Compare these 2 scenarios. A person has a fever in their body temperature is 40.5°C. Another person has been locked in a hot car and also has a body temperature of 40.5°C. They have hyperthermia. What is the difference between these cases?

In the first scenario body temperature has increased because the hypothalamic setpoint increased. The increase in temperature was brought about by the body increasing heat retention and heat generation. Although the body temperature is higher than normal, the increase can be considered appropriate because the body temperature is at the setpoint. In the 2nd scenario body temperature is higher than the setpoint. The negative feedback systems that control body temperature have been unable to restore it to the desired value. Because the body temperature is higher than it should be this is a case of hyperthermia. Although they both result in an increase in body temperature, fever and hyperthermia are 2 entirely different processes. Another good example of the difference comes from the control of ventilation. If we exercise or increase carbon dioxide generation in the body and we increase ventilation in order to increase carbon dioxide removal. Under those circumstances the amount of carbon dioxide in the blood remains at the normal level. However if we are hyperventilating our ventilation is excessively high, and the levels of carbon dioxide in the blood fall below normal.