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November 22, 2005 1:28 PM   Subscribe

Help me understand the mechanics of peeing.

So, what's going on in there when we pee? I imagine the bladder is emptying of urine, but that air probably isn't replacing the volume of liquid being expelled, so my bladder is simply deflating/crumpling up inside me? And what's with the squeezing? (I assume that's my prostate I'm squeezing when I cut off the flow, right? So what do girls squeeze with, since they don't even have a prostate?) How come we squeeze multiple times during a "session" to cut off the flow? Is there some physiological cue? I really can't explain why I stop-and-start multiple times instead of letting it out in one long stream, so I was wondering if there was a scientific explanation (or well-informed speculation) on why people do this. And one seems to increase the frequency of the squeezing the closer to being done one is. What's up? Please clear up my anatomical/mechanical befuddlement.

Any insight on the mysterious "delicious shivers" would also be welcome.
posted by evariste to Health & Fitness (33 answers total) 3 users marked this as a favorite
Your blood pressure drops when you pee, so if you already have low blood pressure, you might pass out.

The more you know (TM)
posted by cmonkey at 1:30 PM on November 22, 2005

I think the muscles that cut off the flow are the Kegels. Or is that just the name of the excercise to strengthen them? The prostate is a gland, not a muscle. You have no voluntary control of it.
posted by spicynuts at 1:31 PM on November 22, 2005


And it's the pelvic floor muscles (desribed by Dr. Kegel) that help you stop the flow. That's about all I know.
posted by gaspode at 1:33 PM on November 22, 2005

More Wiki. The muscles are the Pubococcygeus or "PC" muscles that Kegel came up with exercises for.
posted by SuperNova at 1:35 PM on November 22, 2005

Your Urinary System and How It Works.

Also, post-micturition convulsion syndrome. The idea is that it is probably due to the parasympathetic nervous system, but no one is really sure.
posted by jenovus at 1:35 PM on November 22, 2005

i always thought the shivers were because you were removing a considerable volume of heat from your body, which shivers to warm back up again. however now that i think about it, your internal temperature shouldn't change when you pee, but maybe it's some weird reflex.

so much for insight!
posted by sergeant sandwich at 1:38 PM on November 22, 2005

And do any other males find that they can only really truly empty their bladder when standing?
posted by Good Brain at 1:53 PM on November 22, 2005

You can't squeeze with your prostate: it's a gland. It'd be like doing pushups with your thyroid.
posted by gleuschk at 2:05 PM on November 22, 2005 [1 favorite]

I have to say that, as a male, I've never gotten the whole stop-and-start thing that I hear so often in the men's room. I don't do it myself, except to squeeze out the last bit.
posted by Turd Ferguson at 2:17 PM on November 22, 2005

Here's some info on "the shiver" via The Straight Dope.
posted by ktrey at 2:21 PM on November 22, 2005

Good Brain-not really, though it's still more psychologically satisfying to stand.

gleuschk-ha! OK, point taken.
posted by evariste at 2:22 PM on November 22, 2005

gah. already linked above.
posted by ktrey at 2:23 PM on November 22, 2005

Turd Ferguson-I'm pretty sure I don't do it for the joy of it, but I wonder if the stop-and-go squeezing is a learned behavior.
posted by evariste at 2:29 PM on November 22, 2005

Did you teach yourself NOT to do it? Or did you just never start?
posted by evariste at 2:31 PM on November 22, 2005

I've noticed my neighbor's dog does stop-and-go squeezing too.
posted by forallmankind at 3:20 PM on November 22, 2005

And why am I bladder shy?
posted by Captaintripps at 3:27 PM on November 22, 2005 [1 favorite]

I don't do the starting and stopping thing either. Must be a learned behaviour.
posted by cmonkey at 4:17 PM on November 22, 2005

I find that my bladder gets really empty when I pee sitting. I never stop-and-go pee, unless I am intentionally working on my sex muscles.
posted by dhammala at 4:18 PM on November 22, 2005

cmonkey, I marked forallmankind's answer as a best answer because of urine-scent-marking territory. Humans don't do it, but we probably evolved from something that did, hence the behavior. I bet that has a lot to do with it.
posted by evariste at 4:29 PM on November 22, 2005

I don't start and stop, either. I have a relatively shy bladder. And while I had always thought piss-shivers were an exclusively male domain, it turns out my wife sometimes has them. I'm not actually convinced they're the exact same thing, though.
posted by five fresh fish at 5:01 PM on November 22, 2005

"And why am I bladder shy?"

