system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is there serotonin in snake venom if that chemical is the chemical that makes us happy?
gpt
Your body repurposes the same chemicals for multiple uses.

Serotonin is used in the brain to modulate your mood, but it’s also used in the circulatory system to control blood vessel constriction and blood clotting.

The snake doesn’t much care about your mood, but it does want to blow up your circulatory system with a huge dose of chemicals that interfere with normal behavior.