How Glucose Level in the Blood is Maintained?
Pancreas has special bundles or clusters of cells called islet of Langerhans, named after the discoverer Langerhans. Two types of cells exist in islet of Langerhans; alpha cells and beta cells. The alpha cells play their role in increasing glucose level by secreting a hormone Glucagon. While the beta cells take part in decreasing blood glucose level with secretion of Insulin hormone. Both hormones are secreted in blood stream for their action. Glucagon stimulates production of new glucose by liver and the conversion of complex sugar molecules to glucose from its reserves; glycogen and fat. It acts on liver, skeletal muscles and other body organs to produce glucose for elevating glucose level. On the other hand, insulin stimulates to convert glucose from blood stream to fat and glycogen, as a reserve for future use. This decreases the glucose level in blood. Glycogen is for short term storage and fat is stored for long term use.
When we eat some food containing carbohydrates as a chief component, our glucose level in the blood is raised. This happens because glucose and other nutrients are extracted from food by our digestive system, and are incorporated in blood. Similarly kidneys during urination also tend to incorporate glucose in blood stream by extracting glucose and other nutrients from water or any liquids we take in. Fasting, physical hard work and exercise tends to use glucose and blood glucose level is decreased. This decrease in glucose level is detected by our body and activates the alpha cells in pancreas to play their role. Now the alpha cells stimulate new glucose formation and produce glucagon which stimulates glycogenesis which is the conversion of glucose reserves to glucose and releases it in blood stream.
Now the question arises that how is glucagon and insulin secretion controlled? When blood glucose level is decreased and glucagon is secreted, which elevates the glucose level to an optimum value. After this, a slight increase in glucose inhibits further secretion of glucagon. Same is the case with insulin secretion. In addition, both glucagon and insulin are complement to each other as they take part in regulating each other's secretion after a decrease or increase in blood glucose level. Adrenal gland plays its role for providing necessary glucose to us to fight or flee. With various other processes such as increased heart rate or dilation of pupils, blood glucose level is also increased to help in fight and flight response. After fight or flight, in 'rest and digest' condition though there is no significant increase needed. Thyroid provides the substrates for cellular respiration; glucose and oxygen. So it also increases glucose a little bit. Despite of these functions of adrenal gland and thyroid, major regulatory organ in our normal routine is pancreas.
Now when the insulin formation in our body is decreased, our blood glucose level is failed to be regulated. Glucose level is increased and we need external insulin to sustain; this is the most common disease known as Diabetes Mellitus-I or Juvenile Diabetes. In some other cases, though insulin is sufficiently provided by pancreas but response of the cells under control of insulin is decreased or diminished. This is a more alarming disease known as Diabetes Mellitus-II or Maturity Onset Diabetes. Blood glucose level may also be disturbed in some other diseases. For example, in Addison's syndrome, due to deficiency of a specific hormone, excessive secretion of sodium ions and water in blood is resulted leading to hypotension and weakness. Along with this, blood glucose level is decreased. In another disease, Cushing's syndrome, glucose level is increased along with other major symptoms of the disease such as formation of pores in bones and poor wound healing.
In short, human body has been designed with special features that set our body at a normal operating condition. A little disturbance of these is covered by the body itself, saving ourselves from many disturbances. In case of serious problems, we should refer a medical doctor instantly, to have a good care of our body systems.
Useful External Resources
To know about the importance of controlling blood sugar go to www.health.ny.gov
How to keep blood sugar in check >>: www.urmc.rochester.edu
Edited by: Rajesh Bihani ( Find me on Google+ )