What is stress?

Causes and Symptoms

Stress is a psychophysiological response, within an individual animal, to a perceived danger. Stress involves a complex interplay of nervous and hormonal reactions to internal and external stimuli. All living organisms respond to stimuli, usually by means of gene-regulating chemical messengers called hormones.

Chemistry of stress. Hormones are produced in certain cells within the individual and then target tissues elsewhere in the body; these hormones control by controlling the gene regulation within their target cells. Hormones will activate certain genes within target tissue cells while inactivating other genes. If a hormone activates the control region of a gene so that the gene is “on,” then it can be “read” by an enzyme (RNA polymerase), thereby leading to RNA and protein production. The produced protein may affect cellular chemical processes or may affect the expression (the on/off status) of other genes. In the latter case, the protein would be a type of intracellular hormone called an alarmone.

If a hormone inactivates the control region of a gene so that the gene is “off,” then RNA polymerase will be unable to read the DNA nucleotide sequence of the gene. Therefore, no RNA and no protein will be produced. In this fashion, a hormone may activate certain genes while inactivating others. Consequently, a hormone controls what happens within the cell.

Such control is critical within complex multicellular organisms such as animals. Different cells specialize to become different tissues and organs (such as eyes, ears, hair, intestines, the heart, and so on) under the specific influence of hormones. Additionally, changes in the development of an organism over time involve changes in gene expression caused by hormones. Critical developmental changes in an individual must occur at precise times when a hormone is produced and acts correctly upon the proper array of genes in target cell tissues. When a hormone does not act correctly or issues incorrect instructions to genes, the homeostatic stability of the organism becomes disrupted. Incorrect proteins are produced in the wrong cells at the wrong times, thereby disturbing development and possibly threatening the organism’s survival.

In higher animals, including humans, the body is regulated by hormones and by complex nervous systems that evolved from hormones. Most hormones are produced and secreted from the glands of the endocrine system, including the pituitary, thyroid, and adrenal glands as well as numerous organs, tissues, and cells throughout the body. The nervous system is an array of several trillion nerves concentrated in the brain and spinal cord and extending peripherally to virtually every cellular region of the body. The two systems are tightly interconnected. Both the endocrine and nervous systems at some point involve the secretion of hormones. Nerve tissue secretes hormones called neurotransmitters between electrically conducting cells called neurons.

Physiological responses to stress
. Stress is therefore a biochemical response to danger that occurs within animals. The nervous system detects danger from internal or external stimuli, usually external stimuli such as predators, competitors, or life-threatening events. Increased electrical conductivity along millions of nerve cells targets various tissues to prepare the body for maximum physical activity. Among the tissues affected will be the skeletal muscles, the heart muscle, the hormone-secreting glands of the endocrine system, the immune system, the stomach, and blood vessels. Under nerve-activated stress, skeletal muscles will be poised for contraction. The heart will beat faster, thereby distributing more blood and nutrients to body cells, in the process accelerating the breathing rate to distribute more oxygen. Blood vessels will constrict. The stomach and other intestinal organs will decrease their activity, including a decreased production of mucus that protects against acid.

Heightened nerve activity also will trigger the production of various hormones from the immune system, specifically hormones that influence bodily metabolism such as thyroxine and epinephrine (adrenaline). These hormones target body tissue cells to prepare the body for increased output in the face of danger. Massive production of epinephrine will trigger maximum physical readiness and extraordinary muscular output, a phenomenon often referred to as the fight-or-flight response.

These physiological changes within an animal facing danger are important survival adaptations that evolved very early in the history of animal life on earth. Stress is a fact of life for animals because they must eat to survive. Competition for available food resources and avoidance of predators must be faced by all animals, including humans. While predation by larger animals is of little worry to current-day modern humans, the struggle for available resources remains. Furthermore, human technology has created stresses of an entirely different character.

