Interactions between the Liver and Pancreas

Explain the control of blood glucose concentration, including the roles of glucagon, insulin and α and β cells in the pancreatic islets. Distinguish between type I and type II diabetes.

Homeostasis The human body stays within normal limits for many physiological variables including: –Blood pH (~7.4) –Body temperature (~98.6°F) –Blood glucose level ( mg of glucose per 100 mL of blood)

Negative Feedback The processes that sense changes in the body and activate mechanisms that reverse the changes in order to restore conditions to their normal levels This is the type of response system that your body uses to maintain a homeostatic range for your blood glucose levels

How does it work? Since the blood coming into the liver from the hepatic portal vein carries all dissolved nutrients absorbed from the small intestines, and it is the liver’s job to filter those nutrients, the liver will be chemically told what to do by hormones secreted by the pancreas The pancreas secretes the hormones insulin and glucagon into the bloodstream depending on the levels of glucose in your blood The hormones are secreted directly into the blood and are therefore from endocrine glands called islets of Langerhans

Cells in the islets of Langerhans have chemoreceptors which are sensitive to glucose

Blood Glucose Level Too High β (beta) cells in the islets will produce the hormone insulin and insulin is secreted into blood All cells chemically communicate with blood, so all cells will be chemically told that there is too much glucose; this results in: –Body cells open protein channels in plasma membranes to allow glucose to diffuse in –Hepatocytes (liver cells) absorb glucose and convert it to glycogen which is stored in liver cells –Muscle cells also convert glucose to glycogen and then store it in their cells

Blood Glucose Level Too Low This usually occurs when someone has not eaten for many hours or exercises vigorously for a long time α (alpha) cells in the islets produce and secrete via endocrine glands the hormone glucagon The glucagon circulates in the blood and results in: –Hydrolysis of glycogen (polysaccharide) in liver and muscle cells back into glucose (monosaccharide); this glucose can then enter the bloodstream which increases the blood glucose level

Diabetes A metabolic disorder in which a person does not produce enough insulin (Type I) or the body does not react properly to insulin (Type II) Typically results in hyperglycemia (too much glucose in the blood) Uncontrolled diabetes can lead to the following effects: damage to retina leading to blindness, kidney failure, nerve damage, poor wound healing/gangrene

Type I An genetically inherited autoimmune disease where the body attacks and destroys the β cells so little to no insulin is produced ~5-10% of diabetics have this type and it is usually diagnosed in children and young adults Treatments include insulin injections, and transplants including pancreatic and islet cells

Type II Body has insulin resistance and no longer responds to the insulin as it should Increased risk associated with: obesity, genetic history, lack of exercise, advanced age, and certain ethnic groups including African Americans, Latinos, Native Americans, and Asian Americans Treatments include a balanced diet and increased exercise ( weight loss is the goal ) as well as oral medications to increase the production of insulin or to lower blood glucose level ( typically insulin is not needed unless the diabetes progresses )