system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do our bodies take a while to become fully functional when we first wake up?
gpt
Because the brain wakes up in stages and not all at once. Those stages progress essentially from the back of the brain to the front. The areas in the back are the basics and the ones closer to the front are more complex. That's why we're at first able to stumble around and sort of see things, then maybe mumble a few words and finally have a coherent thought. 

Also factored in is what stage of sleep you're in. If you woke up from deep sleep it's going to take longer to become functional than if you were in light sleep.