Free Response

Why are negative feedback loops used to control body homeostasis?


An adjustment to a change in the internal or external environment requires a change in the direction of the stimulus. A negative feedback loop accomplishes this, while a positive feedback loop would continue the stimulus and result in harm to the animal.

Why is a fever a “good thing” during a bacterial infection?


Mammalian enzymes increase activity to the point of denaturation, increasing the chemical activity of the cells involved. Bacterial enzymes have a specific temperature for their most efficient activity and are inhibited at either higher or lower temperatures. Fever results in an increase in the destruction of the invading bacteria by increasing the effectiveness of body defenses and an inhibiting bacterial metabolism.

How is a condition such as diabetes a good example of the failure of a set point in humans?


Diabetes is often associated with a lack in production of insulin. Without insulin, blood glucose levels go up after a meal, but never go back down to normal levels.

On a molecular level, how can endotherms produce their own heat by adjusting processes associated with cellular respiration? If needed, review Ch. 7 for details on respiration.


Animals are capable of thermal uncoupling when they need to generate heat to maintain their body temperatures. In this process, an uncoupling protein provides a channel in the inner mitochondrial membrane that allows protons to leave the lumen without moving through the ATP synthase. This generates heat rather than chemical energy as the final product of cellular respiration.