How does negative and positive feedback keep a hockey skater alive if he fell through the ice?

Erica O: How does negative and positive feedback keep a hockey skater alive if he fell through the ice?
Two hockey players aer skating on a frozen pond. One skater falls through the ice into the water. Explain how negative feedback can keep the skater who fell in alive. Explain how positive feedback can provide physical assistance to the friend trying to save him.

Answers and Views:

Answer by kirchwey
Two kinds of system protect the skater who went through the ice. The first kind involves the body’s homeostatic system, an array of negative-feedback loops that regulate the internal environment, including core temperature. A reduction in temperature will trigger increased metabolic activity to maintain a healthy temperature. The second kind, vasoconstriction, is not a feedback system but rather open-loop. This reduces heat loss by constricting the blood vessels at the body’s surface. It is triggered by sensed external-environment coldness rather than core temperature reduction.
As for the rescuer, this is more difficult. I suppose you could consider the use of an ice awl a kind of positive feedback. You jam it into the ice in such an attitude that the harder you pull on the awl the deeper it digs into the ice, providing increased resistance to the pulling force.