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Physiology 1 : renal > Micturition > Flashcards

Micturition Flashcards

1
Q

What is micturition?

A

→ Act of urination

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2
Q

What are the basic processes of micturition?

A

→ Made in the kidneys
→ Urine stored in bladder
→ Urine released from bladder

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3
Q

Where does the urine pass from and to?

A

→ From collecting duct of renal tubules into renal pelvis

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4
Q

What aids the movement of the urine into the ureter?

A

→ Contraction of the smooth muscle of the pelvis

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5
Q

What pressure do the ureters squeeze urine to?

A

→ 10-20 mmHg

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6
Q

How do the ureters open into the bladder and why?

A

→obliquely

→ Prevents reflux of urine back into ureters by passive flap-wave

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7
Q

What type of peristalsis is the ureter under?

A

→ Myogenic in origin and not under CNS control

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8
Q

What do kidney stones form from?

A

→ Crystals that separate from urine within urinary tract

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9
Q

What does urine contain to prevent kidney stones?

A

→ citrate

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10
Q

What do kidney stones usually contain?

A

→ Calcium

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11
Q

Why are kidney stones more common in men?

A

→ Due to testosterone

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12
Q

What are kidney stones caused by?

A 
→ Poor urine output
→ Obstruction 
→ Altered urinary pH 
→ Low concentration of inhibitors 
→ Infection
→ Dietary intake of stone forming substances
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13
Q

Where can kidney stones form?

A

→ In the kidney
→ Ureter
→ Bladder

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14
Q

What are symptoms of kidney stones?

A

→ Dysuria
→ Haematuria
→ Pain
→ Reduced urine flow
→ Urinary tract obstruction - pressure reaches 50 mmHg
→ If stone is at tip of urethra- pain inhibits micturition

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15
Q

How much urine can the bladder hold without pressure?

A

→ 400ml without much pressure

→ Due to the spherical structure

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16
Q

What can the transitional epithelium do?

A

→ stretches without damage

→ has ridges that flatten out as the bladder fills

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17
Q

What allows separation of urine and blood in the bladder?

A

→ Impermeable to salts and water

→ No exchange between urine and capillaries of bladder wall

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18
Q

What is the muscle coat around the epithelium called and made from?

A

→ detrusor muscle

→ made from bundles of smooth muscle interlacing

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19
Q

What does the trigone region contain?

A

→ Opening of ureter

→ neck of urethra

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20
Q

What are the sphincters in the bladder?

A

→ Internal - extension of detrusor - NOT VOLUNTARY

→ External - 2 striated muscles

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21
Q

What is the external sphincter composed of?

A

→ 2 striated muscles
→ (compressor urethrae and bulbocavernosus surrounding urethra)
→ Responsible for continence - conscious, voluntary control

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22
Q

What is the internal sphincter formed from?

A

→ Loop of muscle that is an extension of the detrusor

→ When detrusor contracts the fibers forming the loop shorten and open the sphincter

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23
Q

What is the arrangement of the female bladder?

A

→ Short urethra - only carries urine

→ External sphincter poorly developed - prone to incontinence after childbirth

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24
Q

What is the arrangement of the male bladder?

A

→ Urethra carries urine and semen

→ urine elimination is aided by the contraction of bulbocavernosus muscle

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25
Q

What is the lining of the bladder?

A

→ transitional epithelium

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26
Q

What is the bladder muscle?

A

→ Detrusor

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27
Q

What is the bladder permeable and impermeable to?

A

→ Impermeable to salt and water

→ Permeable to lipophilic molecules

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28
Q

What do the neural circuits of the bladder act like?

A

→ an on and off switch to alternate between storage and elimination

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29
Q

What is the lower urinary tract innervated by?

A

→ 3 sets of peripheral nerves
→ Parasympathetic (pelvic)
→ Sympathetic ( hypogastric)
→ Somatic nervous system ( pudendal)

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30
Q

What are the two bladder innervations?

A

→ Sensory

→ Motor

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31
Q

What does sensory innervation do?

A

→ Gives a sensation of fullness

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32
Q

What does motor innervation do?

A

→ Causes contraction and relaxation of detrusor muscle and external sphincter to control micturition

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33
Q

Where does the parasympathetic motor innervation go from and to?

A

→ Sacral region of spinal cord S2- S4
→ Pre synaptic neurons synapse to post ganglionic neurons in the bladder wall
→ Synapse in the internal sphincters

34
Q

Where does the sympathetic motor neurons go from and to?

A

→ lumbar region T-11 - L2
→ innervate onto post synaptic neurons in the hypogastric ganglia
→ Innervate directly to the internal sphincter
→ inhibiting the parasympathetic system

35
Q

Where do the somatic neurons go from and to?

A

→ S2 - S4

→ innervate the external sphincter

36
Q

What is the innervation of the detrusor muscle like?

A

→ Parasympathetic pre ganglion synapse onto post ganglion neurons in the bladder wall
→ release AcH
→ acts on nicotinic receptors
→ the post ganglionic neurons release AcH and ATP

37
Q

What do ACh and ATP do to the detrusor?

A

→ cause it to contract

38
Q

What receptor does ATP act on?

A

→ Purinergic

39
Q

What inhibits detrusor contraction?

A

→ Atropine

40
Q

What causes the detrusor to relax?

