Feedback loops often control mechanisms in the human body. Some mechanisms are controlled by positive feedback loops, while others are controlled by negative feedback loops.

Four mechanisms common in the human body are described below. Which of these is controlled by a negative feedback loop?
(pick more than one)

Low oxygen levels trigger the kidneys to release the hormone erythropoietin, which stimulates the production of red blood cells. As oxygen levels return to normal due to an increased number of red blood cells available to transport oxygen, the kidneys stop making erythropoietin, and red blood cell production declines.
An increase in blood glucose triggers the pancreas to produce insulin, which causes glucose to be stored as glycogen. As glucose levels decrease, insulin production stops, which results in glycogen being converted back to glucose.
A tear in the lining of a blood vessel wall causes clotting to occur as platelets attach to the site of the tear and release chemicals. The released chemicals attract more platelets, which results in more clotting.
When a woman is in labor and uterine contractions begin, her body releases the hormone oxytocin. Oxytocin causes a nerve stimulus, which stimulates the body to produce more oxytocin. This further increases the occurrence of contractions.