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NBME 21 Answers

nbme21/Block 1/Question#34

A 30-year-old man develops urinary incontinence 2 ...

Pelvic nerves

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eacv  here is a video for ilustration https://www.youtube.com/watch?v=US0vNoxsW-k +  




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submitted by neonem(262),

The sacral micturition center is 1 of 3 components of micturition reflex (other 2 are from pontine reticular formation and cerebral cortex). Sacral mict center = S2-S4 spinal cord level traveling from ventral white matter in the Pelvic nerves, responsible for bladder contraction via the cholinergic nerves (think it acts on the M3 receptor in the bladder detrusor?). If you lose these nerves (i.e. in pelvic fracture), will result in overflow incontinence.





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submitted by yo(26),

surprisingly good explanation and picture found on this site. something along the lines of micturination reflex (aka bladder is full and you piss reflex) is gone so the afferent fibers carrying the signal that the bladder is full aren't working. those fibers are carried in the pelvic nerves

ttps://www.toppr.com/guides/biology/excretory-products/micturition/

yo  if still confused, a better explanation can be found here https://courses.washington.edu/conj/bess/urination/urination.html +  
hyoscyamine  i found this image to be helpful in remembering which nerves do what on which receptor. https://i.ytimg.com/vi/JwaeWXhklio/maxresdefault.jpg +2