Neural Control of Micturition Flashcards

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1
Q

What type of control is micturition

A

Autonomic and Voluntary

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2
Q

How can micturition be described?

A

a spinal reflex that is inhibited or facilitaed by higher brain centres

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3
Q

What are the bladders two modes

A

storage and elimination

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4
Q

what is the shape of the bladder

A

triangular pyramid shape

1 base, 1 superior and 2 inferolateral sides

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5
Q

which muscles control micturition (4)

A

Detrusor (bladder wall)

Internal urethral sphincter

External urethral sphincter

Bulbospongiosus (gets last bit out of the pipe)

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6
Q

what is the capacity of the bladder

A

500ml

1st voiding urge at 150ml

fullness felt at 400ml

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7
Q

What does the PMC (pontine micturition centre) do

A

acts as a relay station for ascending spinal bladder information (from stretch mechanoreceptors)

neuronal silence = bladder empty

to urinate relaxes external urethral sphincter while contracting of the detrusor muscles

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8
Q

What does the PAG (periaqueductal grey) do

A

acts as important sensory & motor relay station

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9
Q

What is amnion fluid made of

A

mostly urine and small extent from lungs

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10
Q

what are uterus conditions like for the foetus

A

8 months drinking urine/faeces & inhaling

insufficient urine under develops the lungs & can cause contractures & club feet

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11
Q

what happens to the lungs during pseudo glandular phase

A

formation of bronchial tree to terminal bronchioles

Broncho-pulmonary epithelium begins to produce amniotic fluid

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12
Q

what happens if the foetus stops urinating

A

renal agenesis - can be fatal baby will be born with 1 or no kidneys

less amnion fluid means only the placenta is keeping them alive

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13
Q

How does the involuntary micturition reflex work

A

stretch receptors detect full bladder

efferent signals returned from spinal cord S2/S3 excite detrusor muscles

and relax internal urethral sphincter

if not inhibited by the brain urine will be voided

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14
Q

what can trigger micturition reflex voiding?

A

suprapubic percussions

thigh scratching

touching penile skin

pulling pubic hair

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15
Q

how does voluntary control of micturition work?

A

stretch receptors signal

if it is not time to urinate cerebrum excites spinal interneurons to keep external sphincter contracted

when it is time cerebrum inhibits sacral neurons that keep the sphincter closed

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16
Q

why do babies wet the bed?

A

stretch sensory information from the bladder doesn’t wake the baby

brain doesn’t not inhibit the external sphincter so automatic reflex takes place

17
Q

Why is hard to urinate with an a erection?

A

parasympathetic nerves allow urination and erection but cannot be done at same time

prevents urination during intercourse

during ejaculation (sympathetic) pressure in the urethra over-powers the corpus spongiosum

18
Q

how does ejaculation occur

A

sympathetic nerves cause the following

detrusor muscles relax

contracts internal urethral sphincter

pudendal nerve contracts the bulbocavernosus muscle

net result: prevents semen escaping into bladder

19
Q

what happens to cause an autonomous bladder

A

the loss of sacral nerves (parasympathetic & pudendal)

sympathetic nerve remains unopposed causing detrusor to relax and internal sphincter to contract causing backfill

20
Q

what causes atonic bladder

A

when spinal cord is damaged (lasts days-weeks) detrusor muscles relax and internal sphincter contracts - urine is retained and patient may not realise

21
Q

how does dementia effect micturition

A

50% of nursing home patients have bladder control issues

difficulty of cerebrum interpretation

harder to find toilet and hold it in while doing so

apraxia - difficulty undressing/using toilet