That's a good question, too. It seems like it would be best explained in terms of some intersection of sociology and psychology. But it might be even more complicated because in the last year as I've been using some different medications, I've found quite a bit of variability in terms of ability to get that stream going, or not. Not each time, but in general where there's a correlation with med changes.

What it feels like when I can't start peeing is that I'm pushing up somewhere with the bladder but I'm not relaxing my pubococcygeus muscles. That's what it feels like, but maybe something else is happening. But it's very frustrating. When it's a "shy bladder" because I'm peeing in public, then it feels that way. But, with some meds, I'll have the same problem at home with no one around! It feels exactly like I'm not letting myself pee. And that sort of disagreement between different parts of my body really annoys the hell out of me.
posted by Ethereal Bligh at 5:05 PM on November 22, 2005

No start-and-stop here but for the very end.

Anybody else get forgetful about that last bit when they're in a hurry?

posted by cortex at 5:12 PM on November 22, 2005 [1 favorite]

Women don't stop and start, for the record.
posted by arcticwoman at 5:34 PM on November 22, 2005

Women don't stop and start, for the record.

Unless we sneeze, or are "working the sex muscles."
posted by heatherann at 5:55 PM on November 22, 2005

Women don't stop and start, for the record.

Unless distracted, or really tired, or exercising, or just doing it for the heck of it.
posted by fish tick at 7:39 PM on November 22, 2005

I noticed that with girl-dogs, too, they just squat and let it all out. A boy has to wander all over the place leaving his mark.

So I'm not surprised human girls don't do it.
posted by evariste at 7:51 PM on November 22, 2005

Sometimes women start and stop—when I know someone else is in the room and fear that they're somehow paying attention, I often have to distract myself so I don't tighten up and do the start-and-stop thing.
posted by limeonaire at 7:59 PM on November 22, 2005

This topic is monstrously complicated. Anyone who claims to be able to answer your questions fully in under an hour is ignorant.

I'm not going to try to do it here, but I would point out that the answers to your questions are known and reside in urologic and neurologic textbooks.
posted by ikkyu2 at 9:12 PM on November 22, 2005

The detrusor muscle is the muscle that contracts automatically when you want to pee. You pushing is mostly you contracting your abdominal muscles to increase intra-abdominal pressure and put pressure on the bladder. Men have two sphincters, an internal one, before the prostate, and an external one, after the prostate. Women only have one.
posted by gramcracker at 11:54 PM on November 22, 2005 [1 favorite]

Dear Abby or Ann Landers recommended that women make a temporary stop or pause "midstream" so to speak in order to tone the necessary muscles against the onset of incontinence. Needless to observe, they were not sponsored by Depends.
posted by Cranberry at 12:06 AM on November 23, 2005

Good brain - I'm totally that way... if I'm taking a dump, I often find that I have to do a bit of a stand-up-and-squat over the toilet when I finish in order to make sure all the urine drains. Otherwise I'll be seeing some serious leakage when I tuck "Lil' Anti" back into the boxers.
posted by antifuse at 2:08 AM on November 23, 2005

Most people don't consciously start and stop their flow while peeing. Like Turd Ferguson said, men are more likely to squeeze the pelvic floor (pubcoccygeus) towards the end of peeing because this helps drain the last few drops of urine from the penile urethra, and reduces the annoying dribble after peeing (post-micturition dribble).
Women have in the past been recommended to start and stop as a way of strengthening the pelvic floor. This is no longer generally recommended, because it is thought to increase the risk of not completely emptying the bladder.
As for "bladder shyness", I cured myself of it using a recommendation from a Nicolson Baker novel. He suggests imagining yourself liberally peeing on the face of the intimidating person at the next urinal over. Works for me.
posted by roofus at 6:35 AM on November 23, 2005

After the stream is spent, I also do the squeeze to get out the last, but also a thumb-and-index iris-like closure around the base and push any remainder out like getting the remainder out of a toothpaste tube. Haven't had the 'dimespot' as it were, in ages.

I very rarely get shivers, though, but sometimes occurances of hairs-stand-on-end. I am curious (I have not read any of the links yet) if what I recall hearing that (1) the adrenaline glands are near or related to kidneys is true, that the adrenaline action causes (2) the hairs-stand-on-end reaction (like a fight-or-flight response) and since (3) hairs-stand-on-end events also occur when the surface temperature of the skin is lower than inside -- as well as shivers also being an attempt to raise the temperature of the skin by friction/flexing, then the (4) shivers are a result of kidney-adrenaline interaction rather than temperature drops? I sure write long sentences.
posted by vanoakenfold at 10:05 AM on November 23, 2005

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