Blood Sugar
The term "blood sugar" refers to the amount of glucose in the bloodstream. Glucose enters the bloodstream through the intestines as part of the digestive process. The body makes immediate use of most of the sugar that we ingest, but it keeps a small portion in reserve in the liver. The glucose in the liver is called glucagon and acts as an emergency backup when the body has an immediate need for sugar. Sugar that is not used for energy, or stored as glycogen, is stored on the body as fat.
Blood Sugar Uses
Glucose is the raw material for adenosine tri-phosphate (ATP), the body's primary fuel. The mitochondria inside the cells converts glucose into ATP through a process called the Krebs cycle. The body relies on a hormone called insulin to get the glucose into the cells. All glucose-processing cells have little keyholes called insulin receptors. When insulin sits on these receptors, it acts like a key and unlocks the cells, allowing the sugar to enter. Inside the cell, the mitochondria convert the glucose to ATP--similar to the way a refinery converts crude oil to gasoline. The cells then use ATP to fuel all of the processes of the organs to which they are attached. For example, the heart muscle cells use ATP to contract the heart.
Blood Sugar Levels
All of the body's processes run 24/7, so the body needs a constant supply of glucose and ATP. The normal blood sugar range is between 70 and 150mg, and levels are usually lower upon waking and higher after eating. The brain and the pancreas both monitor blood sugar levels; as the levels fall closer to the bottom of the range, the brain signals the pancreas to release a hormone called glucagon. Glucagon stimulates the liver to release glycogen into the blood, for emergency energy, and the pancreas releases insulin to put the glycogen into the cells. Glycogen is only a temporary fix so the brain also initiates the hunger response, which causes us to eat and raise our blood sugar levels. The body may take a couple of hours to convert all of the glucose from each meal into ATP. It ultimately depends on how quickly we digest the food, what type of food it is, how much we eat and our activity levels.
