stress (redirected from buccolingual stress)

stress: see strength of materials.

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stress

In phonetics, an emphasis given to a syllable of speech by making it louder than the rest of the word. This emphasis may have no meaning; for example, Czech words are regularly stressed on the first syllable. It may, however, distinguish the meanings of similarly spelled but differently pronounced words; for example, permit is stressed on the first syllable as a noun and on the second as a verb. It may also be applied to a word to express its importance in a sentence. See also intonation.

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stress

In the physical sciences and engineering, the force per unit area within materials that arises from externally applied forces, uneven heating, or permanent deformation. Normal stress refers to the stress caused by forces that are perpendicular to a cross-section area of the material. Shear stress arises from forces that are parallel to the plane of the cross section. Stress is expressed as the quotient of a force divided by an area.

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stress

In psychology, a state of bodily or mental tension resulting from factors that tend to alter an existent equilibrium. Stress is an unavoidable effect of living and is an especially complex phenomenon in modern technological society. It has been linked to coronary heart disease, psychosomatic disorders, and various other mental and physical problems. Treatment usually consists of a combination of counseling or psychotherapy and medication.

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stress

1. such emphasis as part of a regular rhythmic beat in music or poetry

2. Physics

a. force or a system of forces producing deformation or strain

b. the force acting per unit area

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stress [stres]

(biology)

A stimulus or succession of stimuli of such magnitude as to tend to disrupt the homeostasis of the organism.

(mechanics)

The force acting across a unit area in a solid material resisting the separation, compacting, or sliding that tends to be induced by external forces.

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STRESS [stres]

(computer science)

A problem-oriented programming language used to solve structural engineering problems. Derived from structural engineering system solver.

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Stress (psychology)

Generally, environmental events of a challenging sort as well as the body's response to such events. Of particular interest has been the relationship between stress and the body's adaptation to it on the one hand and the body's susceptibility to disease on the other. Both outcomes involve behavioral and brain changes as well as psychosomatic events, that is, changes in body function arising from the ability of the brain to control such function through neural output as well as hormones. One problem is that both environmental events and bodily responses have been referred to interchangeably as stress. It is preferable to refer to the former as the stressor and the latter as the stress response. The stress response consists of a cascade of neural and hormonal events that have short- and long-lasting consequences for brain and body alike. A more serious issue is how an event is determined to be a stressor. One view is to define a stressor as an environmental event causing a negative outcome, such as a disease. Another approach is to view stressors as virtually any challenge to homeostasis and to regard disease processes as a failure of the normal operation of adapative mechanisms, which are part of the stress response. With either view, it is necessary to include psychological stressors, such as fear, that contain implied threats to homeostasis and that evoke psychosomatic reactions. These are reactions that involve changes in neural and hormonal output caused by psychological stress. Psychosomatic reactions may lead to adaptive responses, or they may exacerbate disease processes. Whether the emphasis is on adaptation or disease, it is essential to understand the processes in the brain that are activated by stressors and that influence functions in the body. See Homeostasis, Psychosomatic disorders

Among the many neurotransmitter systems activated by stress is noradrenaline, produced by neurons with cell bodies in the brainstem that have vast projections up to the forebrain and down the spinal cord. Stressful experiences activate the noradrenergic system and promote release of noradrenaline; severe stress leads to depletion of noradrenaline in brain areas such as the hypothalamus. This release and depletion of noradrenaline stores results in changes at two levels of neuronal function: phosphorylation is triggered by the second-messenger cyclic AMP and occurs in the presynaptic and postsynaptic sites where noradrenaline is released and where it also acts; synthesis of new protein is induced via actions on the genome. Both processes enhance the ability of the brain to form noradrenaline when the organism is once again confronted with a stressful situation. Other neurotransmitter systems may also show similar adaptive changes in response to stressors. See Noradrenergic system

