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- This article has content that is not included in the Wikipedia article Wikipedia:Stress (biology). Nevertheless, the WP article is a more complete treatment of the subject
Physiological stress represents a wide range of physical responses that occur as a direct effect of a stressor causing an upset in the homeostasis of the body. Upon immediate disruption of either psychological or physical equilibrium the body responds by stimulating the nervous, endocrine, and immune systems. The reaction of these systems causes a number of physical changes that have both short and long term effects on the body.
Nervous system Edit
Peripheral nervous system (PNS) Edit
The peripheral nervous system (PNS) consists of two subsystems: the somatic nervous system and the autonomic nervous system. When a physical stressor acts upon the body the sensory-somatic nervous system is triggered through stimulation of the body's sensory nerves. The signal acts as a nerve impulse and travels through the body in a process of electrical cell-to-cell communication until it reaches the automatic nervous system. Activation of the automatic nervous system immediately triggers a series of involuntary chemical responses throughout the body. Wikipedia:Preganglionic neurons release the neurotransmitter Wikipedia:acetylcholine (ACh). This stimulates Wikipedia:postganglionic neurons which release Wikipedia:noradrenaline. The noradrenaline flows directly into the bloodstream ensuring that all cells in the body's nervous and endocrine systems have been activated even in areas which the ganclionic neurons are unable to reach.
Central nervous system (CNS) Edit
The central nervous system (CNS) is made up of the brain and the spinal cord. The brain is equipped to process stress in three main areas: the amygdala, the hippocampus, and the prefrontal cortex. Each of these areas is densely packed with stress Wikipedia:corticosteroid receptors which process the intensity of physical and psychological stressors acting upon the body through a process of hormone reception. The Wikipedia:mineralocorticoid receptors (MR) make up the majority of stress corticosteroid receptors and have an extremely high affinity for Wikipedia:cortisol. This means that they are at least partially stimulated at all times and therefore are entirely activated almost immediately when a true stressor is disrupting the homeostasis of the body. The second type of receptor, Wikipedia:glucocorticoid receptors (GR), have a low affinity for cortisol and only begin to become activated as the sensation of stress reaches its peak intensity on the brain.
Stress dramatically reduces the ability of the Wikipedia:blood brain barrier (BBB) to block the transfer of chemicals including hormones from entering the brain from the bloodstream. Therefore when corticosteroids are released into the bloodstream – they are immediately able to penetrate the brain and bind to first the MR and then the GR. As the GR begin to become activated, neurons in the amygdala, hippocampus, and prefrontal cortex become over stimulated. This stimulation of the neurons triggers a Wikipedia:fight-or-flight response which allows the brain to quickly process information and therefore deal with life threatening situations. If the stress response continues and becomes chronic, the hyperactivity of the neurons begins to physically change the brain and have severe damaging effects on one's mental health. As the neurons begin to become stimulated, calcium is released through channels in their cell membranes. Although initially this allows the cells chemical signals to continue to fire, allowing nerve cells to remain stimulated, if this continues the cells will become overloaded with calcium leading to over-firing of neuron signals. The over-firing of the neurons is seen to the brain as a dangerous malfunction; therefore, triggering the cells to shut down to avoid death due to over stimulation.
Decline in both neuroplasticity (WP) and long term potentiation (WP) (LTP) occurs in humans after experiencing levels of high continual stress. To maintain homeostasis the brain is continuously forming new neural connections, reorganizing its neural pathways, and working to fix damages caused by injury and disease. This keeps the brain vital and able to perform cognitive complex thinking. When the brain receives a distress signal it immediately begins to go into overdrive. Neural pathways begin to fire and rewire at hyper-speed to help the brain understand how to handle the task at hand. Often, the brain becomes so intently focused on this one task that it is unable to comprehend, learn, or cognitively understand any other sensory information that is being thrown at it during this time. This over stimulation in specific areas and extreme lack of use in others causes several physiological changes in the brain to take place which overall reduce or even destroy the neuroplasticity of the brain. Dendritic spines found of the Wikipedia:dendrite of neurons begin to disappear and many dendrites become shorter and even less complex in structure. Wikipedia:Glia cells begin to atrophy and Wikipedia:neurogenesis often ceases completely. Without neuroplasticity, the brain loses the ability to form new connections and process new sensory information. Connections between neurons become so weak that it becomes nearly impossible for the brain to effectively encode long term memories; therefore, the LTP of the hippocampus declines dramatically.
Endocrine system Edit
When a stressor acts upon the body, the Wikipedia:endocrine system is triggered by the release of the Wikipedia:neurotransmitter, noradrenaline, by the Wikipedia:autonomic nervous system. Noradrenaline stimulates the Wikipedia:hypothalamic-pituitary-adrenal axis (HPA) which processes the information about the stressor in the Wikipedia:hypothalamus. This quickly signals the Wikipedia:pituitary gland and finally triggers the Wikipedia:adrenal cortex. The adrenal cortex responds by signaling the release of the Wikipedia:corticosteroids Wikipedia:cortisol and Wikipedia:corticotropin releasing hormone (CRH) directly into the bloodstream.
Immune system Edit
The most important aspect of the Wikipedia:immune system are Wikipedia:T-cells found in the form of Wikipedia:T-helper and Wikipedia:T-suppressor cells. Cortisol, once released into the bloodstream, immediately begins to cause division of T-Suppressor cells. This rapid cell division increases the number of T-Suppressor cells while at the same time suppressing T-helper cells. This reduces immune protection and leaves the body vulnerable to disease and infection.
There are many other reactions as well including adrenal gland “fatigue”. When adrenals become “fatigued” after being stressed, too little cortisol and other hormones are produced bringing on its own set of problems one major symptom being fatigue.
