Control of Micturition Flashcards
Describe the structure of the Bladder wall ( Hint: 4 )
1- Mucosal layer : internal lining
2- submucosal layer : sensory
3- Detrusor layer ( contractile ) : smooth muscle that when stretched there is spontaneous contraction and need to urinate
4- serosa
Explain the two phases of the bladder
1- Bladder filling = increased wall tension
2- Bladder emptying - micturition reflex & contraction
Describe the anatomy of the bladder
Muscular sac that is flaccid when empty and turgid when full
How does the urine enter the bladder
urine enters bladder from ureters via the ureteric orifices
What stops the urine from leaving the bladder
2 sphincters blocking the urethra:
1 - involuntary smooth muscle sphincter - internal urethral sphincter
2- voluntary skeletal muscle sphincter - external urethral sphincter
What structures need to contract / relax for urination
Both sphincters must relax and detrusor muscle must contract
What are the interstitial cells of Cajal
Sensory cells that interact with smooth muscles in detrusor layer to control and initiate contraction
- Also convey sensory info to nerves
Where are ICCs found (Hint: 3 areas )
Bladder, small intestine , large intestine
What is the epithelium of the mucosal layer
Transitional epithelium
What does the submucosal layer of the bladder consist of
1- Lamina propria with ICCs
2- nerves
3- muscularis mucosa that moves epithelium to limit urine exposure
What does the detrusor layer of the bladder consist of
1- ICCs
2- smooth muscles
3- nerved
What tones does the detrusor layer control
1- Basal tone for spontaneous activity
2- Expulsion tone during micturition
Explain the afferent innervation of the bladder
3 bundles of sensory nerved relay info about filling bladder and sphincter pressure to spinal cord
1- Sympathetic pelvic : bladder stretch
2- Parasympathetic hypogastric : bladder stretch and internal sphincter pressure
3- Sensory somatic nerved : external sphincter pressure
Explain the efferent innervation of bladder detrusor
1- Sympathetic efferent fibres from lumbar spinal cord : inhibitory
2- parasympathetic efferent from sacral spinal cord : excitatory
Explain the innervation of the internal urethral sphincter
Innervated by sympathetic efferents from lumbar spinal cord
Release of what substance contracts the internal urethral sphincter
noradrenaline
Explain the innervation of the external urethral sphincter
Innervated by somatic efferent fibres in Pudenal nerves. Signals from brain constrict this sphincter at all times except when voiding
What substance stimulates the skeletal muscle contraction of the external urethral sphincter
ACH
Where do the somatic nerved innervating the bladder enter and emerge from
Spinal cord between S2&S4
Where do the pelvic nerves innervating the bladder enter and emerge from
Spinal cord between S2&S4
Where do the sympathetic nerves innervating the bladder enter and emerge
Spinal cord around T11-T12
What is the micturition reflex
Bladder contraction reflex when the bladder fills
Explain in detail the mechanism of the micturition reflex ( Hint: 4 steps )
1- Bladder fills and ICCs detect stretch
2- Parasympathetic afferent nerves synapse onto parasympathetic efferent nerves resulting in reflex arc
3- Detrusor muscle contraction is stimulated
4- voiding
How does the bladder relax after micturition reflex without voiding and what does this allow
1- Pressure on the internal sphincter will stimulate a sympathetic reflex that contracts the internal sphincter and relaxes the bladder.
2- parasympathetic efferent synapse on ascending nerves to pons which results in conscious control of micturition and activates somatic efferents to close external urethral sphincter
Allows bladder to fill
Explain in detail the mechanism of voiding (Hint: 5 steps )
1- Parasympathetic sensory nerved report to pons that bladder is almost full
2- parasympathetic motor nerves inhibition by pons is stopped = bladder can contract in response to stretch ( micturition reflex)
3- sympathetic motor nerves are inhibited by pons = internal sphincter relaxes
4- somatic motor signals are inhibited by pons = external sphincter relaxes
5- Voiding activated via micturition reflex causing detrusor contraction
What are the 4 phases of micturition
1- after micturition signals sent to contract sphincters and relax bladder , sensory and parasympathetic inactive
2- First sensation to void : stretch detected by ICCs is communicated by nerves , parasympathetic is inhibited, sphincters still contracted
3- Desire to void: sensory neurons very active and parasympathetic inhibited, sphincters contracted
4- Voiding : parasympathetic active leading to micturition , sensory active , sphincters relaxed
5- sensory signal bladder is empty so sphincters are contracted and micturition is inactivated
List the 4 types of incontinence ( disorders of micturition )
1- Stress incontinence
2- Urge incontinence
3- Overflow incontinence
4- Neurogenic incontinence
What is Atonic bladder
Overflow incontinence where a large dilated urinary bladder doesn’t empty
List the causes ( in detail ) of atonic bladder
1- Chronic obstruction : prostate cancer, urethra narrowing
2- innervation disturbance
3- sensory nerve damage during child birth
4- adverse effect of anticholinergic medications , calcium channel blockers , adrenergic agonists
5- Epidural anaesthesia
What is the treatment of Atonic bladder
1- Bethanechol ( m3 agonist ) to improve contraction force
2- catheterization
3- surgery : widen urethra, remove prostate
What is stress incontinence
Bladder leakage when sneezing and coughing due to weakening of pelvic floor muscles supporting the external urethral sphincter
List the causes of stress incontinence ( Hint: 5 )
1- Post-surgical complication of prostate
2- physical changes from pregnancy, child birth , menopause
3- obesity
4- caffeine
5- smoking
What is the treatment for stress incontinence (Hint:7)
1- pelvic muscle exercises
2- stop mid micturition flow to improve PFM strength
3- electric stimulation of muscles
4- loose weight
5- decrease fluid intake ( caffeine & carbonated )
6- stop alcohol , smoking
7- artificial sphincter surgery or sling to support PFM surgery
How does smoking result in stress incontinence
nicotine inhibits nicotinic receptors in external sphincter which would normally bind to ACH to constrict
What is OAB
Overactive bladder aka urge incontinence. High micturition frequency
Does OAB occur with loss of bladder control
can occur with or without loss of bladder control
List the causes of OAB (HINT: 7)
1- oversensitivity due to UTI 2- oversensitivity due to over stimulation of bladder detrusor 3- obesity 4- caffeine 5- constipation 6- poorly controlled diabetes 7- chronic pelvic pain
What is the treatment of OAB ( hint: 5 )
1- reduce bladder sensitivity by drinking more water
2- decrease caffeine and citrus
3- bladder training and behavioural methods
4- Botulinum toxin to reduce ACH release = reduce contraction
5- anti- muscarinic to reduce contraction
List the causes of neurogenic bladder dysfunction
1- Spinal cord injury
2- crush injury ( child birth )
3- stroke
3- CNS diseases
What is neurogenic bladder dysfunction ( Explain in detail what happens )
When the ascending and descending inputs are lost so there is no voluntary control of micturition. Detrusor becomes overactive since there are no inhibitory influences preventing filling. Internal sphincter may be operational depending on damage.
What is the treatment for neurogenic bladder dysfunction
1- Managed micturition with intermittent catheterization
2- botox capsaicin to reduce reflex voiding
3- muscarine receptor antagonist to improve filling by reducing ACH
What is Crede’s maneuver
manual pressure is exerted on abdomen below the navel
