Overview
Homeostasis is the process through which an organism’s body attempts to regulate itself to some baseline of stable balance, essentially forming a negative feedback process in response to either internal or external changes. This contrasts with allostasis, in which the body predicts that a change will happen and proactively adjusts itself in anticipation to preserve some kind of baseline equilibrium. Examples of homeostasis include:
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Thermoregulation: The hypothalamus of the brain will respond to rising temperatures by signaling the sweat glands to release moisture and blood vessels to dilate (vasodilation). When body temperatures fall, the hypothalamus signals the body’s muscles to shiver and create heat while narrowing blood vessels (vasoconstriction).
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Blood Glucose Regulation: When glucose levels rise after eating food, the pancreas releases insulin, which signals to the liver that it should absorb glucose out of the blood. When fasting, exercising, or avoiding eating for any other reason, the pancrease releases glucagon instead, which signals to the liver that it should released stored glucose into the blood.
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Osmoregulation: If you become dehydrated, the brain releases antidiuretic hormone (ADH), which tells the kidneys to reabsorb water. That causes urine to become more concentrated and appear darker. When drinking more water than your body needs to maintain a balance with its dissolved salts, the brain decreases the ADH it releases so that the kidney pushes out water, and urine becomes clearer through dilution.