic cell o What happens to postsynaptic neuron depends on its integrating thousands of similar msgs Sometimes msgs are excitatory: leading to the creation of nerve impulse in the postsynaptic cell Msgs is inhibitory: making postsynaptic less likely to fire nerve impulse Returning back to normal state: o Not all released NT has found its way to postsynaptic receptors- some broken down by enzymes and some pumped back into the presynaptic cell through a process of reuptake Norepinephrine: NT of the peripheral sympathetic nervous system is involved in producing states of high arousal and therefore may be involved in anxiety disorders Serotonin and dopamine are NT in the brain; serotonin involved in depression and dopamine in schizophrenia GABA: inhibits some nerve impulses and may be involved in anxiety disorders Maturational changes influence NT levels o Onset of puberty results in decrease in serotonin and a decrease in dopamine activity in certain cortical areas Disorder is caused y either too much or too little of a particular transmitter (i.e. mania- too much norepinephrine; anxiety disorder- too little GABA) Synthesis of NT (series of metabolic steps): amino acids enzymes catalyzes each reaction o Too much or little of NT results form error in one of the metabolic pathways or from alterations in usual processes by which transmitters deactivated after being released into the synapse (i.e. reuptake) Failure to pump leftover NT back into presynaptic cell and then new nerve impulse causes further NT to be released into synapse therefore postsynaptic cell has double the dose of NT therefore more likely to fire a nerve impulse Receptors are also a cause of psychopathologies o If receptor on postsynaptic neuron were too numerous or too easily excited the result would be akin to having too much transmitter released therefore more sites available with which the NT could interact, increasing the changes of the postsynaptic neuron would be stimulated Delusions and hallucinations of schizophrenia may result from an over abundance of dopamine receptors [Biological Approaches to Treatment] Prevention or treatment of mental disorders should be possible by altering bodily functioning; biological defect biological intervention Use of Psychoactive drugs increasing; o tranquilizers (valium) effective in reducing tension associated with some anxiety disorders by stimulating GABA neurons to inhibit other neural systems that create the physical symptoms of anxiety o antidepressants (Prozac) increase neural transmission in neurons that use serotonin as a NT by inhibiting reuptake of serotonin o antipsychotic drug (Clozaril) used for treatment of schizophrenia; reduces the activity of neurons that use dopamine as NT by blocking their receptors o stimulants (Ritalin) used to treat children with attention deficit and hyperactivity disorder; these increase levels of several NT that help children pay attention drugs can act efficiently and often provide symptomatic improvement relatively quickly o serotonin reuptake inhibitors described as having delayed onset; helps to treat depression contemporary approaches to biological assessment: involves attempts to make inferences about the functioning of the nervous system (neuropsychological assessment) or to see the actual structure and functioning of the brain and other parts of the nervous system (MRI) clinical scientist can believe in biological basis of mental problem but can recommend psychological intervention effects of cognitive-behavioural theory (CBT) on OCD showed decreased metabolism in the right caudate nucleus whereas, CBT in phobia resulted in decreased activity in limbic and paralimbic areas different effects for different types of interventions [Evaluating the Biological Paradigm] www.notesolution.com
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