Question

In negative feedback systems, what does the term "negative" most likely mean?

1) The feedback system only works when the variable that is sensed (like temperature) drops too low (i.e., in a negative direction)
2) The feedback system only kicks in under sad or depressing (i.e., very negative feeling) circumstances
3) The feedback system senses a departure/change from the set point and then reverses that change (i.e., in the opposite, or "negative," direction)

Answer 1

In negative feedback systems, the term 'negative' signifies the activation of processes that reverse a deviation from a set point to maintain homeostasis. This involves increasing or decreasing physiological variables to counteract the initial change.

Step-by-step explanation:

In negative feedback systems, the term "negative" refers to the action that the system takes to correct a deviation. When a physiological parameter, like temperature or blood glucose level, moves away from a set point, the negative feedback system activates an effector to counteract this change and bring the parameter back into the normal range. This is carried out through a process that may either increase or decrease the stimulus, but ultimately leads to homeostasis by reversing the direction of the change.

An example of a negative feedback loop is the maintenance of blood glucose levels. After eating, glucose levels rise and are sensed by cells in the pancreas, which release insulin to decrease the glucose levels—exemplifying a negative feedback mechanism. Conversely, if glucose levels are too low, glucagon is released to increase them, still following the negative feedback principle.