Lecture 37 Flashcards
Where is the pancreas located?
Just posterior to the stomach, has its neck and head in the head and neck is roughly located at the duodenum.
What part of the pancreas secretes insulin and glucagon, which cells are responsible for these two hormones?
The pancreatic islets which are little circular masses on the pancreas (2% of mass) are areas where insulin and glucagon are secreted. The beta cells secrete insulin and the alpha cells secrete glucagon.
What effects maintain homeostasis of glucose levels in the blood?
If the blood glucose gets too high the beta cells detect this and secrete insulin, this causes body cells (fat and muscle) to take in more glucose and the liver to take it up and store it as glycogen. This causes the blood glucose levels to return to normal.
If the blood glucose levels get too low the alpha cells will detect this and secrete glucagon, this causes the liver to break down its glycogen stores and release it as glucose into the blood causing the blood glucose levels to rise.
What are the normal blood glucose levels in the blood?
During fasting 60/80mg/dL is normal (3.3-4.4 mmol/L), within two hours of the postprandiol dip it is from 100-140 mg/dL (5.6-7.8 mMol/L), within hours it will return to the normal set point of roughly 90 mg/dL.
What type of feedback control is glucagon and insulin secretion?
negative feedback as the response to it reduces the stimulus to produce it.
What hormones increase glucose levels in the blood? What hormones decrease it?
Glucagon, growth hormone, adrenaline and cortisol increase blood glucose levels, insulin is the only hormone that decreases it.
How does insulin trigger cells to take in glucose? if this cell were a muscle cell what affects would occur to the glucose and how?
Insulin binds to the target receptors on the cell membrane, stimulating the receptor to become phosphorylated, this stimulates IRS-1 to act on Pl-3kinase which in turn phosphorylates glucose channels (GLUT4) within the cell, these will then move to the cell membrane, allowing glucose into the cell.
In an active muscle cell this glucose will be converted into glucose 6 phosphate by hexokinase and into ATP via glycolysis. if the muscle cell is inactive the glucose six phosphate will be converted to glucose 1 phosphate and then into glycogen via glycogen synthase.
What is insulin resistance? What does this lead to and what are the relative glucose levels in and out of the cell?
Insulin resistance is when the cells become resistant to insulin, this means the insulin doesnt affect the cell as strongly possibly due to malfunctioning insulin receptors or not enough insulin receptors. This causes the cell to not take in much glucose and as such there is low intracellular glucose levels and high glucose levels in the blood.
This leads to type II diabetes as the beta cells will produce more insulin to compensate and will overwork themselves, eventually shutting down.
What is a large factor which causes type II diabetes? How does it do this?
High saturated fat diets will lead to high amounts of saturated fat in the bloodstream, in some cells (such as muscle cells) this will be converted into diacylglycerol in the cell which interferes with the pathway to release glucose channels.
What occurs to the beta cells in type II diabetes? What are the relative insulin levels in the blood?
The beta cells will grow larger in order to secrete more insulin as there will be permanent high blood sugar levels. Eventually this will lead to the beta cells tiring out and stopping production of insulin. This means that insulin levels at the start are extremely high and insulin levels towards the end are low.
What treatment options are there for people with diabetes mellitus?
Type I diabetes patients can only recieve insulin injections as treatment as their beta cells don’t produce insulin (probably because they arn’t there).
Type II diabetes can be treated with insulin injections, drugs which promote insulin release such as incretins and lifestyle changes.
