Function of the Bladder Flashcards
what is the minimum rate of urine production?
1ml/min
what is the maximum rate of urine production?
20ml/min
what do stretch receptors in the bladder wall do?
as bladder fills they generate signals to tell brain how full it is
what do sphincters do?
control the flow of urine
what is the conscious control of the bladder?
can be controlled consciously and unconsciously
what are cysometrogram?
measure bladder behaviour as it is stretched and compliance
what is the detrusor?
smooth muscle of bladder wall
what is the distinctive feature of the bladder wall?
allows large volume changes
how is the detrusor controlled?
autonomic reflexes
passive stretching of the wall triggers contractions
how is a cystometrogram done?
-multi barrel thin tube catheter
-allows fluid to fill bladder at a controlled rate
-allows pressure to be measured at several sites simultaneously: bladder, sphincter
what happens to pressure within the bladder when it fills?
urethra pressures > vesicle pressures = no flow out
when will bladder empty?
vesicle pressure > sphincter pressure or urethra pressure = fluid pushes past the sphincter
what are the stages of the storage phase?
- early filling phase
- no flow in urethra
- sensations develop
what happens during the early filling phase?
low pressure in bladder
bladder wall and external sphincter relaxed. no bladder sensation
what happens in the second stage?
no flow in urethra
urethral pressure > bladder pressure
what happens in the third phase?
sensations develop, sphincter contracts to maintain continence
what are the stages of the voiding phase?
- urge then voluntary voiding
- bladder contracts, urethra and sphincter relax. bladder pressure > urethral pressure
- voluntary stop flow then a 2nd voiding phase
what is the complex coordination?
external sphincter is skeletal muscle which changes force faster. urethra is smooth muscle which changes force slower. smooth muscle in bladder wall contracts. smooth muscle of urethra relaxes.
what is the innervation of the bladder and sphincters like?
sympathetic : from L1, L2 (bladder wall and internal sphincter)
parasympathetic : S2, S3 and S4 (bladder wall)
what is the afferent pathway ?
-sensory fibres sense the stretch of the bladder wall. these afferents run in the hypogastric nerve and enter coed in the upper lumbar roots
-other sensors near the urethra sense flow of urine
-skeletal muscle sensors in the external sphincter
what is the efferent point?
parasympathetic to detrusor
sympathetic to internal sphincter
somatic to external sphincter
storage phase?
sympathetic effects dominate during bladder filling
fibres in the hypogastric nerve suppress contraction of the detrusor
somatic fibres in the pudendal nerve control the external sphincter
voiding phase?
parasympathetic actions dominante during emptying
fibres in the pelvic sphlanic nerve cause the detrusor to contract.
reflex control?
via centres in the sacral cord in the pons
pontine centre coordinates with higher centres
which nerve fibres feel the sensations in the bladder?
-larger myelinated fibres
-small unmyelinated fibres
-small fibres are probably linked to unpleasant sensations
what is the basal cystometrogram?
everything relaxed, no contractions in bladder wall
what is. neurogenic bladder?
contractions start at a lower volume
what is an atonic bladder?
pressure rises slowly as bladder fills
what is the plumbing problem?
when urethra passes through prostate gland
-likely due to hypertrophy of the prostate with age
-can compress the urethra and slow the flow of urine
-can open up potential for toilet
-can prevent full emptying of bladder
