Homeostasis
The human body's ability to maintain a constant environment is essential to its survival. This capability is referred to as homeostasis. Homeostatic mechanisms keep the body near a set point, based on the sensitivity of central nervous system nuclei, which is an ideal value for that particular person. An example of a homeostatic mechanism is a negative feedback mechanism. Any deviation from the set point is made smaller. This mechanism does not prevent variation, it only helps keep the variation near the set point. Many negative-feedback mechanisms have three components; a receptor, a control center and an effector. A receptor monitors the significance of the variable. The control center is where the set point is established. The effector has the ability to change the variable. The set point varies from person to person. The body usually does not maintain its set point exactly but instead it fluctuates and declines around this point bringing forth a normal range of values. When the body undergoes a physical stressor; such as exercise, a secondary set point is established. The Schneider test measures the recovery rate, the rate at which the body moves back to the original set point once a stressor
This causes a reduction of water loss from the blood into the urine. During exercise, the heart rate/pulse increases therefore causing the blood pressure to increase. Renin acts on angiotensinogen which in turn produces angiotensin I. An adequate blood volume is essential for the maintenance of normal venous return to the heart and therefore for the maintenance of blood pressure. - 80 Jenny: Recline: 110/82 68 Standing: 100/90 68 Exercise: 15 sec. Angiotensin II is a potent vasoconstrictor substance. The renin-angiotensin-aldosterone system and atrial natriuretic hormone, are more important in the maintenance of blood pressure on a long-term basis. It determines the recovery limit of the cardiovascular system.
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