+ biopsychology of stress- part2

This text is a summary of 17th part of the book "biopsychology" writen by John P. J. Pinel and translated into persian (Farsi) By A.R Fazeli, student of psychology courses in Imam Qomeini institute for education and research as a work of phsiologic psychology class by M.K Khoda Panahi PhD


     1.     The Stress Response
     2.     Stress and Ulcers
     3.     Psychoneuroimmunology: Stress and Infection
     4.     Stress and the Hippocampus
Lecture Notes

1.     The Stress Response

-     Selye first described the stress response in the 1950's; he identified several physiological responses to stress, emphasizing the role of the anterior pituitary-adrenal cortex system and the effects of stress on the release of ACTH, and glucocorticoids.  He also recognized the dual nature of stress: acute stress elicited adaptive changes that allowed an organism to cope with the stressor, but chronic stress produced changes that were maladaptive

-     recent research has also implicated the importance of the sympathetic nervous system's release of epinephrine and norepinephrine in the response to stress

-     McEwen (1994) hypothesized that the magnitude of the stress response was dependent upon 3 factors: the stressor, the individual, and strategies to cope with stress

-     Selye's work remains important to the psychological sciences because it provided a link through which psychological factors might impact upon physical illness.  Psychosomatic illnesses are ones that have a physical basis that is greatly influenced by psychological factors.  Two examples of psychosomatic illness include ulcers and infection.

2.     Stress and Ulcers

-     gastric ulcers are painful lesions to the lining of the stomach and small intestine; stress has been implicated in their development, with the key factor being a stress-induced increase in acidic gastric secretions accompanied by decreased blood flow through the wall of the stomach.

-     recent evidence has suggested that the bacteria Helicobacter pylori are responsible for all ulcers except by those caused by nonsteroidal anti-inflammatory drugs.  However, it seems as though H. pylori by itself is not sufficient to induce the formation of ulcers, as it is found in about 75% of all control subjects, too.  Currently, researchers believe that stress-induced increases in gastric secretions and decreases in blood flow interact with H. pylori to produce ulcers.

3.     Psychoneuroimmunology: Stress and Infection

-     psychoneuroimmunology is the study of interactions among psychological, nervous system, and immune system responses allows a theoretical basis for studying a person's resistance to disease and infection

-     the immune system puts up barriers to keep the body from being taken over by invading microorganisms

-     phagocytosis is a nonspecific mechanism by which foreign microorganisms are destroyed; this process is carried out by macrophages
-     there is also a second, more specific mechanism for dealing with foreign microorganisms and debris

-     antigens are protein molecules on a cell's surface that identify it as foreign or native

-     lymphocytes are specialized white blood cells, produced in the bone marrow, and stored in the lymphatic system; there are two types of lymphocytes, that each mediate a form of immunological defense:

     1) T cells are lymphocytes that destroy invading microorganisms in a process called cell-mediated immunity; and

     2) B cells are lymphocytes that manufacture antibodies (lethal receptor molecules) against antigens encountered on foreign cells and debris, in a process called antibody-mediated immunity
-     in humans, stress from sources such as final examinations, sleep deprivation, divorce, bereavement etc., has been shown to decrease the effectiveness of the immune system.  Unfortunately, these results are not straightforward to interpret as there are many possible confounds; for example, stressed subjects may report more illnesses because they expect to be ill, the experience of illness may be worse under stress, or stress may cause illness-inducing behavioral changes rather than the illness itself (e.g., decreases in sleep; alterations in diet)

-     in support of these human findings, similar results have been seen in laboratory animals exposed to electric shocks, social defeat, overcrowding etc.  Together, these converging lines of data suggest that stress may play a major role in our susceptibility to many infectious diseases.

-     stress may affect the immune system by affecting hormonal activity mediated through the anterior pituitary-adrenal cortex system and the sympathetic adrenal medulla system; for example, both T-cells and B-cells have receptors for glucocorticoids and for norepinephrine and epinephrine, which are all released in very high levels during periods of stress

4.     Stress and the Hippocampus

-     it has been demonstrated that early handling of rat pups reduces the glucocorticoid levels observed in these animals as adults; this is an intriguing finding, as glucocorticoids have been linked to many adverse effects including neural cell loss with aging.

-     subsequent studies revealed decrease cell loss in the hippocampus of rats that were handled as pups, accompanied by fewer memory deficits associated with aging. 

-     in truth, the handling was not critical to this effect, as it was later discovered that the handled pups received more maternal attention than unhandled controls; however, it did provide an interesting link between early experience, stress, and the function of the nervous system.

-     these findings became even more important when it was discovered that the dentate gyrus of the hippocampus of rats, unlike any known other cell in the central nervous system, continue to be produced throughout the lifespan of an individual.  Stress or elevated levels of glucocorticoids block the creation of these new cells, which may account for the hippocampal cell damage that is observed in animals that have been chronically stressed.

Suggested Websites for Chapter 17b:
Stress and Pychosomatic Disorders:
          A look at stress and its effects on general health, from the Brain and Mind site.

نویسنده : S.Hani M.M ; ساعت ۱:۱٠ ‎ق.ظ ; چهارشنبه ۱۸ خرداد ،۱۳۸٤
تگ ها: stress و psychosomatic
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