Blood sugar level several interacting systems, of which hormone regulation is the most important. There are two types of mutually antagonistic metabolic hormones affecting blood glucose levels: These hormones are secreted from pancreatic islets which are bundles of endocrine tissues. There are four types of pancreatic islets, alpha (A) cells, beta (B) cells, Delta (D) cells and F cells. Glucagon is secreted from alpha cells, while insulin is secreted by beta cells. Together they regulate the blood-glucose levels through negative feedback, a process where the end product of one reaction stimulates the beginning of another reaction. In blood-glucose levels, insulin lowers the concentration
Achim Peters at an appropriate level. This goal is achieved in healthy individuals by allocating (diverting) energy from the body. The "Selfish Brain" theory represents a further development of already existing theories on the organization of the energy supply within the human organism. Blood sugar and fat deposition feedback systems constitute a complex system for regulating the intake of nutrients which is controlled by a hypothalamic center. The "Energy on demand” system for energy supply to the brain is seen as a supraordinate instance of this setup, which exerts control over the organs that regulate the blood sugar and fat feedback loops.