system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do humans blush when they are embarrassed?
gpt
Blushing is a reaction of the sympathetic nervous system and part of our “fight or flight” response. When you’re embarrassed, adrenaline is released, speeding up your heart rate and dilating your blood vessels to improve your blood flow and oxygen delivery. In humans, facial veins react to this adrenaline by blushing. But this response doesn’t happen anywhere else in your body, which is why you don’t blush all over.