The concentration of glucose in the blood is regulated by two hormones produced by the pancreas: insulin and glucagon. Insulin is made in the pancreatic islets of Langerhans, in specialized, insulin-producing cells called beta cells. When the pancreas recognizes that the concentration of glucose in the blood is too high (7.5 mmol/dm^3 instead of 5.0mmol/dm^3), it produces insulin in the islets of Langerhans and releases it into the bloodstream. Insulin, a hormone, acts on a homeostatic complex in order to lower blood glucose levels.
Embedded within the cell membrane of body cells, particularly in the intestine, are large numbers of insulin receptors. These receptors are called RTKs (Receptor Tyrosine Kinases) because they function by phosphorylating (hence, a kinase) other intracellular molecules in order to initiate a specific cell response. In the case of insulin, the extracellular (on the outside) alpha-subunit of the protein, which binds insulin in the blood, would be considered the "receptor" portion of the homeostatic complex. Once insulin binds to this, it catalyzes the phosphorylation of the intracellular (inside the cell) beta-subunit of the insulin receptor, which then phosphorylates another protein called the Insulin Response Protein. The Insulin Response Protein then activates the enzyme Glycogen Synthase. This process, from beta-subunit to the Insulin Response Protein to Glycogen Synthase can be considered the "integrating center" portion of the homeostatic complex. Finally, activated Glycogen Synthase converts intracellular glucose into a compound called glycogen, which is insoluble in blood, thus lowering the total blood-sugar concentration. The conversion of glucose into glycogen by Glycogen Synthase is considered the "effector" part of the complex.
The link below provides a good overview of homeostatic controls, the role of insulin, and a graph demonstrating what happens when blood sugar rises.
https://courses.lumenlearning.com/boundless-ap/chapter/homeostasis/
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