system
Given the following post, respond as if you're commenting on Reddit:
human
What makes you wake up?

So what makes people wake up naturally? Is it our internal clock or is it just our bodies saying we've had enough rest? I ask this because I've found that sometimes if I go to bed late then I'll wake up earlier than if I went to bed early.
gpt
Your homeostasis sleep drive or pressure for sleep reduces the longer you sleep. After enough time it runs out and you don't feel sleepy. Another thing that helps is your internal clock or circadian rhythm which tells your pineal glands to stop producing melatonin. Melatonin being a hormone that aids sleep.