How is blood glucose maintained in between meals and overnight?

The complete digestion and absorption of a meal can take several hours, depending upon its size and composition. Therefore, carbohydrate or more specifically glucose from that meal may be available for several hours as well. However, once this ends, a new blood glucose scenario begins to take shape. Cells throughout the body will continue to help themselves to glucose in the blood to help meet their energy needs. The net effect is that our blood glucose concentration will begin to decrease. When this happens the pancreas responds again. However, this time it responds by releasing the hormone glucagon into our blood. In addition, epinephrine (adrenalin) and cortisol will promote efforts in different tissue that will help maintain blood glucose levels in between meals.

 

How does gluagon help maintain blood glucose levels in between meals?

Glucagon works in a manner that is generally opposite to insulin. It will labor to increase blood glucose concentration, thereby returning it toward normal levels. To accomplish this, gluca­gon promotes the breakdown of liver glycogen to glucose, which is released into circulation.

 

Glucagon will also promote another activity in our liver that will generate glucose. The process is called gluconeogenesis, which literally means to create new glucose if you read its root words right to left. In this process, certain amino acids, lactate (lactic acid), and glycerol from our circulation will be taken up by our liver and used to make glucose. Like the glucose generated from glycogen breakdown, this glucose can also be released into our blood to maintain blood glucose levels.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

How does epinephrine (adrenalin) help maintain blood glucose levels during fasting?

During a fasting period, a little epinephrine (adrenalin) is released into circulation from our adrenal glands. Among epinephrine’s many roles will be its ­influence upon the liver and skeletal muscle. It will support the effects of glucagon in the liver that were just mentioned. In skeletal muscle, the slightly elevated epinephrine will lightly promote the breakdown of glycogen to glucose. Contrary to the glucose produced from the breakdown of liver glycogen, this glucose is not released into the blood. Rather, this glucose becomes a supportive energy source for those muscle cells while fat is the major energy source. However, when this glucose is used for energy in those cells, a little bit of lactate may be produced. This lactate can enter circulation, reach the liver, and be converted to glucose. This glucose can then be released into the blood. Therefore, our skeletal muscle can modestly contribute to maintaining our blood glucose concentration during fasting.