system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is actually happening when you stand up too quickly and lose vision momentarily?
gpt
Your blood pressure drops when you sit/lay down so when you stand up too quickly your brain can't get enough blood since Gravity is too powerful to overcome so your body shuts down vision, balance, and hearing to save the brain. That's why some people get dizzy, lose vision, or hear a ringing sound.