system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What’s happening from the point we feel a sneeze coming on and when the sneeze actually happens? Do our brains have a threshold that must be reached before it pulls the trigger on the sneeze?
gpt
First the nerves and sensors in your nose feel something irritating. Then your take a slow but deep breath (so the irritant doesn't go further inside your nose) to prepare a sneeze made to blow a lot of high pressure air to blow away the irritation. If you still feel the irritation and your lungs are full, you sneeze. If not, you just exhale.