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How are blood glucose levels regulated in humans?

Blood glucose homeostasis involves maintaining the levels of blood glucose within a very narrow limit around a set point (90mg 100cm-3). This is done via hormonal regulation. On one hand, insulin which is a peptide hormone, is produced by the beta cells of the pancreas (islets of Langerhans). It is released by the pancreatic beta cells when blood glucose levels rise, such as after ingesting a carbohydrate-rich meal. Insulin binds onto cellular receptors. It causes glycogenesis (conversion of glucose to glycogen) in lover and skeletal muscle, the conversion of glucose into fat (triglycerols) within adipose tissue as well as increasing cellular uptake of glucose. These processes reduce blood glucose levels back to set point. 

However, glucagon, a hormone produced by the alpha cells of the pancreas increases blood glucose back to set point when blood glucose levels have dropped such as when a person is exercising. It increases the rate of glycogen breakdown (glycogenolysis), the release of fatty acids from adipose tissue to be used to make glucose (gluconeogenesis) and also increasing the rate of fat break down (lipolysis). This is to provide cellular glucose to be broken down during respiration to produce ATP molecules. 

There are other hormones also released to increase blood glucose such as adrenalin, the ''fight or flight'' hormone produced by the adrenal medulla. It increases glycogenolysis, and fatty acid release. Cortisol, another hormone, produced in the adrenal cortex, causes amino acids (small building blocks of protein) to be released from skeletal muscle and fatty acids to be released from adipose. Amino acids and fatty acids are converted to glucose via gluconeogenesis. 

 

 

 

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