Insulin Secretion and Effects Insulin is released in response to increased

Insulin secretion and effects insulin is released in

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Insulin Secretion and Effects Insulin is released in response to increased blood levels of glucose, as occurs after a meal. The secretion of insulin decreases as blood levels of glucose decrease. Insulin has many target tissues and therefore exerts widespread effects: Insulin helps transport glucose into most cells. Without insulin, glucose remains outside the cells, thereby depriving the cell of its fuel. (The liver and brain require glucose for their metabolic needs but do not require insulin for the transport of glucose across the cell membrane.) Insulin is the only hormone that lowers blood glucose! Insulin helps control carbohydrate, protein, and fat metabolism in the cell. Insulin stimulates the breakdown of glucose (glycolysis) for energy and stimulates the liver and skeletal muscles to store excess glucose as glycogen (glycogenesis). Insulin also increases the transport of amino acids into cells and then stimulates the synthesis of protein from the amino acids. Finally, insulin promotes the making of fats from fatty acids. Diabetes mellitus is often defined as a lack of insulin. However, some diabetics with adult-onset, or type 2, diabetes mellitus have excess insulin (hyperinsulinemia) and are still hyperglycemic. insulin binds to the insulin receptors on the cell membrane. 1. The insulin receptors are damaged? The damaged receptors cannot respond to the insulin, and the person becomes hyperglycemic. The hyperglycemia then triggers the release of additional insulin and the person becomes hyperinsulinemic. 2. There are a diminished number of receptors? The number of insulin receptors on the membrane can increase or decrease. Obesity and lack of exercise can cause the number of insulin receptors to decrease. This means that obese people can secrete plenty of insulin, but their cells cannot respond to that insulin 3. Excess fat (adipose) tissue secretes hormones that oppose the effects of insulin? Some cytokines antagonize insulin, causing a state of insulin resistance. Hyperglycemia. Excess glucose in the blood is called hyperglycemia. This condition is caused by two factors. The first is the inability of glucose to enter the cells, where it can be burned for energy. Failure to move the glucose into the cells causes it to accumulate in the blood. The second is the making of additional glucose. In the absence of insulin, the body makes glucose from protein (gluconeogenesis). The excess glucose cannot be used by the cells and therefore accumulates in the blood Glucosuria or glycosuria. Glucose in the urine is called glucosuria or glycosuria. The hyperglycemia causes excess glucose to be eliminated in the urine. Polyuria. Excretion of a large volume of urine is called polyuria. Whenever the kidneys excrete a lot of glucose, they must also excrete a lot of water. Glucosuria therefore causes polyuria.
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