function of bladder

Question 1

rates of bladder filling

Answer 1

Minimum urine production rate: ~ 1 ml/min (max ADH/AVP secretion)

Maximum urine production rate: ~ 20 ml/min (min ADH/AVP secretion)

Question 2

bladder behaviour and sensation

Answer 2

Bladder behaviour and sensations depends on volume and filling rate.

Stretch receptors in the bladder wall signal volume etc.
Sphincter activity maintains continence. Sub-conscious and conscious control.

Question 3

cystometrogram

Answer 3

• measures bladder behaviour and compliance

Question 4

bladder structure in males

Answer 4

Bladder wall: smooth muscle, (detrusor).
Smooth muscle allows large volume changes.
The activity of the detrusor muscle is affected by reflexes. Passive stretch of the wall triggers contractions.
Contraction of detrusor muscle produces additional force/pressure.

Question 5

techniques for investigation of bladder

Answer 5

Multi-barrel catheter.
Allows fluid to fill the bladder at a controlled rate.
Allows pressure to be measured at several sites simultaneously: bladder, sphincter etc
Some devices allow recording of sphincter muscle activity.

Question 6

technique for investigation instructions

Answer 6

Place one opening in the bladder to allow direct filling and measure bladder pressure.

Inflate balloon to close off urethra

Position second opening in the urethra to measure the sphincter pressure

Then fill the bladder and record the pressure to establish bladder compliance.

As bladder fills watch for signs of bladder wall contraction and sphincter contraction

Question 7

sphincter in males

Answer 7

• strong external sphincter
• skeletal muscle

Question 8

bladder structure in females

Answer 8

Less skeletal muscle.
Weaker external sphincter.

Question 9

storage phase

Answer 9

(Catheter as before, rapid filling rate, 20 ml/s!, calculate volumes.)
1. Early filling phase, low pressure in bladder, bladder wall and ext sphincter relaxed.

2. No flow in urethra: urethral pressure > bladder pressure.
3. Sensations develop , then sphincter contracts to maintain continence.

Question 10

voiding phase

Answer 10

‘Urge’ then ‘Voluntary voiding’.
Bladder contracts, urethra and sphincter relaxes . in Flow in urethra: bladder pressure > urethral pressure.
‘Voluntary’ stop flow then a 2nd voiding phase ,

Question 11

complex coordination of urination

Answer 11

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 in urethra relaxes

Question 12

innervation of bladder and sphincters

Answer 12

Sympathetic: from L1, L2
Bladder wall and internal sphincter
Parasympathetic: from S2, S3 and S4
Bladder wall
Somatic: from S2, S3 and S4. Sensory and motor to external sphincter

Question 13

afferent bladder control pathway

Answer 13

1. Sensory fibres sense the stretch of the bladder wall. These afferents run in the hypogastric nerve and enter cord in the upper lumbar roots.
2. Other sensors near the urethra sense flow of urine.
3. Skeletal muscle sensors in the external sphincter.

Question 14

efferent control pathway

Answer 14

1. Parasympathetic to detrusor
2. Sympathetic to internal sphincter
3. Somatic to external sphincter

Question 15

storage phase, bladder control

Answer 15

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

Question 16

riding phase, bladder control

Answer 16

Parasympathetic actions dominate during emptying. Fibres in the pelvic splanchnic nerve cause the detrusor to contract.

Question 17

reflecting control, bladder control

Answer 17

via centres in the sacral cord and in the pons.Pontine centre coordinates with higher centres.

Question 18

sensations which accompany filling

Answer 18

No sensation then a ‘sense of filling’
Then ‘fullness’, then ‘desire’
Then ‘discomfort’ and ‘pain’.

Sensations depend on rate of filling

Sensations are supported by larger myelinated fibres and small unmyelinated fibres.
Small fibres probably linked to unpleasant sensations

Question 19

plumbing problems in males

Answer 19

The urethra passes through the prostate gland.
With age, there is likely to be hypertrophy of the prostate (benign or otherwise?)
This can compress the urethra and slow the flow of urine.
This can prevent full emptying and lead to more frequent voiding.

Question 20

flow rates

Answer 20

If urethra is narrowed, flow rate is reduced.
Time of flow is increased.
Volume voided may be reduced, leading to increased frequency of voiding.