1 Much of what we know about the body's response to stress is the result of pioneering research by Hans Selye (1907- 1982), the famed stress researcher known affectionately as "Dr. Stress." Selye found that the body responds in a similar manner to various stressors—cold, noise, infectious agents, pressures on the job, or mental stress in the form of worry or anxiety. He recognized that specific stressors, such as an invading virus, do elicit specific reactions in the body. But layered over these specific responses is a more general response to stress, which he called the general adaptation syndrome (GAS) (also called the stress response). The general adaptation syndrome consists of three stages, each of which we consider below.
2 The alarm stage is the body's first stage of response to a stressor, during which its defenses prepare for action. Suppose a car ahead of you on the road suddenly veers out of control. This is an immediate stressful event. Your heart starts pounding faster, speeding the flow of blood to your extremities and providing muscles with the oxygen and fuel they need to take swift action, such as performing an emergency maneuver to avoid a collision. The body's response during the alarm stage is called the fight-or-flight response because it is characterized by biological changes that prepare the body to deal with a threat by either fighting it off or fleeing from it.
3 The alarm stage is accompanied by strong physiological and psychological arousal. Our hearts pound, our breathing quickens, sweat pours down our foreheads, and we are flooded with strong emotions such as terror, fright, anxiety, rage, or anger.
4 Different stressful events may trigger the alarm stage of the GAS. The threat may be physical, as in an attack by an assailant, or psychological, as in an event that induces fear of failure (a professor handing out an examination, for example). In some people, the alarm is triggered whenever they meet a new person at a social gathering; they find themselves sweating heavily and feeling anxious, and they may become tongue-tied. In others, the body alarm system is activated whenever they visit the dentist. Whether the perceived threat is physical or psychological, the body's response is the same.
5 The alarm stage is like a "call to arms" that is prewired into the nervous system. This wiring is a legacy inherited from our earliest ancestors who faced many potential threats in their daily lives. A glimpse of a suspicious-looking object or a rustling sound in the bush might have cued them to the presence of a predator, triggering the fight-or-flight response, which helped prepare them to defend themselves against a threat. But the fight-or-flight response didn't last long. If they survived the immediate threat, their bodies returned to their normal state. If they failed, they simply perished.
6 Death may occur within the first few hours or days of exposure to a stressor that is so damaging (such as extreme cold) that its persistence is incompatible with life. But if survival is possible and the stressor continues, the body attempts to adapt to it as best it can. Selye called this part of the GAS the resistance stage (also called adaptation stage). During this stage, the body attempts to return to a normal biological state by restoring spent energy and repairing damage. Yet arousal remains high, though not as high as during the alarm reaction. This prolonged bodily arousal may be accompanied by such emotional reactions as anger, fatigue, and irritability.
7 If the stressor persists, the body may enter the final stage of the GAS—the exhaustion stage. Heart rate and respiration now decrease to conserve bodily resources. Yet with continued exposure to stress, the body's resources may become seriously depleted and the individual may develop what Selye called "diseases of adaptation"—stress-related disorders such as kidney disease, heart disease, allergic conditions, digestive disorders, and depression. Some people are hardier than others, but relentless, intense stress can eventually exhaust anyone. Figure 15.2 shows the changes that occur in the body's level of resistance across the three stages of the GAS.
8 A sensitive alarm system may have helped our ancient ancestors survive many of the physical threats they faced. Yet the alarm reaction was designed not to last very long. Our ancestors either escaped a predator or fought it off; within seconds, minutes perhaps, the threat was over and their bodies returned to their normal, pre-aroused state. The stresses of contemporary life are more persistent. Our ancestors didn't need to juggle school and jobs, fight daily traffic jams, or face the daily grind of working a double shift to make ends meet. The reality for many of us today is that the stressful demands of everyday life may repeatedly activate our alarm reaction day after day, year after year. Over time, persistent stress may tax our bodies' resources to the point where we become more susceptible to stress-related disorders.
From Psychology Concepts and Applications, by Jeffrey S. Nevid, Houghton Mifflin Company, pp. 598-600
 re·sponse A reaction, that an organism may have in response to a specific cause, mechanism, or stimulus.
 a·dap·ta·tion Something that is changed or changes so as to become suitable to a new or special situation.
 a·larm A sudden fear caused by the realization of danger.
 fight-or-flight A set of physiological (body) changes, such as increases in heart rate, arterial blood pressure, and blood glucose, initiated… to mobilize body systems in response to stress.
 phy·si·o·lo·gi·cal Being in a part of or typical of the normal functioning of a living organism
 trig·ger Cause.
 le·ga·cy Something handed down from an ancestor. In this case it is a genetic trait.
 in·her·i·ted Biology. To receive (a characteristic) from one's parents by genetic transmission.
 per·ishedTo die or be destroyed.
 ex·po·sure The condition of being exposed to forces of nature so as to cause harm.
 in·com·pat·i·ble Not able to exist together at the same time. Extreme stress can cause death.
 re·sis·tance A force that tends to oppose..
 a·rou·sal A state of being stired up or excited.
 ex·haus·tion The state of being exhausted; extreme fatigue. Lacking any energy or ability to resist.
 jug·gle To have difficulty holding; to balance insecurely, to keep going under a demanding situation.
 ac·ti·vate To set in motion; make active or more active.
 dis·or·der An ailment (or sickness) that affects the function of mind or body.