How does a lack of insulin prevent the cells from using glucose?
The same way not having the right key will prevent you from opening the door. Insulin is a CATALYST. It acts like the "key" to your cells. While insulin is NEEDED to let the suagr into the cell, the insuloin itself is not actually used in the cell. So, if you don't have [enough] insulin in your body, it is just like you left your front door key on the subway -- when you don't have the key, you can't get in.
Diabetes: If too much insulin is taken, why does blood glucose plummet?
What you are asking for is the 'biochemistry' of insulin action :-)Insulin is the HYPOGLYCEMIC HORMONE. In simple terms, what it basically does is reduce blood glucose level.In ideal conditions, this is what insulin does to the blood glucose:-Converts it into instant energy. (50%)There is a process called 'Glycolysis' normally occurring in the cells. The starting product of this cycle is glucose and the end product is energy. This energy is used to used up almost instantly to perform various activities of the body.- Converts it into fat ( 40%)Biochemical process called lipogenesis. -Converts it into glycogen (10%)This occurs by a biochemical process called glycogenesis. Insulin promotes glycogenesis.Now what happens WHEN EXCESS INSULIN IS ADMINISTERED:1) More and more glucose is taken up the cells of the body such as muscle,adipose tissue, leukocytes,mammary glands and the liver.2) Enhanced glycogen production- Insulin PROMOTES the activity of glycogen synthetase ( An enzyme) which thereby leads to increased formation of glycogen. More and more glucose is used up for this.3)Net glycolysis increases- Insulin increases the activity of three main enzymes of glycolysis- glucokinase, phosphofructo-kinase and pyruvate kinase. Net effect is that more and more glucose is utilised for energy production.-Lastly, insulin DECREASES GLUCOSE PRODUCTION. There is a biochemical process called ' Gluconeogenesis' happening in the body by which glucose is synthesized from protein. Insulin INHIBITS the enzymes of gluconeogenesis namely pyruvate carboxylase, phosphoenol pyruvate carboxykinase and glucose-6-phosphatase. Net result is that less glucose is being produced.From the above, we can conclude that insulin,-decreases blood glucose by converting it into instant energy.-decreases blood glucose by shunting it into the cells.-decreases blood glucose by converting it into glycogen.-decreases blood glucose by inhibiting its production.As a result, blood glucose plummets.Hope that answers your question :-)
Why might over secretion of insulin actually reduce glucose uptake by nerve cells?
in type 2 diabetes mellitus, the body is producing enough insulin but the body doesn't respond to the insulin produced so glucose cannot be transported into cells, this is known as insulin resistance. to compensate for the resistance, the pancreas increases the production of insulin hoping that the body might respond...but eventually the pancreatic cells atrophy and there is lack of insulin, similar to what happens in type 1 diabetes..and this is when insulin treatment is indicated.
What causes beta cells to depolarize and release insulin, the efflux or influx of potassium?
When you eat anything which is rich in carbohydrate, the Glucose level increases in your Blood because the Glucose will be absorbed by the villi of the small intestine and transported into the blood vessel. The Glucose molecule will enter the Beta-cells via the GLUT-2 Transport channel. Once it enters the cell, Glycolysis process begins. The Glycolysis (in the cytosol) and the Kreb cycle (in mitochondria) increases the ATP level as compared to the ADP level. The increase in the ATP concentration closes the K+ channel. The K+ channel was initially required for the efflux of the K+ ions to maintain the membrane potential at -70 mV. Once the K+channel is closed, the depolarization of the membrane occurs leading to falling of potential difference to -50 mV.The change in the potential difference will open a voltage sensitive channel called Ca2+ channels. These channels allow the entry of the Ca2+ ions. Once Ca2+ ions enter the cells, the influx of Ca2+ ion will signal the vesicles of insulin in the Beta cells to release the insulin in the blood supply or ECM through exocytosis i.e. the vesicles will release the fuse with the plasma membrane the insulin will be released. The exocytosis is mediated by SNARE proteins which would interact with VDCC (Voltage-dependent Calcium Channels).
Describe the functions of insulin and glucogon in the body?
Insulin is a hormone secreted by cells in the pancreas. The major function of this hormone is to allow glucose to enter the body cells in order to be burned as fuel. If the body ceases to produce this hormone the result is a serious disease known as diabetes. Insulin has three basic categories. There is regular, intermediate, and long acting insulin. These categories help distinguish between its onset of action, peak and duration. All of these having to do with how the insulin is working within the body. Onset refers to the time it takes for the insulin to begin having its effect on the body. Peak is the time it takes for insulin to begin working its hardest to lower the blood glucose. Duration is how long this process lasts. Onset, peak and duration will effect each person differently due to the fact that insulin effects each person differently. Glycogen remaining stored in the liver and muscles after an overnight fast, amounts to about 600 kcal energy. Glycogen reserves can maintain body functions for about one day without new inputs of food. Protein (mostly in muscle) contains a substantial energy reserve of about 25,000 kcal.