Based off this pic:
External urinary sphincter: inhibits (via pudendal nerve) Hypogastric nerve: ฮฑ1 receptor โ contracts internal urethral sphincter โ inhibits Pelvic nerves Correct! M3 receptor โ contracts detrusor muscle Pudendal nerve: inhibits (Nictonic receptor) โ contracts external urethral sphincter โ inhibits
External urinary sphincter inhibits (via pudendal nerve)
Hypogastric nerve ฮฑ1 receptor โ contracts internal urethral sphincter โ inhibits
Pelvic nerves Correct! M3 receptor โ contracts detrusor muscle
Pudendal nerve: inhibits (Nictonic receptor โ contracts external urethral sphincter โ inhibits
Here is my summary of the picture/video that was posted:
There are 3 pathways involved in peeing:
Pelvic n. (aka pelvic splanchnic n.) sends parasympathetic fibers to deltrusor to contract --> squeeze bladder and pee.
Hypogastric n. sends sympathetic fibers to the deltrusor to relax, as well as the internal sphincter to contract --> hold back pee
Pudendal n. sends somatic fibers (under conscious control) to the external sphincter to contract --> hold back pee
In this question, the patient's bladder is filling up so much that it's forced to overflow. That means there is a problem with scenario 1 - damage to pelvic n. so that he can't squeeze his bladder even when it's super full.
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.
pelvic nerve--> increases voiding urine, m3 receptor, parasympathetic hypogastric nerve--> increases urinary retention, sympathetic, beta 3 and alpha1 receptors. pudendal nerve--> not part of micturition, its a somatic component and has a nicotinic receptor.
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/
I'm still confused, where is this guys problem occuring? Is that he is unable to urinate, or that he has overflow incontinence? Getting lost in these nerves.
submitted by โhungrybox(1277)
hyoscyamine posted this great pic below