Homeostatic control of the blood glucose by insulin and glucagon is achieved by which of the following?
1) A decrease in blood glucose stimulates glucagon; an increase in blood glucose stimulates insulin
2) An increase in insulin lowers blood glucose; an increase in blood glucose stimulates glucagon
3) An increase in blood glucose stimulates glucagon; a decrease in blood glucose stimulates insulin
4) An increase in glucagon lowers blood glucose; a decrease in insulin lowers blood glucose