Describe the regulation of blood glucose level.

The glucose level is regulated in pancreas by negative feedback loop, which means that when there is too much glucose, it is removed from the blood, and when there's too little, it is released into the blood.

When there is too much glucose, beta cells in the islets in the pancreas are activated and produce hormone insulin. What insilin does is that it minds to receptors on muscles and liver and stimulate the uptake of glucose from blood. The uptaken glucose is then either used in cell respiration (muscles) or stored in a long-term form as a glycogen (liver). Thus the level of glucose decreases to the desired level.

On the other hand, when the glucose level is too low, glucose needs to be replenished in the bloodstream. Low level glucose activates the alpha cells, which produce glucagon and release it into the blood. What glucagon does is that it stimulates breakdown of glycogen stored in the liver and converts it to glucose (reverse of what insulin does in liver). Glucose is released and the glucose level in the blood increases up to the required amount.