Micturition Flashcards
How is urine moved through the ureter?
The ureter has SM and undergoes peristalsis.
The ureter and kidneys have:
Sensory neurons (think kidney stone, ureter stones).
Blockade of ureteral outflow
Increased hydrostatic pressure –> ureteral dilation –> hydronephrosis –> increased risk of ARF
Anatomical constrictions of the ureter (4)
Ureteropelvic junction
Testicular/ovarian a. and v.
External iliac a. and v.
Bladder wall
Vesiculoureteral reflux
Urine travels back up the ureter –> increased risk of pyelonephritis (infection)
Internal urethral sphincter is under __________ control
ANS
External urethral sphincter is under __________ control
Somatic
Function of the trigone
Senses fullness of the bladder
Afferent pathway
Intravesical pressure stretch signals –> sensory nerve fibers (travel w/ pelvic splanchnic n. and hypogastric plexus) –> S2-S4 (sacral micturition center)
What fibers sense bladder fullness?
A(delta) fibers (myelinated) C fibers (unmyelinated)
PSNS efferent pathway and NT/R
S2-S4 –> pelvic splanchnic n. –> dextrusor m. constricts –> internal sphincter relaxes
NT = ACh R = mAChR (M3)
Sympathetic efferent pathway and NT/R
L2 –> hypogastric n. –> dextrusor m. relaxes and IS constricts
NT = NE R = adrenergic
Somatic efferent pathway and NT/R
S2-S4 –> pudendal n. –> external sphincter constricts
NT = ACh R = nAChR
Storage reflex
At the SC
Activated by bladder filling –> sympathetic and somatic outflow –> relaxed dextrusor m. and constricted ES
Voiding reflex
At the brain
Activated by full bladder –> afferent neurons to SC then brain –> activate PSNS outflow and inhibits SNS and somatic outflow –> dextrusor m. contracts and ES relaxes
Cerebral cortex’s role (2)
Interprets sensation
Can partially inhibit micturition reflex by clamping the ES.
Pontine MC (3)
Gets signals from CC and PAG
Activates ES relaxation and sacral PSNS outflow.
Controls and coordinates S2-S4
Main player in micturition control
PAG (3)
Afferent signals from the bladder.
Primary excitation input to the PAG
Higher centers can suppress activation of the PAG
