system
Given the following post, respond as if you're commenting on Reddit:
human
How, exactly, do we fall asleep?

What is the process going on in our brain? How do we get to that "off" switch?
gpt
We don't really fall asleep so much as we fade asleep, and scientifically speaking, it's hard to pinpoint exactly where wakefulness ends and sleep begins. The process of sleep starts before you're in bed, even. As you get towards the end of the day or your usual sleep time, your body temperature starts to drop, hormone levels change to get your body ready for sleep, you start to feel a bit drowsy. When you get into bed, your brain starts to take in less and less external information and your brain activity slows, shifting from active and awake beta and gamma waves to slower alpha wave to even slower theta waves. Heart rate and breathing rate slows but your muscles are still somewhat active. This is considered the first stage of sleep, NREM 1. What's interesting is that if you woke someone up in NREM 1 sleep, they may not recognize that they were asleep. In the next stage, NREM 2, you would see theta brain waves with sleep spindles and K-complexes. Your muscle activity drop and you are nearing the point where you are unaware of the outside world. This is the point where someone would be considered fully asleep.