What are the main two systemic effects of cold on the body?

• A. Vasodilation and increased metabolic rate
• B. Vasoconstriction and slowing of metabolic rate
• C. Dehydration and tachycardia
• D. Sweating and vasodilation

Answer: (B)

When the body meets cold, the two main systemic aims are to preserve core temperature and to generate heat. First, vasoconstriction constricts the small blood vessels in the skin, which minimizes heat loss to the environment and helps keep the core warmer. Second, heat production ramps up. The body increases metabolic rate to generate more warmth, primarily through shivering—a rapid, involuntary muscle activity that boosts heat production—and, in some individuals, nonshivering thermogenesis in brown fat. So the key combination is vasoconstriction plus an increased metabolic rate to generate heat. The idea of slowing metabolic rate would actually hinder heat production, which is not how the body responds to cold.