Define positive feedback systems and describe why they are not necessarily beneficial to organisms. Include a description of the changes associated with severe blood loss and circulatory shock to substantiate your answer.

Concepts to Consider: Positive feedback systems are rare, but when they occur, the response to the stressor leads to a further deviation from the steady state or set point. That is, the response intensifies rather than reverses the initial change and therefore they do not maintain homeostasis. Hemorrhage is an example of a stressor that can result in a significant blood loss. The loss of blood causes a drop in blood pressure, and less blood will circulate back to the heart. Heart function declines along with a decrease in cardiac output (volume of blood per contraction of the heart). The overall result is therefore a further drop in blood pressure associated with this decrease in heart output.