Final answer:
Insulin and glucagon indeed form a negative feedback circuit to regulate blood glucose levels, ensuring homeostasis; therefore, the statement is true.
Step-by-step explanation:
The regulation of blood glucose levels by insulin and glucagon is indeed an example of a negative feedback circuit. When blood glucose levels rise, the pancreas secretes insulin, which facilitates the uptake of glucose by cells and stimulates the liver to convert glucose into glycogen, reducing blood sugar levels. Conversely, when blood glucose levels fall, the pancreas secretes glucagon to stimulate the liver to convert glycogen back into glucose, thus increasing blood sugar levels. This self-regulating mechanism ensures that the body maintains homeostatic glucose levels in the blood. Therefore, the statement that insulin and glucagon work together to regulate blood glucose levels in a negative feedback circuit is true.