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Chapter 2

Psychology 46-355 Chapter 2 notes

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Chapter Two – page 1 AN INTEGRATIVE APPROACH TO PSYCHOPATHOLOGY I. One-Dimensional versus Multidimensional Models A. One-dimensional models posit single causes of psychopathology (e.g., its all conditioning, its all biology, its all social or psychological). B. Multi-dimensional models hold that a system of different reciprocal influences (i.e., biological, cognitive, learning, emotional, social, cultural) interact in complex ways to yield the major etiological and maintaining processes responsible for abnormal behavior. As such, any biological or environmental influence can become part of this system and cannot be considered in an isolated context. II. Genetic Contributions to Psychopathology A. The nature of genes 1. Genes are segments of deoxyribonucleic acid (DNA) that contain information about specific characteristics. 2. Each human cell contains 46 chromosomes (arranged in 23 pairs – half from each parent). 3. The first 22 pairs of chromosomes program development of body (including the brain) and the last pair, called the sex chromosomes, determines sex phenotype. 4. Dominant gene is one of the pair of genes that determine a particular trait and the effect can be quite noticeable. 5. Recessive gene must be paired with another recessive gene to determine a trait. 6. Defective gene results if something is wrong with respect to the ordering of DNA molecules on the double helix. 7. Genes seldom determine our physical development in any absolute way and the same is true for psychopathology. Much of human development and behavior is polygenic (i.e., influences by many genes that individually exert a tiny effect). Because of this, scientists look for patterns of influence across genes using a procedure called quantitative genetics. B. New developments in the study of genes and behavior 1. The best estimate for genetic contribution to enduring personality traits and cognitive abilities in humans is about 50%. 2. With respect to psychological disorders, genetic influences seem to account for less than half the etiological explanation; however, no individual genes have been identified relating to any major psychological disorders. 3. More important questions now are how genetic and environmental factors interact to influence psychological disorders. Chapter Two – page 2 C. The interaction of genetic and environmental effects 1. An example of gene-environment interaction was proposed by Eric Kandel, who stated that the process of learning may change the genetic structure of cells. This may occur when environmental processes turn on dormant genes and changes in the brain's biochemical functioning. This view lends support to the notion that we are less hardwired than previously thought. 2. The diathesis-stress model a. According to this model of gene-environment interaction, persons inherit from multiple genes tendencies to express certain traits or behaviors (diathesis), which may then be activated under certain environmental events such as stress. Examples include blood-injury-injection phobia and alcoholism. The diathesis or vulnerability does not necessarily lead to a disorder unless some specific life event occurs. b. A person with a large diathesis would, according to this model, require a smaller amount of stress for a disorder to develop compared to someone with a relatively smaller diathesis to begin with. 3. The Reciprocal gene-environment model a. This model states that persons are believed to have a genetically determined tendency to create the very environmental risk factors that trigger genetic vulnerabilities. b. Such a model may be used to explain depression, divorce, and personality characteristics such as impulsivity. 4. Nongenomic "inheritance" of behavior a. Related to research suggesting that there has been an overemphasis on the role of genetic influence on personality, temperament, and their contribution to the development of psychological disorders. Examples include research on genetically identical mice (including rats and rhesus monkeys using cross fostering strategies) reared in identical environments, but perform and behave quite differently on several experimental tasks above what genes would suggest. b. The moral is that it is even too simplistic to say that the genetic contributions to personality traits or psychopathology is 50%; one must consider the heritable contribution in the context of an individual’s past and present environment. Chapter Two – page 3 III. Neuroscience and its Contributions to Psychopathology A. The field of neuroscience focuses on understanding the role of the nervous system in disease and behavior. Knowing how the nervous system and particularly the brain works is central to understanding behavior, emotion, and cognitive processes. B. The central nervous system (CNS) 1. Consists of the brain and spinal cord and processes all information received from our sense organs and reacts as necessary. 