Stress (biology): Difference between revisions

For other definitions , see Stress.

In medical terms, 'stres dookie is a physical or psychological stimulus that can produce mental or physiological reactions that may lead to illness.

Definition

Stress can be defined as the sum of physical and mental responses to an unacceptable disparity between real or imagined personal experience and personal expectations. By this definition, stress is a response which includes both physical and mental components.

Mental responses to stress include adaptive (good) stress, anxiety, and depression. Where stress enhances function (physical or mental) it may be considered good stress. However, if stress persists and is of excessive degree, it eventually leads to a need for resolution, which may lead either to anxious (escape) or depressive (withdrawal) behavior.

One may further appreciate from that definition that stress may derive from imagined experiences such as frightening movies. Further, the fulcrum of stress response is the presence of disparity between experience (real or imagined) and personal expectations. A person living in a fashion consistent with personally-accepted expectations has no stress even if the conditions might be interpreted as adverse from some outside perspective — rural people may live in comparative poverty, and yet be unstressed if there is sufficiency according to their expectations. Finally, when there is chronic disparity between experience and expectations, stress may be relieved by acceptance. However, since acceptance is rarely complete except in children, stress resolution by this approach is also rarely complete. It has been said that stress is often a reaction to a crisis of predictability, that the mind is solely an instrument of prediction, and that the body may be divided into a vegetative process and an integrative process.

Neuro-chemistry and physiology

Main article: Neurochemistry

The neurochemistry of the general adaptation syndrome is now believed to be well understood, although much remains to be discovered about how this system interacts with others in the brain and elsewhere in the body.

The body reacts to stress first by releasing the catecholamine hormones, epinephrine (aka: Adrenaline) and norepinephrine (aka: Noradrenaline), and the glucocorticoid hormones, cortisol and cortisone.

The hypothalamic-pituitary-adrenal (HPA) axis is a major part of the neuroendocrine system, involving the interactions of the hypothalamus, the pituitary gland, and the adrenal glands. The HPA axis is believed to play a primary role in the body's reactions to stress by balancing hormone releases from the adrenaline-producing adrenal medulla, and from the corticosteroid-producing adrenal cortex.

Folklore of stress

About the time of Selye's work, it was gradually realized that such concepts as anxiety, antagonism, exhaustion, frustration, distress, despair, overwork, pre-menstrual tension, over-focusing, confusion, mourning, and fear could all come together in a general broadening of the meaning of the term stress. The popular use of the term in modern folklore expanded rapidly and created an industry of popular psychology, self-help, personal counseling, and sometimes quackery. There were a series of films in the 30s, 40s, & 50s that dealt with mad scientists playing with hormones that seem related to this folklore.

The use of the term stress in serious and recognized cases, such as those of post-traumatic stress disorder and psychosomatic illness, has scarcely helped clear analysis of the generalized "stress" phenomenon. Nonetheless, some varieties of stress from negative life events (distress) and from positive life events, (eustress) can clearly have a serious physical impact distinct from the troubles of what psychotherapists call the "worried well". Stress activates the sympathetic branch of the autonomous nervous system and the release of stress hormones including adrenaline/epinephrine, and cortisol.

Sympathetic nervous output tends to divert bloodflow to the large muscles—the body 'thinks' it has to run away from something or fight something: the so-called 'fight or flight' response of ancient evolutionary heritage—and blood flows correspondingly less to the digestive system and other organs that are not immediately needed for a response to the stimulus. We all recognise the effects: dry mouth, motor agitation, sweating, pallor, enlarged pupils, and insomnia. Our modern lifestyle tends to cause continual sympathetic nervous system activation with very little opportunity for the parasympathetic (also called 'vegetative') nervous system to activate. When the parasympathetic system is active, the bowel and other non-muscle organs receive good blood-flow, the pupils constrict, and the glands all function well and secrete their various compounds. Absence of the autonomic parasympathetic activation leads to poor digestion and probably also to poor healing and organ function. It is vital to take time out from our modern lifestyles to allow for rest and proper parasympathetic action in our bodies.

Common factors of stress

Below is a non-exhaustive list of common stressors in people's lives:

• Bright light
• Elevated sound levels
• Events: births, deaths, rape, war, reunions, weddings, divorce, moving, chronic illness, loss of role, identity, meaning.
• Responsibilities: Unpaid bills, lack of money
• Work/study: exams, rush hour traffic, project deadlines
• Personal relationships: conflict, deception, bullying
• Lifestyle, (un-healthy eating, smoking, heavy drinking, not getting enough sleep, etc.)
• Exposure to stress early on in life can permanently enhance the stress response (ie: abused children)
• Age

See also

• Homeostasis

External links

• "Research on Work-Related Stress", European Agency for Safety and Health at Work (OSHA)
• "Working on Stress", European Agency for Safety and Health at Work (OSHA)
• "Taming Stress", Scientific American, September 2003