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The meaning of Homeostasis.

The tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.


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Fun Facts You Might Have Not None, About Homeostasis.

The concept of homeostasis is widely used, in physiology and psychology, to identify what seems to be a general attribute of living organisms: the tendency to maintain and restore certain steady states or conditions of the organism. An obvious example is that of body temperature, which in the human tends to fluctuate only in a narrow range about the value 98.6° F. When the temperature rises above the normal range, corrective reflexes (perspiration, reduced metabolism, etc.) go into action to restore the steady state. Persistent deviation may initiate other actions (moving into the shade, plunging into water, etc.). If body temperature drops, other corrective actions are observed.

Many bodily steady states follow this pattern. Blood glucose level, blood pH, and osmotic pressure are examples. The key concepts are: an observable steady state that persists over time with minor changes; thresholds above and below this normal range; a sensory input that reports changes in the steady state; and effector mechanisms for restoring the steady state.When a deviation goes beyond either the upper or the lower threshold, energy is mobilized to restore the steady state to its optimal value. Physiologists have been concerned mainly with the reflexes triggered by such deviations, but psychologists have emphasized those homeostatic actions that are seen in learned behavior. Man will exert considerable energy to protect optimal states. He may take restorative action (building a fire when cold) or forestalling action (moving south before winter arrives). The simple reflex level and the complex learned response to homeostatic disturbance are often labeled differently: Stagner and Karwoski (1952) called the former “static homeo-stasis” and the latter “dynamic homeostasis”; Cofer and Appley (1964) used the terms “physiological homeostasis” and “behavioral homeostasis.”


The Systems that Homeostasis Effects.

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Is What We Eat Associated Homeostasis?

To ensure adequate nutrition, it is necessary for the brain to have intrinsic circuitry that regulates the levels of various nutrients in the blood and in the body stores. One could argue that the homeostatic drive for feeding is not intrinsically related to the rewarding aspects of the behavior. However, avoiding or terminating the discomfort associated with hunger provides a strong drive for feeding. In addition, the feeling of contentment that accompanies a full stomach may itself be rewarding, and in the absence of a homeostatic drive to eat, food consumption loses much of its allure (i.e., loss of appetite). Thus, to understand the rewarding nature of food, it is necessary first to understand the brain mechanisms that support the homeostatic drive for feeding. For many years, descriptions of the brain mechanisms for regulating the homeostatic drive to eat were fixated on a model of two opposing cell groups, the lateral hypothalamus driving feeding and the ventromedial nucleus inhibiting it to cause satiety. Although this model contains some useful elements, it was largely exploded by advances in the late 1990s that were based upon the discovery that a systemic hormone, leptin, produced by white adipose tissue during times of plenty, is a necessary (but not sufficient) stimulus for satiety.