The fight-or-flight stress response and other evolutionary stress adaptations endure within the individual for only seconds or minutes. Such natural stresses are to an individual’s advantage, ensuring survival. The stresses that humans face are based on these behavioral adaptations. Much human stress is artificial, however, and lasts not for minutes but for hours, days, weeks, months, and years. Such stresses involve the same nervous and endocrine system responses, but they are usually brought about by perceived danger, not true danger.

Human societies impose norms and rules for the behavior of the individuals who compose the society. People must adhere to the societal norms or face punishment. In fast-paced technological societies, increasing bureaucratization and organization place less emphasis on the individual and more emphasis on process and productivity. People must face deadlines, be on time, produce quotas, generate company profit, and meet the demands of family, colleagues, and administration simultaneously. The result is a continuous
fight-or-flight response in which individuals fear losing their jobs and thus the means of supporting themselves and their families.

The physiological manifestations of prolonged stress are devastating. Continued hyperactivity of nerve impulses and overproduction of hormones at incorrect developmental stages lead to the abnormal functioning of internal organs. The stomach undersecretes mucus, thereby leading to ulcers. The heart muscle contracts too rapidly, leading to higher pulse and respiration rates. The blood vessels constrict for lengthy periods of time, thereby causing the heart to pump harder and leading to high blood pressure and heart disease. Hormone overproduction leads to incorrect cell instructions and gene activation/inactivation, causing abnormal tissue functioning and cellular transformation leading to cancer. The immune system weakens under abnormal signaling by hormones, thereby decreasing the body’s ability to defend itself from disease.

Newer research on stress response in women has uncovered a mechanism of stress response that is of interest given this upswelling of constant stress. Work by Shelley E. Taylor has documented an alternative to “fight or flight” known as “tend and befriend.” Potentially linked to oxytocin, such tend-and-befriend behavior may help to facilitate relaxation and interpersonal bonding in response to stress. The potential stress response promises longer-lasting benefits, adaptively connecting humans to their social groups.

Stress and disease. A wide variety of human illnesses and disorders have been associated with stress. Heart disease, cancer, stroke, mental illness, allergies, accidents, asthma, chronic fatigue, depression, suicide, and deviant behavior are among the many illnesses and disorders that are considered by scientists to be stress-related illnesses. These stress-related diseases and disorders are responsible for the majority of deaths, hospitalizations, and visits to physicians by people in highly technological societies such as the United States, Japan, and Western Europe. In the United States alone, several billion dollars are spent each year for medications to treat stress-related illnesses that otherwise could be prevented by antistress methodologies.

Before the advent of industrialization in Europe and North America, the leading killers of humans were bacterial and viral diseases, which continue to be the principal killers of humans in the pretechnological and emerging technological countries of the Middle East, Asia, Africa, Latin America, and Oceania. European and North American industrialization has been accompanied by prodigious advances in medical science and the eradication or control of many microorganismal diseases. The psychological demands of fast-paced living and the dehumanized expectations of technological societies, however, have produced a plethora of stress-generated diseases and disorders, some of which had been masked by microorganismal diseases.

There still is some debate concerning the causal relationship between stress and illness, despite overwhelming scientific evidence demonstrating bodily responses to stressful situations. Abnormal nerve hyperactivity and prolonged, abnormal secretions of gene regulatory hormones from various endocrine glands disrupt the balanced
homeostasis of many different body systems. Immune system reduction often occurs during stress, thereby making a stressed individual more susceptible to contracting infectious bacterial and viral diseases.

A clear linkage exists between the occurrence of stress in people and their subsequent susceptibility to infectious disease. Furthermore, there is a tendency for strokes, heart attacks, cancer, and sudden death to occur in individuals who recently have experienced major traumatic events in their lives. Too little attention has been given to the effects of everyday living upon the physical well-being of people. Environmental stimuli, nervous and endocrine systems, and physiological rhythms within the body are intricately connected.

