system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we get tunnel vision before we pass out?

A few months ago when I was in the gym I dropped a weight on my finger, there was alot of blood and I even though I'm not a squeamish person I passed out in the bathroom after laying there feeling really cold for about 3 minutes. Before I passed out I saw loads of blue dots like sparkles, and then darkness started filling the edges of my vision until I could only see through a tiny gap about the size of a cup, then my vision completely went but I was still partially concious as I remember waving my hand in front of my face and seeing complete blackness even though my eyes were open.

This was the first and only time I've ever passed out by the way.
gpt
This is your body going into shock. When it does go into shock, all of the blood heads toward the major organs in the core of your body and away from your appendages. This causes blood loss in your brain which causes you to pass out.