Poopsinurinals: So your body has these muscles called internal and external sphincters. They act like these rubber bands around your rectum and your urethra (where pee comes out). You can control the external sphincters but can’t control the internal sphincters. The feeling that you need to pee or poop comes from the internal sphincters saying “hey we need to go” to your brain and then they relax to let said pee or poop out. The clinching feeling when you’re trying to hold it in is your external sphincters, which you can control. When you’re sleeping/awake these sphincters are constantly contracted but if the internal sphincters relax, then your brain will wake you up because you have to go.
peanutjesus: I know, kinda disgusting topic, but I’m genuinely curious after waking up this morning in a bit of a panic. Haha.
Sunny_August94: REM sleep puts your body into a paralysis when the cycles that tells you you are hungry or need to go to the bathroom swing around. Prevents you from waking up or having your body go through it’s natural awake rhythms. When you are intoxicated your body can’t go into REM sleep as easily which is why you have a terrible sleep and can sometimes wake up to a lovely wet bed!
Source: a lot of psychology and neuroscience courses
Slydruid: The bladder and rectum have stretch receptors in them that are a “warning” (alarm) and let your conscious mind know that your ready to go. Both your urethra and rectum have muscles under your control that allow you to relax and go.
DrunkNotThatFlexible: Anti-diuretic hormone (ADH) is certainly a factor. ADH levels are supposed to increase at night to prevent urination during sleep. Sometimes this system takes a while to develop in children, making bedwetting more likely [1]. Similarly, disruption of normal daily fluctuations of ADH can lead to bedwetting in the elderly [2]. Alcohol inhibits the release of ADH by the pituitary gland, causing increased production of dilute urine and potentially leading to dehydration and/or bedwetting [3].
[1] https://myhealth.alberta.ca/Health/pages/conditions.aspx?hwid=hw211268&
[2] https://www.ncbi.nlm.nih.gov/pubmed/1997638
[3] https://www.ncbi.nlm.nih.gov/pubmed/7573805
Edit: Cortisol is the primary “alarm” hormone, but cortisol doesn’t really have anything to do with urination. The amount of urine produced is controlled ADH, which doesn’t really have anything to do with waking up. Urinary retention depends on the coordination of these two hormone levels (high ADH low cortisol at night, high cortisol low ADH during the day).
Warrenwelder: We’re not supposed to do that?