Most bodily processes follow a self-regulatory, homeostatic pattern that is rhythmic, linear, stable, and predictable. For example, the beta cells of the islets of Langerhans in the pancreas secrete the hormone insulin in response to elevated blood glucose levels, whereas the alpha cells in these same islets secrete the hormone glucagon in response to low blood glucose levels. Likewise, the body chemically maintains a constant blood temperature (37 degrees Celsius), pH (7.35 to 7.45), calcium levels, and so on. The heart muscle requires an electrical stimulus approximately once per second to trigger a wave of muscular contractions throughout the myocardium via the sinoatrial and atrioventricular nodes.

Linear, balanced physiological rhythms are sensitive to subtle chemical changes in the cellular and organismal environment. An orderly, homeostatic process in the body can collapse into disorderly, nonlinear, and unpredictable chaos because of the slightest disturbance. Stress is a disturbance that imbalances the nervous and endocrine systems, which subsequently imbalance cells and organ systems throughout the human body. Physiological systems become unstable, and disease or cancer may ensue.

Treatment and Therapy

Psychologists, psychiatrists, physicians, and other medical professionals are becoming more aware of the physiological effects of stress. Through this awareness, professionals have sought to examine whether there are any characteristic styles of stress response. In response, psychologists have identified two principal behavioral types when it comes to stress among humans: type A behavior pattern and type B behavior pattern. Type A individuals are highly anxious, task-oriented, time-conscious, constantly in a rush to accomplish their jobs and other objectives, and somewhat prone to hostility. Research indicates that type A individuals may have a higher incidence of heart disease. Increasingly, the hostility component of type A behavior is seen as a very important contributing factor. On the other hand, type B individuals are more relaxed and experience less stress. Nevertheless, it should be emphasized that behavior is a continuum: Different people may exhibit varying degrees of type A and B behavior patterns. Given this discovery, it is not uncommon for professionals to recommend to their stressed clients to monitor their participation in type A behavior and to try behaving
more in kind with type B behavior patterns.

Another important focus for health care has become the prevention, management, and treatment of stress itself. Health education programs emphasize the importance of physical fitness and stress reduction in everyday living. Stress-reducing methodologies for the individual include time management, peer counseling and support, spending longer amounts of time relaxing, strengthening family bonds, improving self-esteem, exercise, and learning to reframe how daily life events are interpreted, such as may be done through cognitive behavior therapy. These approaches greatly enhance an individual’s quality of life and help the individual to cope positively with stressful events. All these stress reduction techniques emphasize an individual’s personality and the more efficient use of an individual’s free time. Relaxation, social interaction, and physical activity help the body to return to normal physiological rhythms following the numerous stressful events that every person faces daily. Individuals in American and Western societies are coming to realize that a slower, more relaxed living pace is essential for reducing stress and the millions of cases of stress-related disease that occur each year.

Perspective and Prospects

Because stress is a major contributor to illness and disease, a major objective of health care professionals is the identification of stress initiators and the reduction of stress in the general population. Stress cannot be eliminated entirely in any individual. Humans always will experience stress as a result of their continuous interactions with one another and with the environment. Stress is an important survival adaptation for animal life on earth. Nevertheless, stressful events in an individual’s life serve as negative environmental stimuli that hyperactivate the human nervous and endocrine systems to create a fight-or-flight response. When this fight-or-flight response is maintained for abnormally long periods of times, prolonged elevations in nervous and hormonal activity modify body tissues and the developmental gene expression within cells to produce abnormal growths (such as cancers) and abnormal system functioning (such as diabetes mellitus). Breakdown of the human immune system under stress makes the body less capable of fighting spontaneous tumors, cancers, and infectious disease. The net result from physiological stress is illness, disease, rapid aging, and death.

Stress reduction should be a prime focus of medical research and education. The simplicity of educating the public with respect to stress can yield incredible savings in terms of lives saved, quality of lives improved, length of human life spans increased, and money saved. Some researchers propose that stress reduction not only can yield enormous health benefits but also can produce greater industrial productivity, happier people, and considerably less crime. It is expected that additional research into oxytocin, the tend-and-befriend response, and yet undiscovered mechanisms of stress response will contribute meaningfully to decreased stress and increased mental and physical well-being.

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