Environmental conditions around an organism are constantly changing. Temperature changes, food and water supplies change, and many other things can change. The organism is still able to maintain a fairly consistent internal balance of chemicals and processes and is able to compensate for these changes. This ability of the organism to self-regulate in the face of variable conditions is knows as homeostasis. Blood-sugar regulation in mammals is an example of a biological homeostatic response.
All mammals are able to regulate their blood-sugar levels. Sugar, or glucose, is the body's main form of energy. Cells use it to perform all their important functions. Without adequate and steady supplies of glucose delivered to cells in the blood, the body would not function properly and could even die. Yet even during times of inadequate food intake, the body is able to maintain consistent levels of blood sugar.
After a large intake of sugars, the pancreas is the organ that senses high levels of glucose in the blood. High levels can be damaging, causing damage to blood vessels which may lead to nerve damage and heart and vision problems. This is called diabetes. When levels are high, a healthy pancreas secrets insulin, which tells the cells to store the excess sugar in the cells for later use, thereby restoring blood-sugar levels back within a normal range to maintain homeostasis.
During fasting, the bodies of mammals are able to maintain consistent blood-sugar levels for 24 hours or more. If blood sugar drops too low, the organism can experience weakness, loss of functions and even death. The pancreas again is the organ that senses that blood-sugar levels have dropped. It releases a molecule called glucagon, which tells cells to release their stores of glucose back into the blood. This mechanism restores blood-sugar levels to a normal range and the organism is able to compensate for these changes.
In order to maintain blood-sugar levels and homeostasis, the organism has mechanisms that work together through feedback systems. Homeostasis mechanisms work together, simultaneously or in succession, in order to rectify imbalances in the internal system and keep the organism alive and functioning despite external changes. Blood-sugar regulation is an example of cells, tissues and organs working together to compensate for change.
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