Endotherm

All mammals, birds, and some fish are endothermic, meaning they create their own heat. They create their own heat incidentally as a result of their internal body functions. Sometimes though we cannot create enough heat in extreme cold, or we become too hot in extreme heat, that is where shivering and sweat come in. Endotherms are also known as warm-blooded, the opposite of ectotherms, who cannot create their own heat, and are known as cold-blooded.