Final answer:
Blood sugar is regulated by a negative feedback loop, wherein insulin and glucagon help to maintain blood sugar at stable levels. Conversely, positive feedback loops amplify the initial stimulus, like the production of milk during breastfeeding.
Step-by-step explanation:
Blood sugar levels are regulated by a negative feedback loop. In response to higher insulin levels, glucose is transported into cells and liver cells store glucose as glycogen, resulting in a drop of glucose levels in the bloodstream. This process of reducing blood sugar when it gets too high is characteristic of a negative feedback mechanism. Similarly, when blood sugar levels are too low, the body releases glucagon which causes the liver to convert stored glycogen into glucose and release it into the bloodstream. If blood sugar control were by a positive feedback loop, it would lead to increasingly extreme and potentially dangerous levels of blood sugar.
The process of feeling full after a meal and the halting of erythropoietin release when there are enough red blood cells in the bloodstream are also examples of negative feedback. In contrast, an example of a positive feedback loop in human physiology is the production of milk by nursing mothers, whereby the act of breastfeeding stimulates more milk production.