THE BIOLOGICAL MECHANISMS OF STRESS

Stress is clearly part of the human condition. Because of its universal occurrence, stress is not looked at in terms of its presence or absence but, rather, according to its intensity and the effect it has on individuals. Many of us seem to cope well with the pressures of work and family life that we encounter daily. But when and why is stress harmful to us? Consider what happens to the human body when it 1S subjected to a strain or pressure of some kind.

As Melhuish (1978), a physician specializing in stress-related illnesses, has suggested, stress is the product of many thousands of years of evolution, and human survival in a hostile environment required a quick physical response to dangers. In other words, the body "developed the ability to rev-up" for a short time. This mobilization of forces is the well-known fight-or-flight reaction mentioned earlier. "Primitive man expended this burst of energy and strength in physical activity, such as a life and death struggle with a predator."

Modern humans have retained their hormonal and chemical defense mechanisms through the millennia. But for the most part, today's lifestyles do not permit physical reaction to the stress agents we face. Attacking the boss, hitting the biology teacher who has refused to accept overdue homework, or smashing an empty automatic teller machine are not solutions allowed by today's society. Today, even the nonaggressive "flight" reaction would hardly be judged appropriate in most situations. The student who walks out in the middle of a difficult exam, the teacher who flees from a rowdy class, or the assembly worker who dashes out in the middle of a shift will likely suffer adverse consequences for their actions. Our long-evolved defense mechanisms prepare us for dramatic and rapid action but find little outlet otherwise. The body's strong chemical and hormonal responses, then, are like frustrated politicians: all dressed up with nowhere to go.

This waste of our natural response to stress may harm us. Although scientists do not fully understand this process, many believe that our thought patterns regarding ourselves and the situations we are in trigger events within the two branches of our autonomic nervous system, the sympathetic and the parasympathetic. To paraphrase Albrecht (1979), in a situation of challenge, tension, or pressure, the sympathetic nervous system comes into play and activates a virtual orchestra of hormone secretions. Through this activation, the hypothalamus, recognizing a danger, triggers the pituitary gland. The pituitary releases hormones, causing the adrenal glands to intensify their secretion of adrenaline into the bloodstream. Adrenaline, along with corticosteroid hormones released through the same process, enhances one's arousal level. All these stress chemicals stimulate the brain, nerves, heart, and muscles to action. These physiological changes combine to improve individual performance: Blood supply to the brain is increased, initially improving judgment and decision-making ability; the heart speeds up, increasing blood supply to the muscles; lung function improves; and glucose and fats are released into the bloodstream to provide additional energy. As part of these physiochemical changes, blood pressure rises (due to increased cardiac output), and blood is redeployed to voluntary muscles from the stomach and intestines as well as from the skin, resulting in the cold hands and feet often associated with a nervous disposition (Albrecht, 1979).

Although these changes result from actions of the sympathetic nerves, parasympathetic nerves can induce an opposing state of relaxation and tranquility. As Albrecht notes, "People who have spent much of their time in an over-anxious or tense state have difficulty in bringing into action the parasympathetic branch" and its helpful capabilities. All of the body's "rev-up" activity is designed to improve performance. But if the stress that launches this activity continues unabated, researchers believe the human body will weaken from the bombardment of overstimulation and stress-related chemicals. Many long-term effects of pressure are described by Melhuish (1978) in Table 1.1.

TABLE 1.1  - Effects of Stress on Bodily Functions - SOURCE: A. Melhuish: Executive Health (London: Business Books), 1978.