Stress also activates the neurally mediated discharge of adrenaline from the adrenal medulla and of hypothalamic hormones that initiate the neuroendocrine cascade, culminating in glucocorticoid release from the adrenal cortex. Thus, the activity of neurons triggered by stressful experiences, physical trauma, fear, or anger leads to hormone secretion that has effects throughout the body. Virtually every organ of the body is affected by stress hormones. The hypothalamic hormone (corticotrophin-releasing hormone) that triggers the neuroendocrine cascade directly stimulates the pituitary to secrete ACTH. In response to certain stressors, the hypothalamus also secretes vasopressin and oxytocin, which act synergistically with corticotrophin-releasing hormone on the pituitary to potentiate the secretion of ACTH. Various stressors differ in their ability to promote output of vasopressin and oxytocin, but all stressors stimulate release of corticotrophin-releasing hormone. Other hormones involved in the stress response include prolactin and thyroid hormone; the metabolic hormones insulin, epinephrine, and glucagon; and the endogenous opiates endorphin and enkephalin. See Endorphins

Of all the hormones in the endocrine cascade initiated by stress, the glucocorticoids are the most important because of their widespread effects throughout the body and in the brain. The brain contains target cells for adrenal glucocorticoids secreted in stress, and receptors in these cells are proteins that interact with the genome to affect expression of genetic information. Thus, the impact of stress-induced activation of the endocrine cascade that culminates in glucocorticoid release is the feedback of glucocorticoids on target brain cells. The effect is to alter the structure and function of the brain cells over a period of time ranging from hours to days.

In the case of noradrenaline, glucocorticoids have several types of feedback effects that modify how the noradrenergic system responds to stress. Glucocorticoids inhibit noradrenaline release, and they reduce the second-messenger response of brain structures such as the cerebral cortex to noradrenaline. Glucocorticoid feedback also affects the serotonin system, facilitating serotonin formation during stress but at the same time altering the levels of several types of serotonin receptors in different brain regions, which has the net effect of shifting the balance within the serotonergic system. Taken together, evidence points to a role of glucocorticoid secretion in leading to restoration of homeostatic balance by counteracting the acute neural events such as increased activity of noradrenaline and serotonin, which are turned on by stressful experiences. Other neurotransmitter systems may also respond to glucocorticoid action. Moreover, the other hormones activated by stress have effects on the brain and body that must be considered. See Serotonin

In general, stress hormones are protective and adaptive in the immediate aftermath of stress, and the organism is more vulnerable to many conditions without them. However, the same hormones can promote damage and accelerate pathophysiological changes, such as bone mineral loss, obesity, and cognitive impairment, when they are overproduced or not turned off. This wear-and-tear on the body has been called allostatic load. It is based upon the notion that allostasis is the active process of maintaining stability, or homeostasis, through change, and allostatic load is the almost inevitable cost to the body of doing so.

Stress hormone actions have important effects outside the brain on such systems as the immune response. Glucocorticoids and catecholamines from sympathetic nerves and the adrenal medulla participate in the mobilization and enhancement of immune function in the aftermath of acute stress. These effects improve the body's defense against pathogens but can exacerbate autoimmune reactions. When they are secreted chronically, the stress-related hormones are generally immunosuppressive; such effects can be beneficial in the case of an autoimmune disease but may compromise defense against a virus or bacterial infections. At the same time, glucocorticoids are important agents for containing the acute-phase response to an infection or autoimmune disturbance. In the absence of such containment, the organism may die because of the excessive inflammatory response. See Immunology

Besides affecting the immune response, stressors are believed to exacerbate endogenous depressive illness in susceptible individuals. Major depressive illness frequently results in elevated levels of cortisol in the blood. It is not clear whether the elevated cortisol is a cause or strictly a result of the brain changes involved in depressive illness. See Affective disorders

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STRESS - STRuctual Engineering Systems Solver. A system for structural analysis problems in Civil Engineering. STRESS was superseded by STRUDL. ["STRESS: A User's Manual", S.J. Fenves et al, MIT Press 1964]. [Sammet 1969, p. 612].