Biology A2 question

[D-chris91]

Hi all. My question concerns homeostasis, to be precise negative feedback mechanism of controlling glucose levels in the blood. I understand the mechanism used by the beta cells in producing insulin(i.e. glucose....phosphorylated.....ATP......K-channels close........potential decreases to -50mV........calcium channels open..........vesicles containing insulin are removed by exocytosis). I just don't understand how alpha cells respond to reduced glucose levels in the blood. Can someone explain in similar outline?

[joggingday]

You do not need to know the mechanism for alpha cells. Our A-level text book only contains information about the mechanism for beta cells.

For alpha cells you only need to know that they respond to low blood glucose levels by secreting glucagon which has an effect in liver cells. It causes glycogen to be converted to glucose, fatty acids to be used as a respiratory substrate instead of glucose, and cause glucose to be produced by other substances such as fats. When blood glucose levels are high, alpha cells respond by stopping the secretion of glucagon.