system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does pain (i.e. migraines, hard hits to the head) cause the body to vomit?
gpt
Nausea is pretty much the body’s go-to solution when feeling bad. Extreme pain? Puke. Concussion? Puke. Nervous about your final exam? Puke. It’s essentially a safe guard against poisoning, where your monkey-brain tells your stomach to empty its contents in case you’ve eaten something you shouldn’t have.

In some cases of more severe concussions, it can also be a direct result of swelling in the brain, where the «bruise» you got when you hit your head causes a swell in your not-too-spacious cranial vault. This might result in pressure on the part of your brain that causes vomiting, known as the vagus nerve.