Owen: Micturition Flashcards
___________(male or female) have more bladder infections due to a ________urethra.
female; shorter.
urinary bladder innervation:
Sympathetic efferent innervation is from levels _____. These nerves travel to the ___________ via the _____nerve.
T11-L2; internal sphincter; hypogastric nerve.
urinary bladder innervation:
Parasympathetic innervation is from levels _____. They innervate the _______.
S2-S3. Bladder neck and detrusor muscle for contraction. (efferents travel in pelvic nerves)
The pudendal nerve innervates the __________. It releases _________ to __________ fibers.
external sphincter; Ach; nicotinic. (levels S2, S3)
In filling the bladder, the detrusor muscle is _________ due to _______ innervation. In voiding, the detrusor is __________ due to _________innervation.
relaxed; sympathetic (B3). contracted; parasympathetic (M3).
In filling the bladder, the internal sphincter is _________ due to _______ innervation. In voiding, the internal sphincter is __________ due to _________innervation.
contracted; sympathetic (a1). relaxed; parasympathetic (M).
In filling the bladder, the external sphincter is _________ due to _______ innervation. In voiding, the external sphincter is __________ due to _________innervation.
contracted; VOLUNTARY. relaxed; VOLUNTARY (N).
Mechanism that allows urine to flow through ureters from kidney to bladder?
peristaltic contractile waves.
What features of ureters allow them to stretch to allow urine flow?
smooth muscle and transitional epithelium
How do rugae allow filling of the bladder?
unfold - allow expansion and filling.
Describe how urine reflux is prevented.
the ureter penetrates the bladder wall at an angle to create a flap valve. it is open for easy urine influx when bladder is empty; but when the bladder is full or during micturition, the high intraluminal pressure pushes on the flap valve and prevents reflux. Some people don’t have this angle –> VUR (vesiculoureteral reflux)
Describe the micturition reflex.
bladder filling –> mechanoreceptor activation (stretch receptors activate spinal cord) –>spinal cord AND pontine micturition center (if you can’t conveniently go pee, pons inhibits micturition reflex)
micturition reflex –>detrusor contraction (via PNS) –> increase in uminal pressure –> can i pee now? –> pontine micturition center –> yes –> SNS inhibition, external sphincter relaxation –> voiding
How much volume of pee before urgency sensed? capacity? pain?
300 ml; 500 ml; 700 ml
____________ gradually empty the bladder
pressure waves during voluntary voiding.
Cerebral cortex is mainly _________ in micturition reflex
inhibitory. (but can become excitatory)
how can the cerebral cortex prevent micturition when the reflex occurs?
tonic contraction of the external bladder sphincter (until a convenient time arrives to pee)
What do the cortical centers do to release inhibition when you find a bathroom?
they facilitate the sacral micturition centers to help initiate a mic reflex and
inhibit the external sphincter
How does voluntary urination occur?
You can stimulate the mic reflex:
voluntarily contract the abdomen -> increase pressure on bladder ->extra urine enters the bladder neck and posterior urethra, thus stretching their walls –> stretch receptors are stimulated –> simultaneous stimulation of mic reflex and inhibition of external sphincter
What occurs when the ureteral outflow to the bladder is blocked (i.e. kidney stone)?
Ureter CONTRACTS, hydrostatic pressure increases to 70-80 cm H2O over a period of 1-3 hours.
Pressure gets transmitted in a retrograde fashion to nephrons –> creates a stopped flow condition –> glomerular filtration comes almost to a stop.
Patient complains of severe pain. If block isn’t cleared, noticeable renal dysfunction and even acute kidney failure can occur.
Abnormalities of Micturition:
What happens when sensory nerve fibers are destroyed?
Mic reflex contraction cannot occur.
bladder therefore doesn’t’ empty regularly but instead FILLS to full capacity –> overflow incontinence
Abnormalities of Micturition:
What happens with spinal cord damage ABOVE the sacral region?
first few days to weeks: “Spinal Shock” - mic reflex is suppressed
After time: VOIDING reflex is re-established, but without voluntary control
Abnormalities of Micturition:
What happens with lack of inhibitory signals from the brain with partial damage to the spinal cord or brainstem?
facilitative impulses passing down the spinal cord keep sacral centers in a state of OVER-EXCITATION so that even a small quantity of pee = uncontrollable mic reflex = frequent urination
(patient will have frequent and relatively uncontrolled micturition)
