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GERR > Lecture 41: Control of Micturition > Flashcards

Lecture 41: Control of Micturition Flashcards

1
Q

what is micturition

A

the process by which the urinary bladder is emptied when it becomes full

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2
Q

describe the 2 main phases of micturition

A

bladder filling:
- causes ^ wall tension (storage)

bladder emptying:
- (micturition reflex - bladder emptying

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3
Q

what people might experience involuntary micturition reflex

A
  • infants
  • elderly
  • those w/ neuro injury
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4
Q

what are the 4 layers of the bladder wall

A
  • mucosal layer
  • submucosal layer
  • detrusor layer
  • serosa
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5
Q

what are the 4 main types of incontinence

A
  • stress
  • urge
  • overflow (atonic bladder)
  • neurogenic
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6
Q

what is another name for overflow incontinence

A

atonic bladder

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7
Q

what is the cause of stress incontinence

A
  • weak pelvic floor muscles means external urethral sphincter doesn’t function effectively
  • external forces e.g. coughing, sneezing, exercise, cause urine to seep out
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8
Q

what is the treatment of stress incontinence

A
  • pelvic muscle exercises
  • bladder training –> stopping mid flow
  • electrical stimulation
  • lose weight
  • dec. fluid intake esp caffeinated/carbonated drinks, alcohol, citrus fruits
  • surgery –> artificial sphincter
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9
Q

causes of overflow incontinence

A
  • chronic obstruction (e.g. benign prostatic hyperplasia, prostate cancer, narrowing of urethra)
  • sensory nerve damage during child birth
  • adverse effect of some meds e.g. anticholinergics
  • epidural anaesthesia
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10
Q

what is the treatment of overflow incontinence

A
  • meds e.g. bethanechol (M3 agonist)
  • catheterisation
  • surgery e.g. removal of prostate
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11
Q

causes of urge incontinence

A
  • oversensitivity due to UTIs
  • over stimulation of bladder detrusor
  • risk factors:
  • -> obesity
  • -> caffeine
  • -> constipation
  • -> poorly controlled diabetes
  • -> poor functional mobility
  • -> chronic pelvic pain
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12
Q

treatment of urge incontinence

A
  • drink more water
  • dec caffeine and citrus fruit intake
  • bladder training
  • botulinum toxin –> reduces EACh release
  • antimuscarinic meds
  • NSAIDs
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13
Q

describe urge incontinence

A
  • overactive bladder
  • frequency and urgency night and day
  • w/ or w/o loss of bladder control
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14
Q

causes of neurogenic incontinence

A
  • spinal cord injury
  • crush injury e.g. child birth (can recover after reduction of inflammation)
  • severance –> asc. and desc. inputs lost
  • disease of CNS e.g. stroke, MS, Parkinson’s…
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15
Q

treatment of neurogenic incontinence

A
  • managed micturition w/ intermittent catheterisation
  • crede’s manœuvre
  • -> exerting manual pressure on abdomen just below navel
  • -> not recommended for long term
  • improve filling w/ chemicals to reduce overactive reflex voiding:
  • -> muscarinic rec antag
  • -> botox to reduce ACh release in detrusor
  • -> desensitisation of ICCs and sensory inputs to spinal cord w/ capsaicin (TRPV1 desensitiser)
  • -> electrical stimulation (transcutaneous tibial nerve stim)
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16
Q

what can neurogenic incontinence result in

A
  • no control of external urethral sphincter
  • no voluntary control of micturition reflex
  • ## detrusor may become overactive due to no inhibitory influences
17
Q

what can neurogenic incontinence result in

A
  • no control of external urethral sphincter
  • no voluntary control of micturition reflex
  • detrusor may become overactive due to no inhibitory influences
18
Q

what does emptying of the bladder rely on

A

bladder contraction which results from autonomic spinal reflex

19
Q

describe the mucosal layer of the bladder wall

A
  • interface

- transitional epi designed to stretch

20
Q

describe the submucosal layer of the bladder wall

A
  • sensory
  • lamina propria contains ICCs and nerves
  • Muscularis mucosae may move epi to limit exposure to urine
  • paracrine influences on underlying detrusor layer
21
Q

describe the detrusor layer of the bladder wall

A
  • contractile
  • contains ICCs, smooth muscle and nerves
  • stretch evoked spontaneous activity is inherent - basal tone
  • expulsion tone (cholinergic) during micturition
22
Q

what is immunohistochemistry

A

labelling of proteins w/ fluorescently tagged antibodies

23
Q

what are the cKit +ve sensory cells found in the detrusor layer of bladder wall

A

interstitial cells of Cajal (ICCs)

