Micturition

Question 1

is micturition under autonomic or voluntary control

Answer 1

both

Question 2

2 modes of bladder operation

Answer 2

storage and elimination

Question 3

shape of the bladder

Answer 3

triangular pyramid shape
4 surfaces = superior, base (posterior), 2 inferior lateral
ureter and urethral openings

Question 4

4 uncles control micturition

Answer 4

• detrusor muscle (wall of bladder)
• internal urethral sphincter (valve controls output of urine - autonomic NS)
• external urethral sphincter (lower voluntary control)
• bulbospogiosus muscle (penis)

Question 5

full bladder capacity

Answer 5

500 ml
Pelvic organ

Question 6

bladder dullness felt at

Answer 6

400 ml

Question 7

is passing urine sympathetic or parasympathetic

Answer 7

passing out urine = parasympathetic

Question 8

holding in urine sympathetic or parasympathetic

Answer 8

sympathetic

Question 9

nerves controlling micturition

Answer 9

1. sympathetic nerves
   2a parasympathetic efferent nerves
   2b sensory stretch nerves (parasympathetic afferent)
   3 somatic nerves

Question 10

nerves controlling micturition

Answer 10

1. sympathetic nerves
   2a parasympathetic efferent nerves
   2b sensory stretch nerves (parasympathetic afferent)
   3 somatic nerves

Question 11

sympathetic nerves

Answer 11

T12-L2
contain urine
contract - internal urianry sphincter
Relax - detrusor muscle (wall)

Question 12

Parasympathetic nerves

Answer 12

S2-S4
release urine
Contract - detrusor muscle (wall)
Relax - internal urianry sphincter (open up)

Question 13

somatic nerves

Answer 13

control external urethral sphincter
voluntary control
tighten if holding in urine

Question 14

Pontine micturition centre

Answer 14

Pons in the brainstem
micturition junior manager
relay station for ascending spinal bladder information and higher brain areas

Question 15

what happens when bladder is full but can’t go to the toilet

Answer 15

• neurons are silent when bladder empty
• activated when stretch mechanoreceptors are triggered when full
• relaxes external urethral sphincter
• contracts detrusor muscles
• bathroom is full = brain inhibits Pontine micturition centre(PMC) !!

Question 16

what is the cerebral aqueduct

Answer 16

surrounded by periaqueductal grey (PAG)
important sensory anf motor relay station

Question 17

various clinical situations where nerves control micturition

Answer 17

• foetal urination
• renal genesis
• automatic reflex bladder - babies
• spontaneous urination nappy change
• potty training
• bed wetting
• emptying urines from male urethra
• urination difficulty during erection
• ejaculation
• autonomous bladder (loss of parasympathetic)
• atonic bladder
• automatic reflex bladder after spinal shock
• micturition in patients with dementia

Question 18

foetal urination

Answer 18

• foetus suspended in amnion fluid
• amnion fluid largely created by urine
• small extent by the lungs
• urine in the amnion fluid gets more concentrated as gestation approaches
• drinking urine and faeces

Question 19

what happens if there is insufficient urine in amnion fluid

Answer 19

• under developed lungs - fatal
• causes contractures and club feet
• renal agenesis - baby has no kidneys and not surrounded by enough amnotic fluid -malformed lungs

Question 20

Pseudoglandular phase

Answer 20

7th to 17th week
by 8th week 17 orders of branching
formation of bronchial tree up to terminal bronchioles

Question 21

what produced amniotic fluid

Answer 21

Broncho pulmonary epithelium

Question 22

involuntary micturition reflex

Answer 22

1. stretch receptors detect filing of bladder - transmit afferent signals to spinal cord
2. signals return to bladder from SC segments S2 and S3 via parasympathetic fibres in pelvic nerve
3. efferent signals excite detrusor muscles
4. efferent signals relax internal urethral sphincter - urine is involuntary folded if not inhibited by brain

Question 23

micturition reflex voiding - nappy change what can urination be triggered by

Answer 23

• suprapubic percussions
• thigh scratching
• touching penile skin
• pulling pubic hair

Question 24

nerves of micturition reflex

Answer 24

• sends afferent signals through the pudendal nerve to S2-4 spinal cord levels
• efferent through the pelvic parasympathetic nerves S2-S4 to relax the internal urethral sphincter and contract the detrusor muscles
• other rats lick the urine odour on baby rats and triggers micturition
• isolated baby rats die due to lack of urination

Question 25

Voluntary control of micturition

Answer 25

* micturition centre in ponse recibes signals form stretch receptors * is time to urinare - pons returns signals to spinal interneurons that excite detrusor and relax internal urethral sphincter urine is voided * is it is NOT time to urinate = signals from cerebrum excite spinal interneurons that keep external uretheral sphincter contracted - urine is retained in bladder = then if urinate = signals from cerebrum inhibit sacral neurons that keep external sphincter close - external urethreal sphincter relies - urine released

Question 26

why do children wet the bed

Answer 26

* ascending stretch sensory information form bladder wall to the brain does not wake up the child * brain does not inhibit the external urethral sphincter * automatic reflex bladder in babies sets in * to prevent renal damage

Question 27

emptying urine from ale urethra

Answer 27

* Use bulbospongious muscle to empty the final 5% of wine from the bladder * supplied by the somatic pudendal nerve

Question 28

why can't you urinate during an erection

Answer 28

* parasympathetic nerves - allow urination to proceed * parasympathetic nerves - allow erection * pressure in the corpus spongiosum compresses the urethra * during ejaculation = pressure in urethra is enough to over power the corpus spongiosum and generate a fountain

Question 29

ejacuation para or sympathetic

Answer 29

ejaculation = sympathetic activity

Question 30

ejaculation

Answer 30

sympathetic nerves relax detrusor muscle contract internal urethral sphincter pudendal nerve contracts the bulbocavernosus muscle = stops semen escaping into the bladder and allows it to escape

Question 31

Autonomous bladder

Answer 31

* due to loss of sacral nerves * parasympathetic and pudendal nerves lost * cause relaxation of detrusor and onctraction of internal urethral sphincter * urination is abolished * backfill = renal failure * catheterisation = relief

Question 32

Atonic bladder

Answer 32

* neurogenic bladder * occurs when spinal cord is damaged and spinal shock * few to several days * detrusor muscles relax * internal urethral sphincter contracts * urine retained and patient may not be aware

Question 33

Automatic reflex bladder in adults

Answer 33

* after atonic bladder stage ( similar to in babies ) every 1- 4 hours

Question 34

involuntary micturition reflex

Answer 34

1. stretch receptors detect filling og bladder transmit afferent signals to SC 2. signals return to bladder from SC segments S2 and S3 via parasympathetic fibres in pelvic nerve 3. efferent signals excite detrusor muscle 4. efferent signals relax internal urethral sphincter urine is involuntary voided if not inhibited by brain

Question 35

dementia - micturition

Answer 35

* half of patients in nursing homes have bladder control problems * incontinence - very expensive - diapers, care, laundry * difficulty of the cerebrum in interpreting micturition sensory information * loss of visuospatial abilities - harder to find the toilet * might have locomotion problems = difficulty of holding urine until when they reach the toilet seat

Question 36

apraxia

Answer 36

difficulty of undressing and using toilet