Final answer:
A fever involves the immune system initiating a response to infection and the nervous system detecting and responding to the change in body temperature to maintain homeostasis.
Step-by-step explanation:
A fever is a response by the body commonly associated with the immune system and the nervous system. The immune system is responsible for the body's defense and launches a fever response as part of its second line of defense to infection. This response can involve raising the body's temperature to help fight off pathogens. On the other hand, the nervous system, specifically the peripheral nervous system, has a role in detecting this increase in body temperature and responding accordingly, which can include shivering to generate heat and maintain homeostasis.