What causes heat stroke?

Heat stroke is primarily caused by the body's inability to regulate its temperature effectively. When exposed to high temperatures, especially in combination with high humidity, the body's thermoregulatory mechanisms become overwhelmed. Under normal conditions, the body cools itself through sweating and increasing blood flow to the skin, but in heat stroke, these mechanisms fail. As a result, the body temperature rises to dangerously high levels, often exceeding 104 degrees Fahrenheit (40 degrees Celsius). This extreme heat can lead to cellular damage, affecting the brain and other vital organ systems, which can result in serious health complications or death if not addressed swiftly.

The other options, while related to heat and hydration in different contexts, do not directly explain the primary mechanism behind heat stroke as effectively as the ability to regulate body temperature. Excessive moisture in the air can contribute to the risk of heat-related illnesses but does not cause heat stroke on its own. Low blood pressure and excessive hydration (although it can lead to other issues) are not the main factors leading to the condition of heat stroke.