system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is happening to my body/brain when I'm trying to wake up and I'm groggy?

My blood is flowing, my eyes are open, so what isn't working properly during those first few minutes after waking up that makes a person groggy?
gpt
Your brain is filled with cells called neurons. In between these neurons are fluid channels that carry nutrients to the cells and carries waste out. During sleep your neurons shrink to about half their normal size. This allows these fluid channels to work much more efficiently. Unfortunately, it also makes your neurons function less efficiently until they regain their normal size in the morning.