system
Given the following post, respond as if you're commenting on Reddit:
human
[ELI5] What happens to our brain the exact moment we fall asleep?

Like, how in one moment we are awake and in the other unconscious? What precisely happens that triggers it?
gpt
It’s not really such a sharp transition, you generally drift to sleep and the current theory is that the thalamus (basically a relay station between your senses and your brain) gradually stops transmitting information from your senses to your brain.