The term stress had none of its contemporary connotations before the 1920s. It is a form of the Middle English destresse, derived via Old French from the Latin stringere, "to draw tight." It had long been in use in physics to refer to the internal distribution of a force exerted on a material body, resulting in strain. In the 1920s and 1930s, the term was occasionally being used in biological and psychological circles to refer to a mental strain, unwelcome happening, or, more medically, a harmful environmental agent that could cause illness. Walter Cannon used it in 1926 to refer to external factors that disrupted what he called homeostasis.
Homeostasis is a concept central to the idea of stress. In biology, most biochemical processes strive to maintain equilibrium, a steady state that exists more as an ideal and less as an achievable condition. Environmental factors, internal or external stimuli, continually disrupt homeostasis; an organism’s present condition is a state in constant flux wavering about a homeostatic point that is that organism’s optimal condition for living. Factors causing an organism’s condition to waver away from homeostasis can be interpreted as stress. A life-threatening situation such as a physical insult or prolonged starvation can greatly disrupt homeostasis. On the other hand, an organism’s effortful attempt at restoring conditions back to or near homeostasis, oftentimes consuming energy and natural resources, can also be interpreted as stress. In such instances, an organism’s fight-or-flight response recruits the body’s energy stores and focuses attention to overcome the challenge at hand. The ambiguity in defining this phenomenon was first recognized by Hans Selye in 1926 who loosely described stress as something that "…in addition to being itself, was also the cause of itself, and the result of itself." First to use the term in a biological context, Selye continued to define stress as "the non-specific response of the body to any demand placed upon it." Present-day neuroscientists including Bruce McEwen and Jaap Koolhaas believe that stress, based on years of empirical research, "should be restricted to conditions where an environmental demand exceeds the natural regulatory capacity of an organism." Despite the numerous definitions given to stress, homeostasis appears to lie at its core.
Biology has progressed in this field greatly, elucidating complex biochemical mechanisms that appear to underlie diverse aspects of stress, shining a necessary light on its clinical relevance and significance. Despite this, science still runs into the problem of not being able to settle or agree on conceptual and operational definitions of stress. Because stress is ultimately perceived as a subjective experience, it follows that its definition perhaps ought to remain fluid. For a concept so ambiguous and difficult to define, stress nevertheless plays an obvious and predominant role in the everyday lives of humans and nature alike.
Effect of stress on the immune system
Stress is the body’s reaction to any stimuli that disturb its equilibrium. When the equilibrium of various hormones is altered the effect of these changes can be detrimental to the immune system. Much research has shown a negative effect stress has on the immune system, mostly through...