Final answer:
Insulin secretion from the pancreas is triggered by high blood glucose levels and is part of a negative feedback loop that regulates blood glucose. As glucose is absorbed by cells, blood levels drop, signaling the pancreas to reduce insulin output, thus maintaining glucose homeostasis.
Step-by-step explanation:
The regulation of insulin secretion is a prime example of how the secretion of a hormone is controlled by the effects of that hormone's actions. When blood glucose levels are high, such as after eating, the beta cells in the pancreas secrete insulin. This hormone then encourages cells throughout the body to absorb glucose, reducing blood glucose levels. As the cells uptake glucose and utilize it for energy, the blood glucose levels begin to decrease. Insulin also promotes the conversion of glucose to glycogen in the liver for storage and inhibits the liver from releasing glucose back into the bloodstream.
This process of insulin secretion and the subsequent reduction of blood glucose levels exemplify a negative feedback loop. This feedback loop ensures that insulin is not continually released once blood glucose levels have returned to normal, preventing hypoglycemia, which is a 'low sugar' effect. Therefore, insulin secretion is not regulated by external factors alone, nor is it independent of blood glucose levels. Instead, it is directly influenced by the concentration of glucose in the blood.