Question about REM Cycles

I have a little question. I know that when you go to sleep at night, it takes you about 90 minutes to get to the first REM stage which lasts 10 minutes. Through the night the N-REM decreases and the REM increases. It can reach 45 minutes. Now, what happens after I wake up? Is the N-REM continuing to decrease and REM to increase? It stays the same? If it stays the same then why do we have another 90 minutes of N-REM when we go again to sleep in the evening?:?

This goes for each and every night if you have a regular sleep patern. In the beggining 90 somewhat minutes N-REM sleep and a little REM sleep and with each sleep cycle the REM sleep increases.

Good question that I don't have the answer to. I'm curious about that myself. When waking up at an early hour for a WBTB does this ratio continue to change before you actually go back to sleep? I'm curious if anyone has the answer.

Noone?