Why can people keep their body temperature normal in a cold environment?

This will start with the internal environment of the human body. There are many forms to maintain human balance, such as inorganic salt balance, body temperature balance, immune system balance and so on. When it comes to human body constant temperature, it is maintained because of the temperature regulation in the internal environment, which is maintained through nerve regulation and body fluid regulation. But when the weather is hot, people's body temperature will not rise too high because of neuromodulation. Its heat dissipation methods include relaxing hair muscles, increasing perspiration and heat dissipation, relaxing blood vessel wall and increasing blood pressure. As for the cold environment asked by the questioner, the body temperature will still be maintained, which is the function of nerve regulation and body fluid regulation. Humoral regulation can increase adrenaline secretion and improve the excitability of nervous system, and thyroid hormone secretion will also increase, but it also involves neuromodulation, that is, thyroid hormone secretion consists of neuromodulation and humoral regulation. There are temperature receptors on human body surface and internal organs. When it is cold, the cold receptors on the body surface are stimulated and the excitement is transmitted to the hypothalamus. There is a temperature regulation center here, which sends out signals to stimulate the release of hormones, thus regulating the rate of metabolism and improving heat production; In addition, there are a series of skeletal muscle contraction reactions (commonly known as trembling), and the hairy muscles on the skin surface also contract, reducing the amount of heat dissipation, that is, the temperature regulation system of the human body achieves body temperature balance by reducing heat dissipation and increasing heat production. In fact, in short, it is the balance between heat dissipation and heat production. When it is cold, the steady state of the human body will make less heat dissipation and more heat production; When it is hot, it is just the opposite. The most essential thing is to thank the benefits of evolution, so that human beings have the most subtle body regulation system!