Final answer:
Hyperthermia occurs when the body's temperature is too high, and hypothermia occurs when it's too low. Both conditions can be lethal as they lead to a failure of the body's normal functions, particularly affecting the central nervous system.
Step-by-step explanation:
The serious health situation that occurs when the body is unable to regulate its temperature is known as hyperthermia when it's too high, and hypothermia when it's too low. Controlled hypothermia can be induced clinically to reduce metabolic rates during certain medical procedures. However, both excessive hyperthermia and hypothermia can be deadly if they occur naturally, leading to the cessation of normal body functions starting with the central nervous system. Additionally, the body's thermostat is located in the hypothalamus, which plays a critical role in temperature regulation.