What happens when we sleep?

Description about the different sleep phases and what happens to the body when we sleep.
1 - Light sleep: We fall asleep, the muscles relax and the Thalamus in the brain makes sure that we cannot move and avoid sleep walking
2 - Slow Wave Sleep : Slow oscillations in the brain. We are in deep sleep, almost oblivious to outside stimuli. During this phase there is a consolidation of memory and a downscaling to save energy in the brain. Body temperature drops by a couple of degrees and kidneys are stimulated by ADH that makes us not want to go pee and regulates blood pressure. (poor sleep leads to more cardiovascular disease and renal failure). Cortisol decreases reducing brain excitability and stress, cytokines are produced that help the body fight infections.
3- REM sleep: the "dream stage" Memory reorganisation, emotional regulation, prepares the brain for the next day, increases procedural learning