Tag Archives: diabetes

Homeostasis – Regulation of Blood Glucose Levels

isle of langerhans

The pancreas is an important exocrine and endocrine gland located between the stomach and small intestine. It has two important roles (1) as an exocrine gland it releases digestive enzymes into the duodenum that aid in the break down of food (2) as an endocrine gland it releases insulin and glucagon into the bloodstream.

Insulin is produced in the beta cells of the islets of Langerhans in response to the stimulus of rising blood glucose levels. Insulin travels in the bloodstream and binds with receptor sites on the cell membranes, resulting in a cascade of events dependent on the cell type. In liver cells, for example, glucose in converted to glycogen, fat and carbon dioxide.

Glucagon is produced by alpha cells in the islets of Langerhans in response to the stimulus of falling blood glucose levels. Glucagon travels in the bloodstream and binds to receptor sites on liver cell membranes, resulting in the breakdown of stored glycogen into glucose. This results in an increase in blood glucose levels.

These two hormones act to regulate the body’s blood glucose levels, maintaining an average concentration of 5.0 mmol/Litre (between 3.5 mmol/Litre after several hours without food and 7.0 mmol/Litre soon after a meal). This is a negative feedback loop, as the response results in a change in the stimulus in the opposite direction. A person with diabetes is unable to regulate their own blood glucose levels without external intervention – it may be that their body does not produce enough insulin, as in Type 1 Diabetes mellitus.

Connecting with GTAC to learn about Diabetes

GTAC_polycom

 

On Monday, our students had the opportunity to connect with Maria and Fran at GTAC to learn about signaling molecules, insulin disorders and diabetes. Fran presented information about how molecules transmit signals across the cell membrane to allow glucose (and other substances) to be absorbed at a greater rate. Students modelled this process using paper cut-outs, showing how the message is passed from the insulin receptor, to the transmission molecules, to the effector molecules (vesicles with GLUT4 glucose transporter molecules attached), which allow more protein channels to be situated in the cell membrane. The normal response is that more glucose is absorbed by the cell, but several disorders can result in glucose not being absorbed, such as Type I and Type II diabetes. Students observed diagnostics on blood samples to determine if test patients are diabetic. They then applied the stimulus response model to learn the effect of insulin on glucose homeostasis and explore the role of insulin in cell signaling.