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:''For other kinds of stress see stress.'' Chronic stress is the response to emotional pressure suffered for a prolonged period over which an individual perceives he or she has no control. It involves an endocrine system response in which occurs a release of corticosteroids. While the immediate effects of stress hormones are beneficial in a particular situation, long-term exposure to stress creates a high level of these hormones that remains constant. This may lead to high blood pressure (and subsequently heart disease), damage to muscle tissue, inhibition of growth, suppression of the immune system,〔 and damage to mental health. == Physiology == Animals exposed to distressing events over which they have no control respond by releasing corticosteroids.〔Sapolsky RM. (1998). Why Zebras Don't Get Ulcers: An Updated Guide To Stress, Stress Related Diseases, and Coping. 2nd Rev Ed, W. H. Freeman ISBN 978-0-7167-3210-5〕 The sympathetic branch of the nervous system is activated, also releasing epinephrine and norepinephrine. These, if prolonged, lead to structural changes in the brain. Changes happen to neurons and their synapses in the hippocampus and medial prefrontal cortex. These produce impairments in working memory and spatial memory,〔 as well as increased aggression. Linked to impairment of the medial prefrontal cortex are deficits in the part of the striatum with which it is linked. This can bias decision-making strategies, as affected individuals shift from flexible behavior to one dominated by habit.〔 Changes also occur to dopaminergic activity in the prefrontal cortex.〔 Stress has a role in humans as a method of reacting to difficult and possibly dangerous situations. The "fight or flight" response when one perceives a threat helps the body exert energy to fight or run away to live another day. This response is noticeable when the adrenal glands release epinephrine, causing the blood vessels to constrict and heart rate to increase. In addition, cortisol is another hormone that is released under stress and its purpose is to raise the glucose level in the blood. Glucose is the main energy source for human cells and its increase during time of stress is for the purpose of having energy readily available for over active cells. The release of these hormones is evolved to be temporary. If someone is under stress for long periods of time they may have adverse health effects later on, such as hypertension and increased risk of cardiovascular disease. Chronic stress is also known to be associated with an accelerated loss of telomeres. Different factors may prolong this "fight or flight" reaction in the body. Chronic stress can be rooted in prolonged psychological stressors. For example, some studies have looked at the health effects of social discrimination in African Americans. This demographic has markedly higher hypertension levels that are attributed to higher levels of perceived social discrimination. This phenomenon has been coined John Henryism by sociologist James Sherman. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「chronic stress」の詳細全文を読む スポンサード リンク
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