Stress is simply a fact of nature - forces from the outside world affecting the individual. Hence, all living creatures are in a constant interchange with their surroundings (the ecosystem), both physically and behaviorally. This interplay of forces, or energy, is of course present in the relationships between all matter in the universe, whether they are living(animate) or not living (inanimate). However, there are critical differences in how different living creatures relate to their environment. These differences have far reaching consequences for survival. Because of the over abundance of stress in our modern lives, we usually think of stress as a negative experience. But from a biological point of view, stress can be neutral, negative, or positive.
Stress has driven evolutionary change (the development and natural selection of species over time). Thus, the species that adapted best to the causes of stress (stressors) have survived and evolved into the plant and animal kingdoms we now observe. Man, because of the evolution of the human brain, especially the part called the neo-cortex, is the most adaptive creature on the planet. This adaptability is largely due to the changes and stressors that we have faced and mastered. Therefore, we, unlike other animals, can live in any climate oreco system, at various altitudes, and avoid the danger of predators. Moreover, most recently, we have learned to live in the air, under the sea, and even in space, where no living creatures that we know of have ever survived. So then, what is so wrong with stress?
A brief history of stress
A key to the understanding of the negative aspects of stress is the concept of milieu interior (the internal environment of the body), which was first advanced by the great French physiologist, Claude Bernard. In this concept, he described the principles of dynamic equilibrium. In dynamic equilibrium, constancy, a steady state (situation) in the internal bodily environment, is essential to survival. Therefore, external changes in the environment or external forces that change the internal balance must be reacted to and compensated for if the organism was to survive. Examples of such external forces include temperature, oxygen concentration in the air, the expenditure of energy, and the presence of predators. In addition, diseases were also stressors that threatened the constancy of the milieu interior.