Micturition

Question 1

How is urine moved through the ureter?

Answer 1

The ureter has SM and undergoes peristalsis.

Question 2

The ureter and kidneys have:

Answer 2

Sensory neurons (think kidney stone, ureter stones).

Question 3

Blockade of ureteral outflow

Answer 3

Increased hydrostatic pressure –> ureteral dilation –> hydronephrosis –> increased risk of ARF

Question 4

Anatomical constrictions of the ureter (4)

Answer 4

Ureteropelvic junction
Testicular/ovarian a. and v.
External iliac a. and v.
Bladder wall

Question 5

Vesiculoureteral reflux

Answer 5

Urine travels back up the ureter –> increased risk of pyelonephritis (infection)

Question 6

Internal urethral sphincter is under __________ control

Answer 6

ANS

Question 7

External urethral sphincter is under __________ control

Answer 7

Somatic

Question 8

Function of the trigone

Answer 8

Senses fullness of the bladder

Question 9

Afferent pathway

Answer 9

Intravesical pressure stretch signals –> sensory nerve fibers (travel w/ pelvic splanchnic n. and hypogastric plexus) –> S2-S4 (sacral micturition center)

Question 10

What fibers sense bladder fullness?

Answer 10

A(delta) fibers (myelinated)
C fibers (unmyelinated)

Question 11

PSNS efferent pathway and NT/R

Answer 11

S2-S4 –> pelvic splanchnic n. –> dextrusor m. constricts –> internal sphincter relaxes

NT = ACh
R = mAChR (M3)

Question 12

Sympathetic efferent pathway and NT/R

Answer 12

L2 –> hypogastric n. –> dextrusor m. relaxes and IS constricts

NT = NE
R = adrenergic

Question 13

Somatic efferent pathway and NT/R

Answer 13

S2-S4 –> pudendal n. –> external sphincter constricts

NT = ACh 
R = nAChR

Question 14

Storage reflex

Answer 14

At the SC

Activated by bladder filling –> sympathetic and somatic outflow –> relaxed dextrusor m. and constricted ES

Question 15

Voiding reflex

Answer 15

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

Question 16

Cerebral cortex’s role (2)

Answer 16

Interprets sensation

Can partially inhibit micturition reflex by clamping the ES.

Question 17

Pontine MC (3)

Answer 17

Gets signals from CC and PAG
Activates ES relaxation and sacral PSNS outflow.
Controls and coordinates S2-S4

Main player in micturition control

Question 18

PAG (3)

Answer 18

Afferent signals from the bladder.
Primary excitation input to the PAG
Higher centers can suppress activation of the PAG