Blood glucose, also called blood sugar, is one of the parameters that human bodies maintain at near-constant levels in order to thrive. Like variations in body temperature, variations in blood glucose levels cause significant symptoms, and the body employs several compensatory mechanisms to try to regulate glucose levels. Blood glucose levels affect physiology differently, depending upon whether they're high, low or normal.
Cellular Glucose Uptake
Normal levels of blood glucose cause the cells to engage in routine metabolic processes. In a healthy person who eats small, balanced meals consisting of fat, protein and fiber-containing carbohydrate throughout the day, blood glucose levels rarely rise or fall outside the parameters of normal concentrations. In response to normal blood glucose, the pancreas releases small amounts of the hormone insulin, explains Dr. Lauralee Sherwood in her book, "Human Physiology." This signals the cells to take up small amounts of blood glucose in accordance with their energy needs. Body cells utilize the glucose to provide them with energy, while muscle cells and liver cells store the glucose for later use.
Insulin Spike
Under certain conditions, blood glucose levels can rise to very high levels, leading to the effect of significant insulin release. In a normal person, blood glucose levels spike if the person eats a meal very high in sugar and low in fat, protein and fiber. Non-diabetics respond to blood glucose spikes by secreting very high levels of insulin from the pancreas. This, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry," causes cells--particularly fat cells--to take up massive quantities of glucose. Excess glucose is then stored as fat. Fiber, fat and protein help reduce the extent to which blood sugar rises after a meal, and reduce the strength of the insulin signal, leading to less fat storage.
Hormone Release
Glucose also leads to hormonal release effects when levels fall. In such cases, the body works hard to bring levels back into normal ranges. One of the compensatory mechanisms by which it accomplishes this is through pancreatic release of the hormone glucagon. Simultaneously, the adrenal glands release epinephrine. Glucagon and epinephrine work together to signal the liver to sacrifice its stored glucose and release the glucose into the bloodstream, explain Drs. Mary Campbell and Shawn Farrell in their book, "Biochemistry." As the liver releases glucose into the bloodstream, blood glucose levels increase into the normal range. The liver stores a limited amount of blood glucose, so this effect lasts only for a short time. Simultaneously, people feel a variety of symptoms, including hunger, fatigue and dizziness.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
