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First, let's start with the definition of homeostasis. Below is the medical definition from Merriam-Webster.Com
The maintenance of relatively stable internal physiological conditions (as body temperature or the pH of blood) in higher animals under fluctuating environmental conditions...
There are several examples homeostasis in the human body. Learn how our bodies maintain a state of homeostasis in order to ensure our survival.
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The body controls the amounts of acids and bases in the blood. When the number of acidic compounds in the blood increases, body acidity also increases. This occurs when someone consumes or produces more acidic compounds or when the body fails to eliminate acidic compounds. When the number of alkaline compounds in the blood increases, body alkalinity increases. Acid-base balance refers to the balance between alkalinity and acidity in the blood, as measured on the pH scale. The kidneys and lungs, along with buffer systems, help control acid-base balance.
The kidneys excrete excess acids and bases. Kidney damage may reduce the ability of the kidneys to excrete these substances, leading to a disturbance in acid-base balance. The lungs control pH levels by excreting carbon dioxide. When a person exhales, the diaphragm pushes carbon dioxide out of the body. The pH of the blood changes when the depth and speed of breathing change, making it possible to adjust blood pH in less than a minute. Buffer systems prevent sudden changes in acidity and alkalinity. These systems consist of weak acids and weak bases that occur naturally in the human body.
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Another one of the most common examples of homeostasis in humans is the regulation of body temperature. Normal body temperature is 37 degrees C or 98.6 degrees F. Temperatures way above or below these normal levels cause serious complications. Muscle failure occurs at a temperature of 28 degrees C or 82.4 degrees F. At 33 degrees C or 91.4 degrees F, loss of consciousness occurs. At a temperature of 42 degrees C or 107.6 degrees F, the central nervous system starts to break down. Death occurs at a temperature of 44 degrees C or 111.2 degrees Fahrenheit. The body controls temperature by producing heat or releasing excess heat.
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Glucose concentration refers to the amount of glucose – blood sugar – present in the bloodstream. The body uses glucose as a source of energy, but too much or too little glucose in the bloodstream can cause serious complications. The body uses hormones to regulate glucose concentration. Insulin reduces glucose concentration, while cortisol, glucagon and catecholamines increase glucose concentration.
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The bones and teeth contain approximately 99 percent of the calcium in the body, while the other 1 percent circulates in the blood. Too much calcium in the blood and too little calcium in the blood both have negative effects. If blood calcium levels decrease too much, the parathyroid glands activate their calcium-sensing receptors and release parathyroid hormone. PTH signals the bones to release calcium to increase the amount of calcium in the bloodstream. If calcium levels increase too much, the thyroid gland releases calcitonin and fixes more calcium in the bones. This decreases the amount of calcium in the blood.
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The body has to maintain a constant internal environment, which means it must regulate the loss and gain of fluid. Hormones help to regulate this balance by causing the excretion or retention of fluid. If the body does not have enough fluid, antidiuretic hormone signals the kidneys to retain fluid and decrease urine output. If the body has too much fluid, it suppresses aldosterone and signals the excretion of more urine.
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Merck Manuals Home Edition: Acid-Base Balance
University of Cincinnati: Body Temperature Regulation
MSN Health: How the Body Controls Blood Sugar
Colorado State University: Endocrine Control of Calcium and Phosphate Homeostasis
The Merck Manual of Medical Information: Water Balance
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