Chapter 22 Stress Mosby items and derived items
Chapter 22: Stress Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 1
SELYE’S CONCEPT OF STRESS Development of the stress concept Ø Through many experiments, Selye exposed animals to noxious agents and found that they all responded with the same syndrome of changes, or “stress triad” Definitions Stress: a state or condition of the body produced by “diverse nocuous agents” and manifested by a syndrome of changes Ø Stressors: agents that produce stress Ø General adaptation syndrome: group of changes that manifest the presence of stress Ø Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 2
SELYE’S CONCEPT OF STRESS (cont. ) Stressors are extreme stimuli—too much or too little of almost anything Ø Stressors are often injurious or painful stimuli Ø Anything an individual perceives as a threat is a stressor for that individual Ø Stressors are different for different individuals and different for one individual at different times Ø General adaptation syndrome Manifestations: stress triad (hypertrophied adrenals, atrophied thymus and lymph nodes, and bleeding ulcers); many other changes Ø Stages: three successive phases: alarm reaction, stage of adaptation or resistance, and stage of exhaustion; each is characterized by a different syndrome of changes (Table 22 -1) Ø Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 3
SELYE’S CONCEPT OF STRESS (cont. ) Mechanism of stress Consists of a group of responses (syndrome) to internal condition of stress; stress responses are nonspecific: the same syndrome of responses occurs regardless of kind of extreme change that produced stress Ø Stimulus that produces stress and thereby activates stress mechanism is nonspecific; it can be any kind of extreme change in the environment Ø Stress responses, Selye believed, were adaptive, tend to enable the body to adapt to and survive extreme change; Selye referred to this syndrome of stress responses as general adaptation syndrome Ø Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 4
SELYE’S CONCEPT OF STRESS (cont. ) Numerous factors influence stress responses: individual’s physical and mental condition, age, sex, socioeconomic status, heredity, and previous experience with similar stressors Ø Successfully coping with stress occurs most often; results in adaptation, healthy survival, and increased resistance; sometimes, however, stress produces exhaustion or death Ø Summary of Selye’s stress mechanism (Figure 22 -4, then Figures 22 -2 and 22 -3) Ø Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 5
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SOME CURRENT CONCEPTS ABOUT STRESS Definitions Stress: any stimulus that directly or indirectly stimulates the hypothalamus to release corticotropin-releasing hormone Ø Stress syndrome: also called the stress response; many diverse changes initiated by stress Ø Stress syndrome (Figure 22 -6) Stress and disease: Selye held that stress could result in disease instead of adaptation Indicators of stress Changes caused by increased sympathetic activity (e. g. , faster, stronger heartbeat; higher blood pressure; sweaty palms; dilated pupils) Ø Changes resulting from increased corticoids: eosinopenia, lymphocytopenia, increased adrenocorticoids in blood and urine Ø Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 9
Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 10
SOME CURRENT CONCEPTS ABOUT STRESS (cont. ) Corticoids and resistance to stress Ø Still controversial; not proved that increased corticoids increase an animal’s or a person’s ability to resist stress, but corticoid levels in blood do increase during stress Psychological stressors: anything that an individual perceives as a threat to survival or self-image (Figure 22 -7) Ø Psychological stress: a mental state characterized by a syndrome of subjective and objective responses; dominant subjective response is anxiety; some characteristic objective responses are restlessness, irritability, lying, crying Ø Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 11
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SOME CURRENT CONCEPTS ABOUT STRESS (cont. ) Effects of intrauterine stress Ø Fetus develops short- and long-term responses to stress experienced during intrauterine development (Figure 228) • Frequent stressors include maternal malnutrition, hypoxia, and exposure to toxins such as alcohol • Low birth weight and preterm delivery are common immediate responses to intrauterine stress Ø Maternal-fetal blood levels of cortisol are important mediators of stress • Influenced by endocrine secretory activity of maternalfetoplacental unit and the shared maternal-fetal hypothalamic-pituitary-adrenal mechanism Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 13
SOME CURRENT CONCEPTS ABOUT STRESS (cont. ) Effects of intrauterine stress (cont. ) Ø Fetal programming responses to stress often result in negative outcomes later in life • Affect many organ systems and even life expectancy Ø Concept of “biological tradeoffs” may be involved in fetal programming outcomes; for example, low birth weight and preterm delivery may be tradeoffs by fetus to survive the stress of maternal malnutrition in a problem pregnancy Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 14
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THE BIG PICTURE: STRESS AND THE WHOLE BODY Stress affects the entire body Nervous system detects and integrates stressors that trigger stress responses Stress affects immune system Ø Neuroimmunology studies mind-immunity link Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc. , an affiliate of Elsevier Inc. 16
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