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Chapter Six.docx

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PSYC 3140
Joel Goldberg

Chapter SixStress means experiencing events that we perceive as endangering our physical or psychological well being These events are usually referred to as STRESSORS and peoples reaction to them are labeled STRESS RESPONSES Any negative event is perceived as more stressful if it is uncontrollableGalvanic Skin Response GSR a drop in the electrical resistance of the skin which is an index of psychological arousal Unpredictability also makes some events especially stressfulWith unpredictable events people feel they can never relax because the events may occur at any time so they remain anxious all the time This explanation has been called the SAFETY SIGNAL HYPOTHESISAny change in life that requires numerous readjustmentseven a positive changecan be perceived as stressful For example most people think of marriage as a positive event but it requires many readjustments in daily life and selfconcept as two people go from living as single individuals to living as lifetime partnersPsychological Responses To Stress The body mobilizes to handle the stressorThe liver releases extra sugar glucose to fuel our muscles and hormones are released to stimulate the conversion of fats and proteins to sugarThe bodys metabolism increases in preparation for expending energy on physical actionHeart rate blood pressure and breathing rate increase and muscles tenseAt the same time less essential activities such as digestion are curtailedSaliva and muscle dry up increasing the size of the air passages to the lungsThe bodys natural pain killers endorphins are secreted and the surface blood vessels constrict to reduce bleeding in case of injuryThe spleen releases more red blood cells to help carry oxygenMost of these psychological changes result from the activation of two systems controlled by the hypothalamus The AUTONOMIC NERVOUS SYSTEM in particular the sympathetic division of this system and the ADRENALCORTICAL SYSTEM a hormonereleasing systemThese physiological responses have developed through evolution to prepare the body to fight a threat or to flee from itto attack a sabertoothed tiger or to run away from itand have been labeled the FIGHTORFLIGHT RESPONSEThe sympathetic system acts directly on the smooth muscles and internal organs to produce some of the bodily changesfor example increased heart rate and elevated blood pressureThe sympathetic system also stimulates the release of a number of hormones including epinephrine adrenaline and norepinephrine which perpetuate a state of physiological arousalThe hypothalamus activates the adrenalcortical system by releasing corticotrophinrelease factor CRF which signals the pituitary gland to secrete adrenocorticotropic hormone ACTH the bodys major stress hormoneACTH stimulates the outer layer of the adrenal glands the adrenal cortex resulting in the release of a group of hormones the major one being CORTISOLThe amount of cortisol in blood or urine samples is often used as a measure of stressACTH also signals the adrenal glands to release about 30 other hormones each of which plays a role in the bodys adjustment to emergency situationsEventually the hormones signal the hippocampus a part of the brain that helps regulate emotions to turn off this physiological cascade when the threatening stimulus has passedWhen a stressor is chronic and a person or an animal cannot fight it or flee from it the chronic physiological arousal that results can be severely damaging to the body
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