Chapter 17 - Chapter 17 Chapter 17 Anxiety Disorders,...

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Unformatted text preview: Chapter 17 Chapter 17 Anxiety Disorders, Autistic Disorder, ADHD, and Stress Disorders Anxiety Disorders Anxiety Disorders A psychological disorder characterized by tension, overactivity of the ANS, expectation of an impending disaster, and continuous vigilance for danger Two types of anxiety disorders that appear to have biological causes: – Panic disorder – Obsessive­compulsive disorder (OCD) Anxiety Disorders Anxiety Disorders Panic disorder – Characterized by episodic periods of symptoms such as shortness of breath, irregularities in heartbeat, and other autonomic symptoms, accompanied by intense fear – Onset in young adulthood – Victim often feels that he or she is going to die – Between panic attacks, people with panic disorder suffer from anticipatory anxiety, the fear that another panic attack will strike – Anticipatory anxiety often leads to agoraphobia, fear of being away from home or other protected places – Disorder appears to be hereditary – Strange genetic association between “loose joints” and panic disorder Patients with joint hypermobility syndrome are more likely to also have panic disorder than control subjects Anxiety Disorders Anxiety Disorders Panic disorder – Previously treated with a combo of behavior therapy and a benzodiazepine (which have strong anxiolytic, or anxiety reducing, effects) Benzodiazepine receptors are located on the GABAA receptor complex When benzo binds with receptor, it increases the sensitivity of the GABA binding site and produces an anxiolytic effect Anxiety disorders may be caused by decreased number of benzo receptors – SSRI’s used to treat panic disorder and OCD – Cingulate, prefrontal, and anterior temporal cortices are involved (esp. decrease in activity during panic attacks) Anxiety Disorders Anxiety Disorders Obsessive compulsive disorder (OCD) – Suffer from obsessions (an unwanted thought or idea with which a person is preoccupied) and compulsions (the feeling that one is obliged to perform a behavior, even if one prefers not to do so) – Incidence is 1­2% of population; females > males; most commonly begins in young adulthood – Compulsions fall into 4 categories: counting, checking, cleaning, avoidance – Some investigators believe that the compulsive behaviors are forms of species­typical behaviors (e.g. grooming, cleaning, and attention to sources of potential danger) that are released from normal control mechanisms by a brain dysfunction – Could also be pathological examples of social rituals Anxiety Disorders Anxiety Disorders OCD (con’t) – May have genetic origin – OCD is associated with Tourette’s syndrome (a neurological disorder characterized by tics and involuntary vocalizations and sometimes by compulsive uttering of obscenities and repetitions of the utterances of others) that appears in childhood Treatment for Tourette’s includes antischizophrenic meds that block DA D2 receptors – Many patients that have OCD have tics, and many patients with Tourette’s have obsessions and compulsions – Both disorders may be produced by the same genotype – However, some brain damage (esp. to basal ganglia, cingulate gyrus, and prefrontal cortex) may lead to development of OCD Anxiety Disorders Anxiety Disorders OCD (con’t) – Tic disorders ca be caused by a streptococcal infection, that can damage brain tissue Esp. by damage to basal ganglia – Increased activity in frontal lobes and caudate nucleus in patients with OCD – Some patients with severe OCD have been treated with cingulotomy (surgical destruction of the cingulum bundle, which connects the prefrontal cortex with the limbic system) Helps reduce intense anxiety and the symptoms of OCD – Direct pathway (excitatory) in basal ganglia – symptoms of OCD may be a result of overactivity in this pathway – Most effective therapy for OCD is drug therapy All 5­HT reuptake blockers Autistic disorder Autistic disorder 4 in every 10,000 infants born with this disorder A chronic disorder whose symptoms include failure to develop normal social relations with other people, impaired development of communicative ability, lack of imaginative ability, and repetitive, stereotyped movements Afflicts boys 3x more than girls Most autistic people are mentally retarded, but not all are Autistic disorder is one of several pervasive developmental disorders that have similar symptoms – Asperger’s syndrome – less severe, do not include language impairment or cognitive deficits – Rett’s disorder – genetic disorder seen in girls; accompanies and arrest of normal brain development during infancy – Childhood disintegrative disorder – show normal social and intellectual develop. until begin to regress sometime b/t ages 2­ 10 yrs. Autistic disorder Autistic disorder Autism includes affective, cognitive and behavioral abnormalities Some investigators suggest that this may stem from brain abnormalities that prevent the person from forming a “Theory of mind” (i.e. unable to predict and explain the behavior of other humans in terms of their mental states) Imaging studies show great decrease in activity of fusiform face area (region of brain responsible for face recognition) in autistic individuals while looking at pictures of faces Autistic disorder Autistic disorder Possible causes – Heritability Some forms appear to be heritable 2­3% of siblings of autistic people also have autism Concordance rate for monozygotic twins is ~70% May be associated with specific genetic disorders: Phenylketonuria (PKU) – caused by inherited lack of an enzyme that converts phenylalanine (amino acid in diet) into tyrosine; buildup of phenylalanine can cause disruption in brain development, and sometimes autism – Brain pathology ~20% of all cases of autism have definable biological causes, such as rubella, prenatal thalidomide, encephalitis, etc. Can result from a wide variety of factors that damage the brain or impair its development Thalidomide (a drug given to pregnant women in 1960s to treat morning sickness) caused serious birth defects Attention­Deficit/Hyperactivity Attention­Deficit/Hyperactivity Disorder (ADHD) A disorder characterized by uninhibited responses, lack of sustained attention, and hyperactivity First shows itself in childhood Usually discovered at school DSMIV requires the presence of 6 or more of 9 symptoms to diagnose – e.g. difficulty in sustaining attention in tasks of play activities; easily distracted by extraneous stimuli Diagnosis is often difficult Most common treatment is methylphenidate (Ritalin), which inhibits reuptake of DA Attention­Deficit/Hyperactivity Attention­Deficit/Hyperactivity Disorder (ADHD) Possible causes – Strong evidence for hereditary factors in a person’s likelihood of developing ADHD – Symptoms may be a result of a “delay of reinforcement gradient” (i.e. the longer the delay of some type of reinforcement for a behavior, the less effective that reinforcement is) – May be caused by underactivity of DA transmission Results from human and animal studies contradict each other; not clear whether ADHD is caused by excessive number of DA transporters – Imaging studies showed decreased blood volume in basal ganglia and cerebellar vermis of boys with ADHD Stress Disorders Stress Disorders Stress – a general, imprecise term that can refer either to a stress response or to a stressor – Stressor – a stimulus (or situation) that produces a stress response – Stress response – a physiological reaction caused by the perception of aversive or threatening situations The physiological responses that accompany the neg. emotions prepare us to threaten rivals or fight them or to run away – Fight­or­flight response – a species­typical response preparatory to fighting or fleeing; thought to be responsible for sme of the deleterious effects of stressful situations on health Stress Disorders Stress Disorders Physiology of the stress response – Autonomic and endocrine responses to emotions: sympathetic branch of ANS becomes active, and adrenal glands secrete epinephrine, NE and steroid stress hormones – Epinephrine affects glucose metabolism, causing nutrients stored in muscles to become available to provide energy for strenuous exercise – Some of the behavioral and physiological responses produced by aversive stimuli appear to be mediated by NE neurons – The other stress­related hormone is cortisol, a glucocorticoid (a hormone that has effects on metabolism) secreted by the adrenal cortex – Secretion of glucocorticoids is controlled by paraventricular nucleus of the hypothalamus (PVN) The neurons of the PVN secrete a peptide called corticotropin­releasing hormone (CRH) which stimulates the anterior pituitary to secrete adrenocorticotropic hormone (ACTH), which enters the bloodstream and stimulates the adrenal cortex to secrete glucocorticoids Stress Disorders Stress Disorders Health effects of long­term stress – Many studies of humans who have been subjected to stressful situations have found evidence of ill health – Hans Selye, a pioneer in the study of stress, suggested that most of these harmful effects from stress were produced by prolonged secretion of glucocorticoids Effects include increased blood pressure, damage to muscle tissue, steroid diabetes, etc. Research with animals shows that long­term exposure to glucocorticoids destroys neurons in field CA1 of hippocampus, affecting memory in the long­term Severe stress appears to cause brain damage in humans as well Stress Disorders Stress Disorders Posttraumatic Stress Disorder (PTSD) – A psychological disorder caused by exposure to a situation of extreme danger and stress – Symptoms include recurrent dreams or recollections – Can interfere with social activities and cause a feeling of hopelessness – Genetic factors play a role in a person’s susceptibility to develop PTSD and to be involved in an event that may cause PTSD – Found hippocampal damage in patients with PTSD – However, found lower levels of cortisol, instead of assumed higher levels (in order to cause brain damage) Exposure to stress increases the number and sensitivity of glucocorticoid receptors in the hypothalamus and anterior pituitary Instead, high levels of CRH may play a role in the development of PTSD Stress Disorders Stress Disorders Stress and cardiovascular disease – The degree to which people react to potential stressors may affect the likelihood that they will suffer from cardiovascular disease – Individuals who had hyperreacted to a stress test earlier in life were more likely to have high blood pressure later in life – Studies with monkeys demonstrate that individual differences in emotional reactivity are a risk factor for cardiovascular disease The animals that showed strongest negative reactions to a threat eventually developed higher rates of coronary artery disease – Acute stress can also affect cardiovascular disease Can cause constriction of coronary arteries, arrhythmias in heartbeat, stimulation of platelet function (causes forming of clots), and increased viscosity of the blood Stress Disorders Stress Disorders The coping response – One of the most important variables that determines whether an aversive stimuli will cause a stress reaction is the degree to which the stimulus can be controlled – Animals can learn coping responses in order to avoid aversive stimuli, and thus reduce their stress response – The opportunity to make a coping response decreases the negative impact of stress on the hippocmpus Stress Disorders Stress Disorders Psychoneuroimmunology – Stress response can impair the function of the immune system – Study of interactions b/t the immune system and behavior is called psychoneuroimmunology – The immune system Function is to protect us from infection 2 types of reactions occur when the body is invaded by foreign organisms: – Chemically mediated: involves antibodies (proteins produced to seek out and destroy antigens present on invading organisms) One type of antibody is released into circulation by B­lymphocytes, which develop in bone marrow; the antibodies released are called immunoglobulins, which are chains of proteins that help destroy invading microorganisms – Cell mediated: produced by T­lymphocytes, white blood cells that originate in thymus gland – Communication b/t cells is accomplished by cytokines Stress Disorders Stress Disorders Psychoneuroimmunology – Neural control of the immune system Stress increases the secretion of glucocorticoids, and these hormones directly suppress the activity of the immune system Individuals with severe stress showed lowered levels of antibodies This suppression is largely mediated by glucocorticoids, which are mediated by neural activity – Stress and infectious disease Stress­producing events can increase a person’s susceptibility to illness Since the immune system is suppressed, a person is more likely to develop an illness after times of stress ...
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This note was uploaded on 07/31/2011 for the course PSB 3004 taught by Professor Williams during the Spring '08 term at University of Florida.

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