General adaptation syndrome Edit
General adaptation syndrome, first described in 1936 by Hans Selye in the journal Nature.
Selye was able to separate the physical effects of stress from other physical symptoms suffered by patients through his research. He observed that patients suffered physical effects not caused directly by their disease or by their medical condition.
Selye described the general adaptation syndrome as having three stages:
- alarm reaction, where the body detects the external stimuli
- adaptation, where the body engages defensive countermeasures against the stressor
- exhaustion, where the body begins to run out of defenses
There are two types of stress: eustress ("positive stress") and distress ("negative stress"), roughly meaning challenge and overload. Both types may be the result of negative or positive events. If a person both wins the lottery and has a beloved relative die on the same day, one event does not cancel the other — both are stressful events. Eustress is essential to life, like exercise to a muscle, however distress can cause disease. Note that what causes distress for one person may cause eustress for another, depending upon each individual's perception. When the word stress is used alone, typically it is referring to distress.
Serenity is defined as a state in which an individual is disposition-free or largely free from the negative effects of stress, and in some cultures it is considered a state that can be cultivated by various practices, such as meditation, and other forms of training.
Stress can directly and indirectly contribute to general or specific disorders of body and mind. Stress can have a major impact on the physical functioning of the human body. Such stress raises the level of Wikipedia:adrenaline and corticosterone in the body, which in turn increases the heart rate, respiration, and blood pressure and puts more physical stress on bodily organs. Long-term stress can be a contributing factor in Wikipedia:heart disease, Wikipedia:high blood pressure, Wikipedia:stroke and other illnesses.
Relationship between overwork and stressEdit
The more overworked employees feel, the more likely they are to make mistakes at work. Twenty percent of employees reporting high overwork levels say they make a lot of mistakes at work versus none (0%) of those who experience low overwork levels. They are also more likely to feel angry at their employers for expecting them to do so much. 39 percent of employees experiencing high overwork levels say they feel very angry toward their employers versus only 1% who experience low overwork levels. They also have higher levels of stress, using a standardized measure of stress that has been related in other research with physical health problems. Only 6% who experience low overwork levels are highly stressed compared with 36% of those who are highly overworked. The more symptoms of depression they experience, using a standardized measure that is used to screen people for treatment. Only 8% of those with low overwork levels have high levels of depressive symptoms compared with 21% of those who are highly overworked. The more likely they are to report that their health is poorer. Fifty-two percent of employees experiencing high overwork levels report that their health is good versus 65% of those experiencing low overwork levels. Also they more likely they are to neglect caring for themselves. Only 41% of employees who experience high overwork levels say they are very successful in taking good care of themselves versus 68% of those experiencing low overwork levels.
Coping with stressEdit
- Main article: Wikipedia:Coping (psychology)
Individuals can respond very differently to the same stressor; any given situation can cause eustress in one person and distress in another. This happens because of differences in Wikipedia:physiology and life circumstances, as well as different methods of Wikipedia:stress management. Methods of coping that work well in childhood situations often become ingrained and habitual, and often follow the child into adulthood. In the adult world, these skills can be quite inappropriate, and stress heightens as the person clings to obsolete behaviors. However, new skills can be learned, and poor coping methods replaced. There are currently many classes, books, and seminars available to help people develop better habits of managing stress.
Other approaches to dealing with stress include Wikipedia:The Alexander Technique, Wikipedia:Shiatsu, Wikipedia:T'ai Chi Ch'uan, Wikipedia:yoga and Wikipedia:meditation. For example, when Selye reviewed the physiological changes measured in practitioners of Wikipedia:transcendental meditation (TM), he concluded that such changes were the opposite of the body's reaction to stress. The therapeutic effect of TM was most distinct in people whose coping skills were poorly adapted to the stress of daily life.
Finally, a number of psychological and sociological factors have been consistently demonstrated to act as a moderator against stress in the development of chronic psychological or physical disease (such as depression or Wikipedia:hypertension). Among these many factors are chiefly: Wikipedia:optimism or Wikipedia:hope, Wikipedia:social support, Socioeconomic status (SES), Wikipedia:sense of community, and others.
Emotions and physical health Edit
The link between emotions and physical health is further supported by this paragraph from:
Dr. Ornish tells about a group of rabbits that added an unexpected tidbit to the research on heart disease. Kept in a laboratory under research conditions, the rabbits were genetically similar, and all received the same food and got the same amount of exercise; yet one group had 60 percent fewer heart attacks than the others. What was the difference? It turned out that the healthier rabbits were the ones kept in the lower cages, and the short person who fed the rabbits could reach the lower animals and pet them when feeding them. Love, it seems, is a life preserver. 
- Dantzer, R. and K. W. Kelley (1989). "Stress and Immunity: An Integrated View of Relationships Between the Brain and the Immune System." Life Sciences. 44(26): 1995-2008.
- De Kloet, E Ron; Holsboers, Florian. “Stress and the Brain From Adaptation to Disease.” Nature Reviews: Neuroscience. 23.6. (June 2005). 463-475.
- Joe, Marian; Pu, Zhenwei; Wiegert, Olof; Oitzl, Melly S; Krugers, Harm J, et al. “Learning Under Stress: How does it Work?” TRENDS in Cognitive Sciences. 4.10. (2005). 152-157.
- Khansari, D. N., A. J. Murgo, et al. (1990). "Effects of Stress on the Immune System." Immunology Today 44:26 170-175.
- Renner, Katherine H. “Effects of Naturalistic Stressors on Cognitive Flexibility and Working Memory Task Performance.” Neurocase. 16.4. (2010): 293-300.