What happens to your muscular system when you have a really high fever?
The external pyrogens lead to the formation, in the human body, of the secondary pyrogens. It is assumed that, under the action of secondary pyrogens the control point of the thermal control center is changing and perceives the normal body temperature, as being low.
Sympathetic nervous system excitation leads to spasms of peripheral vessels, reducing sweating, increasing the secretion of adrenaline and noradrenaline, of thyroid hormones, which, on the one hand, are limiting the release of the heat and, on the other hand, are increasing the thermogenesis in our body.
The amplification of thermogenesis is get on behalf of catabolic processes, by involuntary contractions of skeletal muscles - muscles' tremors.