Heat exhaustion occurs when a person's body cannot keep ____.

Heat exhaustion occurs when a person's body is unable to maintain proper temperature regulation due to excessive heat exposure and loss of fluids and salts through sweating. The body's thermoregulation system becomes overwhelmed, leading to an increase in body temperature and causing various symptoms, such as weakness, dizziness, and increased heart rate.

In addition to temperature control, the body also needs to ensure that blood continues to flow efficiently to vital organs. When overheating occurs, blood vessels may dilate and blood flow may be redirected to the skin to cool down, which can compromise blood flow to vital areas like the heart and brain. This dual challenge—failing to regulate temperature and maintaining adequate blood flow—contributes to the onset of heat exhaustion.

In summary, a person experiencing heat exhaustion faces issues with both temperature regulation and blood flow, making the combined answer accurate.