system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Can someone explain our physical reactions to something amazing or surprising (e.g. our jaw dropping, getting the "chills," our hands going over our head)?
gpt
Adrenaline. When a cascade is released it triggers a fight or flight response which can lead to involuntary subconscious actions. Covering the head protects it. Opening the mouth helps increase oxygen availability in case you have to run. Goosebumps go back to our primitive roots of putting up the hackles on our fur to make us look bigger. Like cats do.