24
Q

what is the role of ICCs

A
  • interact w/ smooth muscle cells to control and initiate contraction
  • interact w/ nerves in detrusor layers conveying sensory info to nerves and contractile info back to smooth muscle cells
25
Q

where else in the body are ICCs found and what is their role there

A
  • small and large intestine

- thought to generate peristalsis

26
Q

what are the 3 nerve groups that innervate the bladder

A
  • somatic
  • sympathetic (hypogastric)
  • parasympathetic (pelvic)
27
Q

describe the afferent innervation of the bladder

A
  • sensory nerves (in all 3 nerve groups)
  • parasympathetic (pelvic)
  • -> report about bladder stretch
  • sympathetic (hypogastric)
  • -> report about bladder stretch and internal sphincter pressure
  • somatic (pudendal)
  • -> report about external sphincter pressure to pons
28
Q

outline what nerves innervate the detrusor muscle of bladder

A

sympathetic (hypogastric) and parasympathetic (pelvic) efferent

29
Q

what is the main contractile tissue of the bladder wall

A

detrusor muscle

30
Q

outline the difference in parasympathetic and sympathetic efferent innervation of the detrusor muscle

A

sympathetic = inhibitory

parasympathetic = excitatory

31
Q

describe the innervation of the bladder sphincters

A
  • internal urethral sphincter
  • -> sympathetic (hypogastric) efferent
  • -> release of noradrenaline contracts smooth muscle
  • external urethral sphincter
  • -> somatic (pudendal) efferent
  • -> release of ACh stimulates skeletal muscle contraction (voluntary control)
32
Q

where in the spinal cord do each of the groups of nerves that innervate the bladder enter and emerge from

A

somatic:
- S2 + S4

parasympathetic:
- S2-S4

sympathetic:
- T11-L2 (L1-L3)

33
Q

describe micturition reflex

A
  • bladder fills –> ICCs detect stretch –> message passed to adjacent nerves
  • parasympathetic afferents synapse onto parasympathetic efferents in spinal cord
  • bladder strecth w/ filling stimulates bladder contraction
  • = micturition reflex = voiding
34
Q

what prevents immediate voiding in micturition reflex and allows bladder to fill

A
  • pressure on internal sphincters stimulates sympathetic reflex
  • internal sphincters constrict and bladder relaxes allowing bladder to fill
35
Q

describe the process by which conscious control can override micturition reflex and allow bladder to fill

A
  • bladder stretch also signalled to PONS
  • parasympathetic afferents also synapse onto asc. nerves to PONS and higher centres of brain
  • PONS talks to higher centres, higher centres talk back to PONS
  • conscious control of micturition
  • pons overrides parasympathetic efferents and activates somatic efferents
  • relaxes bladder and constricts external urethral sphincter
  • allows for inhibition of micturition reflex, urination at convenient time, and bladder to fill
36
Q

outline the process that leads to bladder contraction once the bladder is full

A
  • parasympathetic afferents report that bladder is nearly full to PONS and higher centres
  • inhibition of parasympathetic efferents by PONS is relieved
  • micturition reflex occurs
  • bladder detrusor contracts
37
Q

describe the effect of bladder detrusor contraction on the sphincters and the process that allows voiding of the bladder to occur

A
  • when bladder detrusor contracts, puts more pressure on sphincters (urge to go)
  • both sphincters need to relax for voiding to occur
  • sympathetic efferents inhibited by PONS –> internal urethral sphincters relax
  • PONS switches off somatic efferent signals and external urethral sphincters relax
  • detrusor contraction forces urine out of bladder
  • = voiding
38
Q

describe the 4 phases of micturition in summary

A

start - initial bladder filling:

  • sensory nerves inactive
  • micturition reflex inactive
  • sphincters contracted

first sensation to void:

  • sensory nerves active
  • micturition reflex active but inhibited by PONS and higher centres
  • sphincters contracted (PONS + HC)

normal desire to void:

  • sensory nerves highly active
  • micturition reflex inhibited
  • sphincters contracted as urine pushed against them

micturition:
- PONS + HC override inhibition of micturition reflex
- brain switches off somatic signal –> sphincters relax
- bladder detrusor contraction
- voiding occurs
- sensory nerves signal bladder is empty and cycle begins again

39
Q

describe overflow incontinence

A

large dilated urinary bladder that does not empty

GERR (46 decks)

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