(4) Micturition (SD Wang) Flashcards
What is micturition?
How your body gets rid of urine!
What is considered the upper urinary tract?
What is the considered the lower urinary tract?
Upper urinary tract = Kidney & Ureter
Lower urinary tract = Bladder, Urethra
State what type of muscle lines each sphincter
Internal Urethral Sphincter
External Urethral Sphincter
Internal Urethral Sphincter = Smooth muscle
External Urethral Sphincter = Skeletal muscle
What are the three demarcations of the trigone?
(2) Urethral openings
(1) Internal urethral sphincter
Function of the trigone?
Senses “fullness” of the bladder
Clinical Correlations:
Blockade of Urethral Outflow
Caused by?
What results?
Caused by= blockage in ureter
What results= increase in hydrostatic pressure, ureteral dilation, hydronephrosis
Clinical Correlations:
Anatomic Constrictions
Where can this occur?
Where can this occur =
- Ureteropelvic junction
- testicular/ovarian a./v.
- external iliac a./v.
- bladder wall
Clinical Correlations
Vesicoureteral Refulx
What is occuring?
Ureteral openings don’t fully close…
Leading to urine traveling back up the ureter
*Increased risk of pyelonephritis (kidney infection)
Describe the pathway for afferent (sensory) system of the bladder
Intravesical pressure stretch signals –>
Sensory nerve fibers (run w/ pelvic splanchnic n. and hypogastric plexus) –>
S2-S4 (sacral micturrition center)
What fibers transmit bladder fullness signals to the brain?
A (delta) fibers - myelinated
What fibers transmit bladder pain signals to the brain?
C fibers (unmyelinated)
Describe the efferent (motor)
PARASYMPATHETIC
What spinal level?
What nerve?
What does activation of this nerve this cause?
Neurotransmitter?
Receptor?
S2-S4
Pelvic splanchnic n.
Contraction of the detrusor m. and internal sphincter relaxation
ACh
mAChR (M3)
Describe the efferent (motor)
SYMPATHETIC
What spinal level?
What nerve?
What does activation of this nerve this cause?
Neurotransmitter?
Receptor?
L2
Hypograsteric n.
Detrusor m. relaxation and internal sphincter contraction
NE
Adrenergic
Describe the efferent (motor)
SOMATIC
What spinal level?
What nerve?
What does activation of this nerve this cause?
Neurotransmitter?
Receptor?
S2-S4
Pudendal n.
External urethral sphincter contraction
ACh
nAChR
What are the two bladder reflexes?
- Storage reflex
- Voiding reflex
The storage reflex is initiated in the _________
Spinal Cord
What is the storage reflex activated by?
Which causes?
Which then results in…
Bladder filling
Causes sympathethetic and somatic outflow
Detrusor m. relaxed & external sphnicter contracter
What is the Voiding Reflex activated by?
Which causes?
Which then results in…
Full bladder
Afferent neurons to transmit to spinal cord, then brain
Stimulates parasympathetic outflow and inhibits sympathetic/somatic outflow
Detrusor m. contracting and external sphincter relaxing
Where is the voiding reflex primarily occuring?
Brain
Function of the cerebral cortex with bladder reflexes?
Interprets sensation
Can partially inhibit micturition reflex
Function of the midbrain with bladder reflexes?
Contains the periaqueductal gray (PAG)
Receives afferent bladder signals
Primary excitation input to the PMC
Higher brain centers can suppress or stimulate the input of PAG to the PMC
Function of the pons with bladder reflexes?
Contains the central hub of bladder reflexes “pontine micturition center (PMC)”
aka Barrington’s nucleus
Receives signals from the PAG and higher brain centers
Activates external sphincter relax and sacral parasym. outflow to cause micturition
Controls/coordinates S2-S4
D. Pain is paroxysmal
Paroxysmal = intermittent
B. Hydronephrosis
C. Adrenergic receptor antagonist
A. L2 Hypogastric nerves
A. Detrusor m. contraction and internal sphincter relaxation
C. Vesicoureteral reflux
A. Detrusor m. and sphincter working in coordination
C. Cerebral cortex
B. Metastasis to sacrum
C. Sympathetic pathway
A. Urinary frequency
C. Pudendal nerve, voluntary
