How the stress affect our lifie?

When a person appraises an event as stressful, the body undergoes a number of changes that heighten physiological and emotional arousal. First, the sympathetic division of the autonomic nervous system is activated. The sympathetic division prepares the body for action by directing the [[KW]] adrenal glands [[/KW]] to secrete the [[KW]] hormones [[/KW]] epinephrine (adrenaline) and norepinephrine (noradrenaline). In response, the heart begins to beat more rapidly, muscle tension increases, blood pressure rises, and blood flow is diverted from the internal organs and skin to the [[KW]] brain [[/KW]] and muscles. [[KW]] Breathing [[/KW]] speeds up, the pupils dilate, and perspiration increases. This reaction is sometimes called the fight-or-flight response because it energizes the body to either confront or flee from a threat.
Another part of the stress response involves the hypothalamus and the pituitary gland, parts of the brain that are important in regulating hormones and many other bodily functions. In times of stress, the hypothalamus directs the pituitary gland to secrete adrenocorticotropic hormone. This hormone, in turn, stimulates the outer layer, or cortex, of the adrenal glands to release glucocorticoids, primarily the stress hormone cortisol (see Hydrocortisone). Cortisol helps the body access fats and carbohydrates to fuel the fight-or-flight response.
Canadian scientist Hans Selye was one of the first people to study the stress response. As a medical student, Selye noticed that patients with quite different illnesses shared many of the same symptoms, such as muscle weakness, weight loss, and apathy. Selye believed these symptoms might be part of a general response by the body to stress. In the 1930s Selye studied the reactions of laboratory rats to a variety of physical stressors, such as heat, cold, poisons, strenuous exercise, and electric shock. He found that the different stressors all produced a similar response: enlargement of the adrenal glands, shrinkage of the thymus gland (a gland involved in the immune response), and bleeding stomach ulcers.
Selye proposed a three-stage model of the stress response, which he termed the general adaptation syndrome. The three stages in Selye’s model are alarm, resistance, and exhaustion. The alarm stage is a generalized state of arousal during the body’s initial response to the stressor. In the resistance stage, the body adapts to the stressor and continues to resist it with a high level of physiological arousal. When the stress persists for a long time, and the body is chronically overactive, resistance fails and the body moves to the exhaustion stage. In this stage, the body is vulnerable to disease and even death.