system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why does changing your body temperature by just a few degrees affect you so much?
gpt
Some proteins and enzymes that are critical to brain and bodily functions are only stable in the narrow temperature band that we've evolved to keep at through complex thermoregulation methods (the proteins and enzymes don't hold their fragile shape when the temp changes a lot, and when they unfold or fold a different way they're effectively useless).  When they break down your brain don't not work so awesome not further any much.  

Your extremities can withstand larger temperature swings, but your brain function starts to break down if you slide more than a few degrees off normal for too long.