Adaptive and Regulatory Mechanism

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CONCEPTS OF HOMEOSTASIS AND CONSTANCY OF INTERNAL ENVIRONMENTHomeostasis is the maintenance of a steady state condition (HOMEO = same and STASIS = maintaining ). The body tries to maintain homeostasis in regard to body temperature, blood pH, etc.

Homeostasis is the property of a system either open or closed that regulates its internal environment and tends to maintain a stable, constant condition.

Homeostasis is the process by which organisms maintain a relatively stable environment despite changes in the external environment. Maintenance of a constant internal environment is important for optimal metabolic efficiency. If the internal environment is relatively stable, this allows for a high level of efficiency for the running of cells, such as enzymes having their optimum pH and temperature conditions.Life is a series of chemical reactions. The sum of all chemical reactions is called metabolism. Metabolism is a series of chemical reactions that occur in a specific order. In the human body, thousands of chemical reactions take place. The sequence takes a little under 24 hours and then the whole thing starts over again and occurs each and every day. In other words, everyday, a particular sequence of chemical reactions take place in the body in a precise exacting manner.For this sequence to occur exactly the way its supposed to, the internal environment of the body has to be maintained so that the environment is suitable for these reactions to occur. The chemical reactions will only occur at certain osmotic pressures and at certain concentration of fluids. The chemical reactions need to occur at a specific speed to allow other reactions to occur.

NEGATIVE FEEDBACK CONTROL MECHANISMThe control of cellular function by any hormone depends on a series of reactions working through negative feedback mechanisms. Hormone secretion is dependent on the need of the body for the final action of that hormone. When a body condition starts to move away from the normal range and a specific action or response is needed to correct this change, reaction of the hormone capable of causing the correcting action or response is stimulated until the need (demand) is met. As the correction occurs, hormone secretion decreases (and may halt). This type of control for hormone synthesis is negative feedback because the hormone causes the opposite action of the initial condition change.An example of a simple negative feedback hormone response is the control of insulin secretion. When blood glucose levels start to rise above normal, the hormone insulin is secreted. Insulin increases glucose uptake by the cells, causing a decrease in blood glucose levels. Thus the action of insulin (to decrease blood glucose levels) is the opposite of the condition that stimulated insulin secretion(elevated blood glucose levels).NEGATIVE FEEDBACK

RELATIONSHIP OF ADAPTIVE MECHANISM AND STRESS RESPONSEThe Adaptive Mechanism Concept is a biochemical extrapolation of Hans Selyes pioneering endocrine research into the bodys biochemical response to stress.

Selye has defined stress as the nonspecific response of the body to any demand made upon it. Whenever the body is required to adopt, it must re-establish homeostasis. It doesnt matter in physiological terms whether the stressor is pleasant or unpleasant. What counts is the intensity, duration, and frequency of the demand for readjustment or adaptation.

The central theme of Selyes research indicates that the body responds in a stereotyped fashion to cope with any type of increased demand upon the human machinery. Selye described this response as the General Adaptation Syndrome. In countless experiments, he found that the body reacted in three consecutive ways: 1) by enlarging the adrenal cortex, 2) shrinking the thymus, spleen, lymph nodes and all other lymphatic structures, and 3) by developing GI ulcers. He further postulated that these reactions evolved trough the Alarm Stage, the Resistance Stage, and the Exhaustion Stage.

Selye proposed that an essential feature of the adaptation process is the confinement of stress to the smallest area capable of meeting the requirements of a situation. In the Alarm Stage, the bodys defenses are put on general alert. During the Resistance Stage, the body attempts to concentrate its efforts at the site of demand. This localized effort continues until either homeostasis is achieved or the resources of that area are exhausted. Once local exhaustion occurs, the body draws on the resources of the neighboring tissues or organs, initiating another cycle of the Three Stages of the General Adaptation Syndrome. The stress response is a mechanism by organisms to adapt and overcome a stress stimulus in order to preserve homeostasis. While facilitating survival, the stress response has become associated with a plethora of maladies for modern man suggesting it has maladaptive qualities. In considering the physiological process and its contribution to survival, this essay will argue that stress response cannot be considered a single response to a single system. It needs to be viewed as different variables in different systems with complex interactions between the physiological and psychological. The stress response may be modified by subjective perception of a real or imagined stimulus. This may offer a means of intervening in the stress response to mitigate against adverse consequences. INTRINSIC AND EXTRINSIC FACTORS IN ADOPTION AND DISEASE CAUSATIONIt is quite true that environment has a direct impact on those living in it and many diseases are the outcome of mans maladjustment to his environment. The factors which affect human health and cause disease, can be divided into two categories:

1. Intrinsic or Internal factors2. Extrinsic or External factors

The factors such as malfunctioning of the body parts, hormonal imbalances, malfunctioning of immune system and genetic disorders which exist within the human body, are called Intrinsic Factors. The disease caused by intrinsic factors is called organic diseases or metabolic diseases. Some examples of diseases caused by intrinsic factors are: Heart attack, kidney failure, cataract, diabetes mellitus, etc. The factors such as malnutrition, disease causing microorganisms, environmental pollutants, use of tobacco, alcohol and narcotics, which exist outside of the human body, are called Extrinsic Factors. Some examples of diseases caused by extrinsic factors are Kwashiorkor, Goiter, Cholera, Tetanus, etc.