The graph shows the blood-glucose levels and insulin levels of
an individual. 50 25 Glucose Insulin 0+ 00 12 16 24 04 08 20 Time
(h) Blood-glucose levels are controlled by a feedback loop that
involves the hormone insulin. Which of the following statements
best explains the role of insulin in this feedback loop?
1.) Insulin controls the blood-glucose level in a positive
feedback loop. As the level of blood glucose rises above a normal
set point, the level of insulin increases to raise the
blood-glucose level even higher.
2.) Insulin controls the blood-glucose level in a negative
feedback loop. As the level of blood glucose rises above a normal
set point, the level of insulin increases to raise the
blood-glucose level even higher.
3.) Insulin controls the blood-glucose level in a positive
feedback loop. As the level of blood glucose rises above a normal
set point, the level of insulin increases to lower blood-glucose
back to the normal level.
4.) Insulin controls the blood-glucose level in a negative
feedback loop. As the level of blood glucose rises above a normal
set point, the level of insulin increases to lower blood glucose
back to the normal level.