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
Regulating factors the cycle would start over. Therefore, food is a regulating factor in this scenario, as food supply keeps the population at relative equilibrium. All regulating factors are density-dependent, meaning they keep populations at equilibrium by counteracting fluctuations in population size per unit area (or per unit volume for species living within three dimensional environments, such as water). Other regulating factors of the human population at present are drinking water supply, amount of arable land (obviously a more fundamental term for food), air pollution and prevalence of communicable disease. The major regulating factor for the human population in current times is