The document discusses how the hypothalamus regulates body temperature through increasing or decreasing mechanisms in response to heat or cold. In hot conditions, the hypothalamus triggers sweating and vasodilation to cool the body, while in cold conditions it causes piloerection, vasoconstriction, shivering and metabolic heat production to conserve heat. The hypothalamus integrates input from thermoreceptors in the skin and blood to maintain core temperature within a narrow range.