2. Neurons control every thought and action, the brain contains an average of 140 billion neurons. (Worksheet) a. The typical neuron contains a central cell body with two different kinds of branches. One set of branches, dendrites, extend from the cell body to receive chemical messages from other nerve cells which are converted into electrical impulses. The other branch, the axon, transmits these impulses to other neurons. Any one nerve cell is linked with multiple others. b. Neurons themselves operate electrically, but communicate with other neurons chemically. The synaptic cleft (or gap) is a small space that exists between the axon of one neuron and the dendrites of another. It is here where neurons communicate with one another via release of neurotransmitters. c. Neurotransmitters (page 42) are the chemicals released from one nerve cell to another across the synaptic cleft. After a neurotransmitter is released it is quickly drawn back from the synaptic cleft into the same neuron via a process known as reuptake. Major neurotransmitters implicated in psychopathology include norepinephrine (or noradrenaline), serotonin, dopamine, and gamma aminobutyric acid (GABA). (Brain worksheet) Chapter Two – page 4 3. The brain is divided into two parts. The lower brain stem is the most primitive part and is responsible for most of the automatic functions necessary for survival (e.g., breathing, sleeping, moving). The more advanced brain systems are located in the forebrain. a. The hindbrain is the lowest part of the brainstem, and contains the medulla, pons, and cerebellum (motor coordination). These structures control activities such as breathing, heartbeat, and digestion. b. The midbrain coordinates movement with sensory input and contains parts of the reticular activating system (RAS). The RAS contributes to arousal, tension, and waking and sleeping. c. At the very top of the brain stem (i.e., above the hindbrain) lies the diencephalon, which contains the thalamus and hypothalamus; these structures help transmit information to the forebrain and are integral to behavior and emotion. d. At the very base of the forebrain (just above the thalamus and hypothalamus) is the telencephalon, containing the limbic system. Limbic means "border," and this system figures prominently in much of psychopathology. It includes the following structures: hippocampus (sea horse), cingulate gyrus (girdle), septum (partition), and amygdala (almond). Emotional expression, impulse control, sex, aggression, hunger, and thirst are controlled by this part of the brain. Another area at the base of the forebrain is the basal ganglia, including the caudate (tailed) nucleus. Motor behavior is controlled by this area, and damage can cause twitching or shaking. e. The largest part of the forebrain is the cerebral cortex which contains over 80% of the neurons in the CNS. Reasoning and creative skills are derived from this brain area. The cerebral cortex is divided into two near-symmetrical hemispheres: the left hemisphere appears to be responsible for verbal and cognitive processes, whereas the right hemisphere appears more responsible for spatial abilities. f. Each hemisphere of the cerebral cortex consists of four separate areas of lobes. The temporal lobe is associated with the recognition of sights and sounds and long-term memory storage. The parietal lobe is associated with touch recognition. The occipital lobe integrates visual input. The frontal lobe is most interesting from the standpoint of psychopathology and is largely responsible for thinking and reasoning abilities, memory; it enables one to relate to people and events in the world and to behave as social animals. Chapter Two – page 5 C. The peripheral nervous system works in coordination with the brain stem to ensure proper bodily functioning and consists of the (1) somatic nervous system, which controls muscles and movement, and (2) autonomic nervous system (ANS), which is divided into the sympathetic and parasympathetic nervous systems. The ANS regulates the cardiovascular system, endocrine system (e.g., pituitary, adrenal, thyroid, gonadal glands) and aids in digestion and regulation of body temperature. 1. The sympathetic and parasympathetic branches of the ANS operate in a complementary fashion. The sympathetic nervous system mobilizes the body (e.g., increases heart rate) during periods of stress or danger and is part of the emergency or alarm response; the parasympathetic nervous system renormalizes arousal and facilitates digestion. 2. The endocrine system produces its own chemical messengers (i.e., hormones) and releases them directly into the bloodstream. Adrenal glands produce epinephrine (also called adrenaline) in response to stress, including salt-regulating hormones; the thyroid produces thyroxine, which facilitates energy metabolism and growth; the pituitary is the master gland that produces several regulatory hormones; and the gonads produce sex hormones (e.g., testosterone and estrogen). The endocrine system is closely related to the immune system and is implicated in anxiety, stress-related, and sexual disorders. 3. The hypothalamic-pituitary-adrenalcortical axis (HYPAC axis) illustrates the connection between the nervous and endocrine systems and is implicated in several forms of psychopathology. D. Neurotransmitters 1. Drug therapies function by either increasing or decreasing the flow of specific neurotransmitters. Agonists increase the activity of a neurotransmitter by mimicking its effects. Some drugs, known as antagonists, function to inhibit or block the production of neurotransmitter or function indirectly to prevent the chemical from reaching the next neuron by closing or occupying the receptors; other drugs increase production of competing biochemicals that deactivate the neurotransmitter or produce effects opposite those produced by the neurotransmitter (inverse agonists). Most drugs are either agnostic or antagonistic. 2. Types of neurotransmitters include: a. Serotonin (5HT) is concentrated in the midbrain and connected to the cortex, thus producing widespread effects on behavior, mood, and thought processes. Extremely low levels of serotonin are associated with less inhibition, instability, impulsivity, and tendencies to overreact to situations (e.g., aggression, suicide, impulsive overeating, excessive sexual behavior. Tricyclic antidepressants (e.g., imipramine), and new classes of serotonin specific reuptake inhibitors (SSRIs; e.g., Prozac) affect the serotonergic system (see also St. John’s- wort). Chapter Two – page 6 b
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