Final answer:
In a negative feedback loop, an increase in a controlled variable above its set point leads to actions that decrease it, with hormone secretion increasing to decrease the variable, and decreasing to prevent it from increasing. The response is 'decrease, increase.' This is how the body maintains homeostasis, contrasting with positive feedback which amplifies conditions.
Step-by-step explanation:
In a negative feedback loop, an increase in a controlled variable above its set point may lead to an increase in the secretion of a hormone that helps to decrease the value of the controlled variable, and a simultaneous decrease in the secretion of a hormone that helps to increase the value of the controlled variable. Therefore, the correct answer to the question is 'decrease, increase.'
Negative feedback is used to maintain homeostasis in the body. For example, when blood glucose levels rise, the pancreas releases insulin, which helps to lower the glucose level. Conversely, if blood glucose levels are too low, the pancreas releases glucagon to increase them. In this manner, the concentrations of hormones in the blood are maintained within a narrow range. This is opposed to positive feedback, which amplifies a response, potentially moving a system farther from the set point, and is far less common in the body due to the risk of creating extreme conditions.