Sunday, March 18, 2012

Residency stories: Scared peeless

Attending: "I can't remember, what is the innervation of the bladder? S1? S2?"

Resident: "I don't know."

Me: "It's S2-4 for parasympathetic and voluntarily control, but the sympathetic control comes from T10-12." (I had just been studying for the boards.)

Attending: "Oh. And what does the sympathetic part do? Does that make the bladder relax?"

Me: "Sympathetic is for storage, parasympathetic is for peeing."

Attending: "Oh wow, I think you just helped me pass my PM&R recertification exam."

Resident: "So if that's true, how come when someone gets scared, they pee in their pants?"

Me: "Uh... I don't know..."

Resident: "Because being scared elicits a sympathetic response, right?"

Me: "I don't know. Let's google it."

Attending: "You think it's on google?"

Me: "Yeah, it's autocompleting for 'why do you pee when scared'."

We actually never figured it out. Google was surprisingly unhelpful.


  1. This is what I found: Note that some people urinate (parasympathetic response) when they are very scared (sympathetic system is
    dominant). This is a case of shock, where the sympathetic system becomes overwhelmed in your brain. Urination
    and defecation during extreme stress will still help a person escape a predator, due to the unwanted odor or
    surprising the predatory so the prey can escape.

  2. I asked this same question of my physio prof back in basic sciences. She pretty much said the same thing as Klára. It's not well understood but it's thought to be that the sympathetics overwhelm the brain.

  3. And now I can't remember why men get erections when they are hanged by the neck. And the mnemonic Point (P) and shoot (S). Didn't you do a blog post on this a while back?

  4. It's because the first response released in any stressful event is a parasympathetic response, then shortly thereafter sympathetic takes over.

    It's not actually one or the other it's about which is dominant, and for a brief period of time parasympathetic firing occurs first prior to sympathetic domination.

    Thus, when you are extremely scared you may briefly wet yourself and your "heart stops" but then shortly after you no longer have the urge to urinate and your "heart races"

  5. OMDG: Yeah, that post is one of my top 5 most popular posts:

  6. ok, from my understanding:

    Micturition reflex can be modulated by frontal cortex...& the Pontine micturition center (PMC) in the pons acts as a relay station to the innervation of the bladder.....

    Emotion, sympathetic response etc can have an effect on the PMC, activation of PMC (e.g. fear) causes relaxation of autonomic urinary sphincter & contraction of detrusor muscle...hence you Pee...:)

  7. I think I just learned more on bladder innervation reading this post & comments than I did in our 12 week Neuro block..

  8. my prof told me 2 weeks ago that it was an error of the sympathetic're not actually supposed to pee.

  9. We covered recently in physio that in a situation of "hopeless fear" that the parasympathetic system is predominant which is why there's is micturition and defecation. So like Kiara said, if you see a predator and soil yourself, hopefully you'll be less appealing haha.

  10. I agree with Houmd.The first part of the response is parasympathetic (brief) followed by sympathetic
    Initially it causes increased GI motility, defecation, sexual arousal (remember that is parasympathetic),
    Then sympathetic takes over and you are fine