Insulin and its role in the human body

Insulin is a hormone that is synthesised and secreted by the pancreas. The Pancrease is a 15 cm long, fish-shaped gland, situated behind the stomach and across the back portion of the abdomen. Most parts of this large gland are occupied with the normal processes of digestion through the pancreatic enzymes. These are proteins that speed up chemical reactions thus facilitating digestion. But one small part, known as the tail of the pancreas, has a conmpletely different function. It belongs to the endocrine glandular system which is a group of organs that releases hormones directly into the blood. It secretes or releases two hormones, insulin and glucagon.

Insulin comes from tiny cells in the pancreas called beta cells. These cells reside in isolated masses of tissue called islets (EYE-lets). They secrete insulin in sufficient quantity as and when needed. Because of this secretion, blood sugar remains within the normal limits.

All cells in our body need energy in order to function normally. This energy is derived from carbohydrates, proteins, and the fats present in the food that we eat. The carbohydrate, which mainly comes from cereals and starch such as wheat, rice, fruit, etc. is converted by the body into glucose, or simple sugar, and absorbed into the blood stream. This glucose is the main source of energy for all the body cells. Excess glucose is stored in the liver and muscles as a compound called glycogen.

When we eat, the pancreas responds by secreting insulin into the blood stream. This insulin in the blood is responsible for carrying glucose from the blood into each of the million cells that make up the body's various tissues and organs. It helps in converting the glucose into energy within the cells, thereby releasing energy required for maintaining the vital body functions. When insulin is either inadequate, absent, or abnormal, it is difficult for glucose to enter the cells and provide the energy needed.

Apart from helping glucose enter the cells, insulin is also involved in the process of storing glycogen in the liver and muscles, where it is stored as a source of reserve energy. In between meals, when the cells need energy, glycogen stored in the liver and the muscles is converted back into glucose and used by the cells.

Normally, pancreas releases insulin proportional to the amount of food we eat. The beta cells monitor blood glucose levels regularly and release the amount of insulin necessary to use the glucose in the blood. In diabetes, the pancreas either does not produce insulin, or produces too little, or produces defective insulin that cannot be used by the body.

Thus, the blood glucose cannot be used effectively by the cells and excess glucose cannot be stored in the liver.