A firefighter, a long-distance runner, and a student pulling an all-nighter for an exam all experience significant challenges. The firefighter faces the intense heat and danger of a blaze, the runner pushes their body to its physical limits during a marathon, and the student endures prolonged mental exertion and sleep deprivation. According to the principle that the body's physiological reaction to stress is nonspecific, which of the following statements best describes the internal bodily responses of these three individuals?