Micturition Flashcards
is micturition under autonomic or voluntary control
both
2 modes of bladder operation
storage and elimination
shape of the bladder
triangular pyramid shape
4 surfaces = superior, base (posterior), 2 inferior lateral
ureter and urethral openings
4 uncles control micturition
- detrusor muscle (wall of bladder)
- internal urethral sphincter (valve controls output of urine - autonomic NS)
- external urethral sphincter (lower voluntary control)
- bulbospogiosus muscle (penis)
full bladder capacity
500 ml
Pelvic organ
bladder dullness felt at
400 ml
is passing urine sympathetic or parasympathetic
passing out urine = parasympathetic
holding in urine sympathetic or parasympathetic
sympathetic
nerves controlling micturition
- sympathetic nerves
2a parasympathetic efferent nerves
2b sensory stretch nerves (parasympathetic afferent)
3 somatic nerves
nerves controlling micturition
- sympathetic nerves
2a parasympathetic efferent nerves
2b sensory stretch nerves (parasympathetic afferent)
3 somatic nerves
sympathetic nerves
T12-L2
contain urine
contract - internal urianry sphincter
Relax - detrusor muscle (wall)
Parasympathetic nerves
S2-S4
release urine
Contract - detrusor muscle (wall)
Relax - internal urianry sphincter (open up)
somatic nerves
control external urethral sphincter
voluntary control
tighten if holding in urine
Pontine micturition centre
Pons in the brainstem
micturition junior manager
relay station for ascending spinal bladder information and higher brain areas
what happens when bladder is full but can’t go to the toilet
- 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) !!
what is the cerebral aqueduct
surrounded by periaqueductal grey (PAG)
important sensory anf motor relay station
various clinical situations where nerves control micturition
- 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
foetal urination
- 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
what happens if there is insufficient urine in amnion fluid
- under developed lungs - fatal
- causes contractures and club feet
- renal agenesis - baby has no kidneys and not surrounded by enough amnotic fluid -malformed lungs
Pseudoglandular phase
7th to 17th week
by 8th week 17 orders of branching
formation of bronchial tree up to terminal bronchioles
what produced amniotic fluid
Broncho pulmonary epithelium
involuntary micturition reflex
- stretch receptors detect filing of bladder - transmit afferent signals to spinal cord
- signals return to bladder from SC segments S2 and S3 via parasympathetic fibres in pelvic nerve
- efferent signals excite detrusor muscles
- efferent signals relax internal urethral sphincter - urine is involuntary folded if not inhibited by brain
micturition reflex voiding - nappy change what can urination be triggered by
- suprapubic percussions
- thigh scratching
- touching penile skin
- pulling pubic hair
nerves of micturition reflex
- 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
Voluntary control of micturition
- 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
why do children wet the bed
- 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
emptying urine from ale urethra
- Use bulbospongious muscle to empty the final 5% of wine from the bladder
- supplied by the somatic pudendal nerve
why can’t you urinate during an erection
- 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
ejacuation para or sympathetic
ejaculation = sympathetic activity
ejaculation
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
Autonomous bladder
- 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
Atonic bladder
- 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
Automatic reflex bladder in adults
- after atonic bladder stage
( similar to in babies )
every 1- 4 hours
involuntary micturition reflex
- stretch receptors detect filling og bladder
transmit afferent signals to SC - signals return to bladder from SC segments S2 and S3 via parasympathetic fibres in pelvic nerve
- efferent signals excite detrusor muscle
- efferent signals relax internal urethral sphincter
urine is involuntary voided if not inhibited by brain
dementia - micturition
- 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
apraxia
difficulty of undressing and using toilet
