Paramedic National Registry Practice Exam 2025 – The All-in-One Guide to Master Your Certification!

Reflex hypothermia occurs when the body's heat regulation mechanisms respond to prolonged exposure to cold, leading to a drop in the core body temperature. In this situation, the body attempts to conserve heat by constricting blood vessels and reducing blood flow to the extremities, which can diminish the temperature in the body's core. Prolonged exposure to low temperatures can overwhelm the body's ability to maintain a normal core temperature, resulting in hypothermia.

The other options suggest factors that affect body temperature differently. Severe dehydration can disrupt thermoregulation, but it primarily leads to heat-related illnesses rather than directly causing hypothermia. Excessive exercise typically raises body temperature rather than lowering it due to increased metabolic activity and heat production. High ambient temperature can lead to heat exhaustion or heat stroke, which are opposite conditions to hypothermia. Thus, prolonged exposure to cold stands out as the most direct cause of reflex hypothermia.