Hockenbury Discovering Psychology 5th txtbk

Physical Effects of Stress505Pathway 1: Acute stressPathway 2: Prolonged stressHypothalamusHypothalamusSympatheticnervoussystemAdrenalmedullaPituitaryACTHreleaseAdrenalcortexFigure 12.3 Endocrine SystemPathways in Stress Two differentendocrine system pathwaysare involved in the response tostress (Joëls & Baram, 2009;Lupien & others, 2009). WalterCannon identified the endo crinepathway shown on the left sideof this diagram. This is the pathwayinvolved in the fight-orflightresponse to immediatethreats. Hans Selye identified theendocrine pathway shown onthe right. This second endocrinepathway plays an important rolein dealing with prolonged, orchronic, stressors.Secretion of catecholamines:• Increases respiration• Increases heart rate• Increases blood pressure• Increases blood flow to the muscles• Digestion is inhibited• Pupils dilateSecretion of corticosteroids:• Increases release ofstored energy• Reduces inflammation• Reduces immune systemresponseWithout question, the fight-or-flight response is very useful if you’re suddenly facedwith a life-threatening situation, such as a guy pointing a gun at you in a desertedparking lot. However, when exposure to an unavoidable threat is prolonged, the intensearousal of the fight-or-flight response can also become prolonged. Under theseconditions, Cannon believed, the fight-or-flight response could prove harmful tophysical health.Hans SelyeStress and the General Adaptation SyndromeCannon’s suggestion that prolonged stress could be physically harmful was confirmedby Canadian endocrinologist Hans Selye. Most of Selye’s pioneering researchwas done with rats that were exposed to prolonged stressors, such as electric shock,extreme heat or cold, or forced exercise. Regardless of the condition that Selye usedto produce prolonged stress, he found the same pattern of physical changes in therats. First, the adrenal glands became enlarged. Second, stomach ulcers and loss ofweight occurred. And third, there was shrinkage of the thymus gland and lymphglands, two key components of the immunesystem. Selye believed that these distinctphysical changes represented the essentialeffects of stress—the body’s response to anydemand placed on it.Selye discovered that if the bodily “wearand tear” of the stress- producing eventcontinued, the effects became evident inthree progressive stages. He called thesestages the general adaptation syndrome.During the initial alarm stage, intensearousal occurs as the body mobilizes internalphysical resources to meet the demandsfight-or-flight responseA rapidly occurring chain of internal physicalreactions that prepare people either to fightor take flight from an immediate threat.catecholamines(cat-eh-COLE-uh-meens) Hormones secretedby the adrenal medulla that cause rapidphysiological arousal; include adrenalineand noradrenaline.general adaptation syndromeSelye’s term for the three-stage progressionof physical changes that occur when anorganism is exposed to intense andprolonged stress. The three stages are alarm,resistance, and exhaustion.A Pioneer in Stress ResearchWith his tie off and his feetup, Canadian endocrinologistHans Selye (1907–1982) looksthe very picture of relaxation.Selye’s research at the Universityof Montreal documentedthe physical effects of exposureto prolonged stress. Hispopular book The Stress ofLife (1956) helped make stressa household word.