Anna often finds that she becomes drowsy in the afternoons. The warmer her classroom is, the harder she finds it to stay awake. Why does warmth make her more tired?

Her metabolism reduces so as to reduce the amount of heat the body is producing. This reduces the risk of overheating/hyperthermia. During metabolism, approximately 60% of the energy produced is released as heat. This coupled with the high temperatures in the classroom increases her core temperatures. Due to the reduced metabolism, Anna feels sleepy since the body processes become slow in a homeostatic feedback response.