Bladder

Question 1

22 year old woman had a protracted breech delivery six weeks ago and has still not regained urinary continence. Which statement about neuronal control of micturition is correct?

Answer 1

external vesical sphincter is supplied by the pudendal nerve

Question 2

The micturition cycle has two distinct phases, storage and voiding. What is the primary event in the switch from storage to voiding?

Answer 2

Relaxation of the urethral sphincter

Question 3

What control is the detrusor muscle under

Answer 3

control of the autonomic system with some voluntary control

Question 4

A 28-year-old man requires a urethral catheter to be inserted prior to undergoing a splenectomy. Where is the first site of resistance to be encountered on inserting the catheter?

Answer 4

membranous urethra is the least distensible portion of the urethra. This is due to the fact that it is surrounded by the external sphincter.

Question 5

Urinary tract function

Answer 5

To collect the continuously produced urine
Store it under safe conditions
Void it when socially appropriate

Question 6

Goals of bladder management

Answer 6

Protect the kidneys
Reduce complications
Manage continence
Promote independence
Body a]image and sexuality
Self esteem and confidence

Question 7

Vermiculation

Answer 7

Active peristalsis
Kidneys protected against moderately raised bladder pressures

Question 8

Prevention of reflux

Answer 8

Competent ureter-vesical valves

Question 9

Urethral sphincters

Answer 9

Bladder neck
Distal urethral sphincter

Question 10

Bladder neck

Answer 10

Active during ejaculation only

Question 11

Distal urethral sphincter

Answer 11

Smooth muscle component
Intrinsic striated sphincter - rhabdosphincter
Extrinsic striated spinchter - pelvic floor

Question 12

Rhabdosphincter

Answer 12

Intrinsic striated distal urethral sphincter
Slow twitch striated muscle

Onuf’s nucleus - S2/3/4 anterior horn
Local afferent- guarding reflex

Question 13

Onuf upper motor neuron

Answer 13

Motor cortex
Corticospinal tract

Question 14

Bladder

Answer 14

Composed of multiple segments of smooth muscle with their associated ganglia
Each segment exhibits spontaneous activity - micromotions
Cannot be denervated
Has tone and activity as intrinsic characteristics

Question 15

Sacral micturition centre

Answer 15

Parasympathetic S2/3/4
- intermediolateral gray. Motor to bladder . Coordination of micromotions

C fibre local afferents
- reflex bladder contractions

Question 16

Sympathetic bladder control

Answer 16

Bladder- receptive relaxation
Bladder neck- ejaculaton
Sphincter- smooth muscle, non-relaxing sphincter obstruction

Question 17

Pontine micturition centre

Answer 17

Possible medial (micturition) and lateral (storage ) centres
Motor centre for the autonomic control of the lower urinary tract
Descending fibres presumed to be in anterio-lateral funiculus

Question 18

Periaqueductal gray

Answer 18

Visceral and somatic control centre for lower urinary tract
Receives A-delta fibre input
Communicated with conscious centres

Question 19

Cortex

Answer 19

Sensation
Voluntary initiation

Question 20

Midbrain

Answer 20

PAG/PMC
Co-ordination
Completion of voiding

Question 21

Spinal reflexes

Answer 21

Reflex bladder contraction- sacral micturition centre
Guarding reflex- onuf’s nucleus
Receptive relaxation sympathetic

Question 22

What are bladder and sphincter function coordinated by

Answer 22

Pontine micturition centre
Periaqueductal gray

Question 23

Receptive relaxation

Answer 23

A spinal reflex that suppresses intrinsic bladder activity to create compliance

Question 24

What are reflex bladder contractions due to

Answer 24

Co-ordination of micromotions by the sacral micturition centre

Question 25

What controls the voiding phase of micturition

Answer 25

Pontine micturition centre

Question 26

Which nerve stimulates voiding

Answer 26

Pelvic nerve

Question 27

Pelvic nerve roots

Answer 27

S2-S4

Question 28

Inhibition of onuf’s nucleus

Answer 28

pontine micturition centre also inhibits Onuf’s nucleus, with a resultant reduction in sympathetic stimulation to the internal urethral sphincter causing relaxation

Question 29

Voiding phase of micturition

Answer 29

Upon the voluntary decision to urinate, neurons of the pontine micturition centre fire to excite the sacral preganglionic neurons.

There is subsequent parasympathetic stimulation to the pelvic nerve (nerve roots S2-4) causing a release of acetylcholine (ACh), which works on muscarinic ACh receptors (M3 receptors) on the detrusor muscle, causing it to contract and increase intra-vesicular pressure. The pontine micturition centre also inhibits Onuf’s nucleus, with a resultant reduction in sympathetic stimulation to the internal urethral sphincter causing relaxation.

Finally, a conscious reduction in voluntary contraction of the external urethral sphincter from the cerebral cortex allows for distention of the urethra and the passing of urine.

Question 30

Urinary flow rate in men

Answer 30

20-25 ml/s

Question 31

Urinary flow rate in women

Answer 31

25-30 ml/s

Question 32

Which part of the brainstem is responsible for co-ordinating actions of the urinary sphincters and bladder

Answer 32

Pons

Question 33

Which nerve is responsible for sympathetic bladder control

Answer 33

Hypogastic nerve

Question 34

Hypogastric nerve roots

Answer 34

T10-L2

Question 35

Function of hypogastric nerve

Answer 35

Relaxation of the detrusor muscle in the bladder wall – via stimulation of β3-adrenoreceptors in the fundus and the body of the bladder.
Contraction of the IUS – via stimulation of α1-adrenoreceptors at the neck of the bladder

Question 36

Which nerve is responsible for somatic innervation of the bladder

Answer 36

Pudendal nerve

Question 37

Pudendal nerve roots

Answer 37

S2-S4

Question 38

Function of pudendal nerve during storage

Answer 38

impulses travel to the EUS via the pudendal nerve (nerve roots S2-S4) to nicotinic (cholinergic) receptors on the striated muscle, resulting in contraction of the EUS. This prevents any urine from leaking out.

Question 39

Co-ordinated effect for storage

Answer 39

The co-ordinated relaxation of the detrusor muscle and contraction of the urethral sphincters allows the bladder to fill and store urine for many hours. As the bladder fills, the folds in the bladder walls (rugae) flatten and the walls distend, increasing the capacity of the bladder. This means that, as the bladder fills, it expands, allowing the inner (intra-vesical) pressure to remain the constant and lower than urethral pressure. This process, known as receptive relaxation, is vital to the storage of urine and prevents leakage during this phase.

Question 40

Types of urinary incontinence

Answer 40

Stress
Urge
Overflow
Neurological

Question 41

Onuf’s nucleus

Answer 41

Through the pudendal nerve, Onuf’s nucleus innervates the external anal and urethral sphincters, as well as two perineal muscles: ischiocavernosus and bulbospongiosus. Hence, it maintains bowel and bladder continence through the voluntary control of both external sphincters and enables sexual functions like penile erection and ejaculation through perineal muscle contractions.

In addition to its motor functions, Onuf’s nucleus also performs autonomic functions by association with parasympathetic neurons in the sacral segment of the spinal cord.