A

→ Noradrenaline
→ Inhibits transmission at parasympathetic ganglia indirectly
→ Directly via beta receptors

41
Q

What relaxes the internal sphincter?

A

→ NO and ACh

→ Noradrenaline

42
Q

What holds the external sphincter closed?

A

→ ACh (tonic and continual)

43
Q

What effects do the parasympathetic neurons have?

A

→ Contract detrusor
- ACh (muscarinic) and ATP (purigenic)
→ Relax internal sphincter
- via NO (cGMP) & ACh

44
Q

What effects do sympathetic neurons have?

A

→ Relax detrusor
- indirectly via NA & directly via Beta receptors
→ Contract the internal sphincter
- NA (alpha receptors)

45
Q

What effects do the somatic neurons have?

A

→ Contract the external sphincter

- ACh

46
Q

What is the main afferent pathway?

A

→ Via the pelvic nerve

→ Small myelinated A delta fibres → micturition reflex

47
Q

What are A delta fibers linked with?

A

→ Stretch receptors - wall tension

→ Volume receptors - bladder filling

48
Q

Where are Unmyelinated C fibres found?

A

→ near the epithelium

49
Q

What are unmyelinated C fibres linked with?

A

→ Nociceptors - pain

50
Q

What are hypogastric and pudendal pathways linked with?

A

→ Nociceptors

→ Flow receptors

51
Q

What do A fibres sense?

A

→ Tension in detrusor
→ Detrusor contraction
→ bladder fullness - discomfort

52
Q

What do C fibres sense?

A

→ Respond to damage

→ Inflammatory mediators

53
Q

How does the bladder fill (flowchart)?

A 
Initally bladder is empty - sphincters closed 
↓
bladder pressure low 
↓
arrival of urine 
↓
detrusor relaxes progressively 
↓
little increase in pressure 
↓
sphincters still closed
54
Q

When do we become conscious of bladder filling?

A

→ 100-150ml

55
Q

When does discomfort begin?

A

→ 300-400

56
Q

What kind of a reflex is micturition?

A

→ Autonomic

57
Q

How is the micturition reflex modified?

A

→ By voluntary control

→ Inhibited by higher centres in the brain

58
Q

What disrupts voluntary control of micturition?

A

→ Disease/injury/ageing
→ Bladder hyperactivity + urge incontinence
→ Stress incontinence

59
Q

Flow chart of micturition

A

As receptors detect tension
↓
transmit information via afferents ( A delta system) to the spinal cord
↓
synapse to parasympathetic efferents to override storage
↓
detrusor contracts and internal sphincter relaxes
↓
bladder constricts
↓
urine forced out and activates flow receptors in the urethra
↓
activates flow receptors in urethra
↓
pudendal afferents are excited and switch off the tonic system
↓
Tonic contraction removed by inhibition of somatic input

60
Q

What is the PMC?

A

→ Pontine micturition centre

61
Q

How can higher centres modify micturition reflexes?

A

→ Contract external sphincter and levator muscle

62
Q

What can the urine stream be stopped by?

A

→ Strangury ‘urethral pain’ due to urethritis
→ Pinching glans penis
→ at night if bladder fills to capacity PMC wakes you up

63
Q

Flow chart of innervation to bladder

A 
Cerebral cortex (frontal lobe) 
↓
Brain stem
↓
Spinal tract
↓
Spinal efferents
↓
Ganglion
↓
Bladder
64
Q

What sends signals from the bladder to the spinal efferents?

A

→ C unmyelinated afferent

65
Q

What sends signals from the bladder to the spinal tract?

A

→ A delta myelinated afferent

66
Q

Where is the bladder?

A

→ Floor of abdominal cavity

67
Q

What helps to compress the urethra?

A

→ Reflex contraction of periurethral striated muscles

68
Q

What is the result of contracting abdominal muscles?

A

→ Increased intra-abdominal pressure transmitted to the bladder and urethra

69
Q

Why do you have to completely empty the bladder?

A

→ Restore sterility
→ Bacteria in retained urine seeds fresh urine
→ Retained urine - UTI

70
Q

What can repeated infections do to kidney function?

A

→ destroy renal function

71
Q

What is a UTI?

A

→ Urinary tract infection that can happen anywhere along the urinary tract

72
Q

What is an infection in the bladder called?

A

→ Cystitis

73
Q

What is an infection of the kidneys called?

A

→ Pyelonephritis

74
Q

What is a urethra infection called?

A

→ Urethritis

75
Q

What are risk factors for a UTI?

A 
→ pregnancy 
→ Enlarged prostate
→ Kidney stones
→ bowel incontinence
→ old age
76
Q

What are the problems of an ageing bladder?

A

→ Prostate enlargement

Incontinence - weakening of sphincters
→ Overactive bladder

77
Q

What is a consequence of slow urine stream?

A

→ Incomplete emptying

→ Infection

78
Q

What are medications for incontinence?

A

→ anti muscarinics
→ detrusor relaxes
→ relax smooth muscle

79
Q

What is bladder retraining?

A

→ Kegel exercises

80
Q

What surgery can be carried out for the bladder?

A

→ Bladder neck suspension

→ collagen injections

81
Q

What is SNS?

A

→ sacral nerve stimulation

→ electrical impulses to sacral nerve

Physiology 1 : renal (13 decks)

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