Week 8 - Control of micturition Flashcards
What is the significance of the bilateral neural supply?
- Both sides need to be damaged to loose all control
- Parasymp and symp input mean it is difficult to treat
What epithelium lines the detrusor?
-transitional epithelium
Describe parasympathetic input to the detrusor
-Causes contraction of the detrusor through ach acting on m3 receptors via pelvic nerve
Describe sympathetic input to the detrusor
-Relaxation through NA acting on b3 receptor via hypogastric nerve
Describe the internal urethral sphincter
-Physiological sphincter which acts as a passive valve
What innervates the external urethral sphincter?
-Somatic innervation through pudendal nerve S2-S4
When is the micturition reflex initiated?
-In response to opening of EUS
What controls the storage phase of continence?
- Sympathetic neurones (continence neurones)
- Somatic nervous system
- Continence centres in the brain (pontine storage centre)
How much urine can the bladder store?
-Upto 1L
At what ml do we get the need for micturition?
-550ml
How does the pontine storage centre control continence?
-Output from the PSC causes relaxation of the detrusor muscle via sympathetic B3 innervation and increases EUS pressure through a-adrenoreceptors in the neck of the bladder
What are the root values of sympathetic NS which control continence?
-T10/12-L2
What controls micturition/voiding function?
- Parasympathetic neurones
- Micturition centres in the pons
How does the bladder signal to micturition centre in pons?
-Afferent nerves in trigone detect stretch, pain and temperature
How does the micturition centre cause micturition?
- Brain informs sacral parasympathertic outflow of spinal cord which stimulates contraction of detrusor via ach acting on m3 in bladder
- Increasing intravesicle pressure relaxes IUS
- Voluntary relaxation of EUS
