From: "Stress." Britannica Student Encyclopedia 2003 Encyclopdia Britannica Online. 24 Feb, 2003 :

The body's response to a threat or demand arising from a new or changing situation is called stress. The emotional and physical experiences of stress can be caused by a complex and tense situation. Under stress, the body makes rapid physiological changes, called adaptive responses, to deal with threatening situations. In the first stage of stress, alarm, the body mobilizes its fight or flight defenses, either to resist the stress-causing factor or adapt to it. In this stage, the pituitary-adrenocortical system pours hormones into the bloodstream. The pulse quickens, the lungs take in more oxygen to fuel the muscles, blood sugar increases to supply added energy, digestion slows, and perspiration increases.

In the second stage of stress, resistance, the body begins to repair the incidental damage caused by the arousal in the alarm stage. If the stressful situation is resolved, the stress symptoms vanish. If the stressful situation continues, however, a third stage, exhaustion, sets in, and the body's adaptive energy runs out. This stage may continue until vital organs are affected, and then disease or even death can result.

Medical scientists divide people's behavior into two types, depending on the individuals' reactions to stress. People with type-A behavior react to stress with aggressiveness, competitiveness, and self-imposed pressure to get things done. Type-A behavior has been linked to increased rates of heart attack and other diseases. In the United States two of every three men and one of every two women demonstrate type-A characteristics. People with type-B behavior may be equally serious in their intentions, but are more patient, easygoing, and relaxed. Life events may have a strong effect on an individual's susceptibility to disease. The Holmes-Rahe Social Readjustment Rating Scale ranks a number of life events in order of their estimated level of stress. Death of a spouse has a rating of 100 stress points, making it the most stressful event on the list, while minor violations of the law have a rating of only 11 points. Stress is a major factor in diseases that have a significant psychosomatic component, that is, diseases whose physical symptoms are induced or aggravated by mental or emotional disturbances. Stress-related disorders compose 50 to 80 percent of all illnesses, though stress may not be the only cause. Such disorders include high blood pressure, cardiovascular disease, arthritis and other inflammatory diseases, asthma, insomnia and other sleep disturbances, and anorexia nervosa and other eating disorders. Stress is also related to migraine headaches, ulcers, respiratory or lung diseases, and skin disturbances. Although a link between stress and cancer is uncertain, some experts believe there is a type-C personalityone who is cancer prone because of chronic stress.

Stress experts frequently emphasize that stress can be good as well as bad and advise their patients to make it work for them as a source of energy. They suggest the following ways to manage stress:

(1) Have a code of life and live positively.
(2) Set priorities to avoid unnecessary time pressures.
(3) Allow time for pleasurable activities such as taking walks or talking with friends.
(4) Exercise regularly as an outlet for stress.
(5) Eat a sensible diet to maintain the energy needed to cope with stress.
(6) Learn self-relaxation techniques such as deep breathing, muscle relaxation, and meditation.

Definition of stress in biological terms:

Stress can be any condition which causes the release of certain hormones, called glucocorticoids, into the blood stream. These hormones are released by a mass of tissue, called the adrenal gland, which lies on top of the kidneys.

Hormones are chemicals which are released by certain cells of the body, travel through the blood, and tell other cells in the body what to do; they are a kind of messenger.

Glucocorticoids are messengers which tell the body that it is in a stressful situation. They tell the heart to beat faster, they tell the muscles to get ready to respond if needed, and they tell the stomach to stop digesting food. Basically, they get the body ready to fight or run away from a stress.

You know that many functions of the body, for example heartbeat and digestion, are not under voluntary control, which also means that they continue during sleep. These functions are controlled by the autonomic nervous system, which has two subsystems, the sympathetic and the parasympathetic nervous systems.

The sympathetic nervous system reacts when the organism is threatened. This system is therefore responsible for all the physiological reactions of your body to a stress factor. For example, it increases heartbeat and breathing rate, digestion stops and the pupils dilate.

The parasympathetic nerve fibers connect to the same organs as the sympathetic nerve fibers, but they cause just the opposite effects. After the stress is over, the parasympathetic system tells the body to go back to normal , the stress is over. The heart decreases, the stomach relaxes, digestion starts again, breathing slows down, and the pupils of the eyes contract. Thus, the parasympathetic division rests the body after stress and accumulates energy for the next emergency. The sympathetic reaction to stress has evolved to help animals in situations of danger, in which they are face with the choice of "fight or flight". Humans have evolved beyond the necessity to defend our lives on a daily basis, but exams, dentist appointments, first dates and other stressors of the modern world all call upon our sympathetic nervous system! We humans experience less acute stress and more chronic stress (the type cause by a demanding job or a difficult relationship) than ever. This chronic stress keeps our body in a constant out of equilibrium state and imposes great strains on our various systems. Chronic stress is known to cause problems of the heart, liver; lungs and kidneys and to be linked to a variety of diseases, most notably cancer. Chronic stress also causes depression and leads to self-destructing behaviors such as smoking, alcoholism, drug abuse and suicide,

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