Control Of Micturition Flashcards
What are the layers of the bladder
Urothelium
Lamina propria
Detrusor muscle
Serosa
Features of the urothelium
Tight junctions of prevent any movement of fluid or substances between the urine and the interstitium
Umbrella cells which protect the underlying epithelium covering them also act to stretch when the bladder fills
Underlying epithelial is transitional epithelium so as the bladder fills it changes shape from more rounded cells to a flatter shape
Detect chemical constituents of the urine
Features of the lamina propria
Contains BV, nerves and lymphatics
Chemical constituents detected in the urine lamina propria conveys the signals to the detrusor muscle - contract or relax
Interstatial cells of cajal
These are through to act to transmit the chemical detection signals to the detrusor with no nerves
Features of the detrusor muscle
Basket weave of smooth muscles cells
Innervated with sympathetic and parasympathetic fibres
Sympathetic relax - continence
Parasympathetic contract in voiding
What are the receptors for the sympathetic input and the NT
B3 noradrenaline
Relaxation of the muscle
What are the receptors for the parasympathetic input and the NT
M3
Ach
Contraction
Feature of the serosa
Acts to maintain the integrity of the bladder when full
Where do sensory input go to in the brain about the state of filing of the bladder
Pontine micturition centre
Internal urethral sphincter - muscle
Smooth muscle
Circular fibres
External urethral sphincter muscle
Skeletal muscles
Longitudinal
Which nerve supplies the EUS
Pudendal nerve
IUS nerve supply
Sympathetic alpha receptors of NA to contract it
What is the storage reflex - higher centre involvement
Inc in pressure detected
Pontine micturition centre fibres descend and synapse with the skeletal muscle causing contraction
What is the storage reflex- local
Increasing pressure stretched bladder wall
Local reflex from pelvic afferents to the pudendal nerve which contracts the EUS
Also sympathetic reflex causing relaxation of the detrusor
What happens in voiding
Inactivation of sympathetic and somatic
Activation of parasympathetic
Results in relaxation of EUS
Contraction of detrusor
When is urinary continence affected
UTI chemical stimuli increase the eed for micturition
Spinal cord transection different levels cause different problem - continence and voiding
Strokes
Pelvic floor injury - following childbirth damage to the anterior vaginal wall
Detrusor over activity- outflow obstructions -smooth muscle hypertrophy -bladder contraction too forceful to control
Atonic Bladder syndrome -bladder fills until pressure high, slow leak of urine
How is overactive bladder managed pharmacologically
Anti muscarinic drugs - oxybutynin useful but show tolerance
Botulinum toxin injections into bladder prevent Ach release and stop contraction - ongoing and repeated process
Target sensory nerves prevent reflex generation resiniferatoxin
B3 agonists mirabegron
Type 5 PDE inhibitors - sildenafil
K+ channel activators
What most commonly causes urinary outflow obstruction
Benign prostatic hyperplasia
Treat BPH
Surgically - transurethral resection of the prostate
Medication-
Alpha adrenoceptor antagonists relax smooth muscle in prostate - tamsulosin
5 alpha reductase inhibitors finesteride reduce hypertrophy
