Micturition reflex

Question 1

What transports urine from calices to the bladder?

Answer 1

The ureters

Question 2

How does urine flow through the calices?

Answer 2

The calices stretch from increased volume, this stimulates pacemaker activity therefore initiating peristalsis

Question 3

What system increases pacemaker activity in the kidney?

Answer 3

It is increased by the parasympathetic nervous system

Question 4

What is the function of the inner layer/ transitional epithelium of the kidney?

Answer 4

Contains rugae that help it stretch, therefore reducing back pressure on the kidney

Question 5

What is the reason behind the ureter having an oblique path as it enters the bladder?

Answer 5

It creates a ‘valve-like’ entry, reducing urinary reflux and damage

Question 6

Through which muscle do ureters enter the bladder?

Answer 6

Through the detrusor muscle

Question 7

What is the name of the cells that line the transitional urothelium that lines the renal calices, bladder etc.

Answer 7

Fully differentiated umbrella cells

Question 8

How are umbrella cells bound to eachother?

Answer 8

with tight junctions and they form a waterproof barrier

Question 9

How does the uretorenal reflex work?

Answer 9

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

Question 10

What does contraction of the detrusor muscle do?

Answer 10

keeps the ureter compressed

Question 11

What is vesicoureteral reflux?

Answer 11

When the vesicoureteral junction does not work, urine flows backwards from the bladder up to the kidney

Question 12

What parts of the bladder are under involuntary control?

Answer 12

the detrusor and internal sphincter

Question 13

What parts of the bladder are under voluntary control?

Answer 13

The external sphincter

Question 14

What is the firing rate of the stretch sensitive fibres in the lining of the bladder when the bladder is empty?

Answer 14

Relatively slow

Question 15

What occurs when slow impulses from the bladder occur?

Answer 15

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’

Question 16

What occurs when fast impulses from the bladder occur?

Answer 16

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

Question 17

What causes uncontrolled urination?

Answer 17

A cerebral lesion

Question 18

What is the result of trauma to the lumbar spine or more cranial than the lumbar spine?

Answer 18

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

Question 19

What is the result of trauma to the sacral region of the spine?

Answer 19

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

Question 20

What is the result of any damage to the caudal end of the spine?

Answer 20

Should have no effect on the bladder

Question 21

Describe the uretorenal reflex?

Answer 21

Pain fibres in the ureters cause vasoconstriction of arterioles when the ureters become blocked, this prevents excess fluid from entering the kidney

Question 22

Describe the Vesicoureteric reflex

Answer 22

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)