Page 126 - Clinical Biochemistry

(D) Acts on cells in the hypothalamus: to reduce appetite.

In each case, insulin triggers these effects by binding to the insulin receptor. a transmembrane
protein embedded in the plasma membrane of the responding cells.
Taken together, all of these actions result in:
• The storage of the soluble nutrients absorbed from the intestine into insoluble, energy-rich

products (glycogen, protein, fat)
• A drop in the level of blood sugar.
2-Alpha Cells
• The alpha cells of the islets secrete glucagon, a polypeptide of 29 amino acids.
• Glucagon acts principally on the liver where it stimulates the conversion of glycogen into
glucose ("glycogenolysis") and fat and protein into intermediate metabolites that are ultimately
converted into glucose ("gluconeogenesis")
• In both cases, the glucose is deposited in the blood.
 Glucagon secretion is:
• Stimulated by low levels of glucose in the blood.
• Inhibited by high levels of glucose & amylin.
 The physiological significance of this is that glucagon functions to maintain a steady level
of blood sugar level between meals.
 Injections of glucagon are sometimes given to diabetics suffering from an insulin reaction
in order to speed the return of normal levels of blood sugar.
6- The adrenal Glands
• There are 2 adrenal glands located on the top of each kidney.
• Inner part secretes adrenaline, outer part secretes aldosterone and cortisol.
• They maintain salt levels in the blood, maintain blood pressure, help control kidney
function, control overall fluid concentrations in the body.