How much sleep do we really need?

If I got absolutely no sleep the night before, I can not function the next morning. If I get between 2-4 hours of sleep, I’m fine. 4-7 hours and I cant function. More then 7 and i’m fine. Why is this?

Also, if I had my way i would sleep 10 hours a night.

No matter how little sleep i get, i absolutely CAN NOT fall back asleep once I’ve been woken up. I’m unable to take naps no matter how tired I am. It takes me quite a while to fall asleep.

Im abnormal, I know.

I can not for the life of me fall asleep with the TV or music on. I have to fall asleep to some background sound ie) a fan