Blood Glucose Levels

If the levels of glucose in the blood drop below a normal range the pancreas produces glucogon. This tells the liver to convert the glycogen into glucose. The glucose is then released into the blood and the body detects the increase and switches off the production of glucagon. 

If levels of glucose in the blood increase to a above a normal range the pancreas will produe insulin. The insulin tells the liver to convert the excess glucose into glycogen which is stored in the liver and muscle tissue. The sugar levels then decrease to a normal range and the pancreas stops producing insulin. The body then goes back to monitoring the blood glucose levels. 

The endocrine system is a gland system that releases hormones e.g. the pancreas.

A hormone is a chemical messenger that travels in the blood and has a target organ and produces an effect.