system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is happening in my body when I'm throwing up?

Throwing up always has steps for me

1. "Wow my stomach is bubbly" 

1. Then I get the initial feeling of 'doom' and that unmistakable lump in my throat

1. "Here it comes" My stomach starts contracting and I begin to dry heave the first couple times

1. Then I'm throwing up. Trying to catch my breath in between hurls. 

What exactly triggers the throwing up and what is going on inside of me when throwing up?
gpt
1. Something has upset your body and your body is warning you not to consume anything new while we sort this out.

2. Your body has decided that extreme measures are needed and is warning you to prepare (evolutionarily - to find a safe space to be incapacitated for awhile).

3. Your digestive system is performing its contractions in reverse. Usually your digestive tract performs nice coordinated contractions from top to bottom to force food down. When you throw up these contractions change direction.

4. Yes, you are now throwning up.