Micturition reflex Flashcards
What transports urine from calices to the bladder?
The ureters
How does urine flow through the calices?
The calices stretch from increased volume, this stimulates pacemaker activity therefore initiating peristalsis
What system increases pacemaker activity in the kidney?
It is increased by the parasympathetic nervous system
What is the function of the inner layer/ transitional epithelium of the kidney?
Contains rugae that help it stretch, therefore reducing back pressure on the kidney
What is the reason behind the ureter having an oblique path as it enters the bladder?
It creates a ‘valve-like’ entry, reducing urinary reflux and damage
Through which muscle do ureters enter the bladder?
Through the detrusor muscle
What is the name of the cells that line the transitional urothelium that lines the renal calices, bladder etc.
Fully differentiated umbrella cells
How are umbrella cells bound to eachother?
with tight junctions and they form a waterproof barrier
How does the uretorenal reflex work?
When there is a blockage in one of the ureters, the ureter constricts, this causes the pain fibres to also constrict
The pain impulses then cause the renal arterioles to constrict which reduces fluid flow through the blocked ureter
What does contraction of the detrusor muscle do?
keeps the ureter compressed
What is vesicoureteral reflux?
When the vesicoureteral junction does not work, urine flows backwards from the bladder up to the kidney
What parts of the bladder are under involuntary control?
the detrusor and internal sphincter
What parts of the bladder are under voluntary control?
The external sphincter
What is the firing rate of the stretch sensitive fibres in the lining of the bladder when the bladder is empty?
Relatively slow
What occurs when slow impulses from the bladder occur?
Sympathetic system is stimulated, this means that the internal sphincter contracts and the detrusor muscle relaxes in order to allow urine to be stored
Signals are sent to be micturition part of the brain to tell the body that ‘you do not need to wee’
What occurs when fast impulses from the bladder occur?
The parasympathetic system is stimulated, the detrusor muscle contracts and the internal sphincter relaxes, allowing for urination
Signals are also sent to the pons telling it that ‘you need to wee’
If it is unsafe to urinate signals are sent to the somatic nervous system, (pudendal nerve) and the external sphincter contracts
What causes uncontrolled urination?
A cerebral lesion
What is the result of trauma to the lumbar spine or more cranial than the lumbar spine?
Hypogastric nerve component is lost (damage to sympathetic nervous system) so everything goes into contraction/ spasm (detrusor and internal sphincter both contract)
The bladder is full, turgid and difficult to express
This is also called UMN bladder
What is the result of trauma to the sacral region of the spine?
Reduced or lost muscle tone, large flaccid (relaxed) bladder that is easy to express (damage to both somatic and parasympathetic NS) , the patient may dribble urine
This is also known as LMN bladder
What is the result of any damage to the caudal end of the spine?
Should have no effect on the bladder
Describe the uretorenal reflex?
Pain fibres in the ureters cause vasoconstriction of arterioles when the ureters become blocked, this prevents excess fluid from entering the kidney
Describe the Vesicoureteric reflex
When the detrusor muscle contracts the ureters should be pressed against the bladder wall, preventing any urine from re-entering them
However if there is damage, sometimes this failsafe does not work (vesicoureteric reflux)
