Insulin and Glucagon

What is diabetes mellitus?

A disease in which the body does not produce or respond properly to insulin. When blood glucose levels rise, cells are unable to take up enough glucose to meet metabolic needs.

What disorder can result from disruptions in the glucose homeostasis pathway?

Diabetes mellitus.

Why is maintaining a balanced blood glucose concentration important?

Glucose is a major fuel for cellular respiration and a key source of carbon skeletons for biosynthesis.

What are symptoms of diabetes?

High blood glucose level, the need to urinate excessively, increased thirst and hunger, and tiredness.

Where are insulin and glucagon produced?

In the pancreas in cell clusters called islets of Langerhans. Each islet has alpha cells, which make glucagon, and beta cells, which make insulin.

What two hormones are responsible for regulating the concentration of glucose in the blood?

Insulin and glucagon.

Describe Type I Diabetes.

The immune system destroys the beta cells of the pancreas, limiting the ability of a person to produce insulin. This is insulin-dependent diabetes. This form of diabetes is usually genetically caused and is apparent in children.

What are the two types of diabetes?

Type 1 and Type 2.

Describe the feedback loop when blood glucose levels fall below the set point.

When blood glucose levels fall, alpha cells of the pancreas release glucagon into the blood. This cause the liver to break down glycogen and release glucose back into the blood. As a result, blood glucose levels rise.

When is insulin released and when is glucagon released?

Insulin is released when blood glucose rises above the set point while glucagon is released when blood glucose falls below the set point.

What are the target cells for insulin and glucagon?

Insulin- all body cells (except the brain) Glucagon- liver

What are the affects of insulin and glucagon on their target cells?

Insulin- stimulates target cells to take up glucose from the blood; slows glycogen breakdown and inhibits the conversion of amino acids and glycerol into glucose in the liver Glucagon- signals to liver cells to increase glycogen hydrolysis, concert amino acids and glycerol to glucose, and release glucose into the bloodstream

Describe Type 2 Diabetes.

Target cells fail to respond normally to the insulin that is produced. They are not able to take up glucose from the blood. This is insulin-independent diabetes. This form of diabetes is usually caused by poor health and is apparent in adults over 40.

Describe the feedback loop when blood glucose levels rise above the set point.

When blood glucose levels rise, beta cells of the pancreas release insulin into the blood. This causes the body cells to take up more glucose from the blood stream and the liver cells to store glucose as glycogen. As a result, blood glucose levels decline.