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Physiology 1 : renal > Micturition > Flashcards

Micturition Flashcards

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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
What is the lining of the bladder?
→ transitional epithelium
26
What is the bladder muscle?
→ Detrusor
27
What is the bladder permeable and impermeable to?
→ Impermeable to salt and water | → Permeable to lipophilic molecules
28
What do the neural circuits of the bladder act like?
→ an on and off switch to alternate between storage and elimination
29
What is the lower urinary tract innervated by?
→ 3 sets of peripheral nerves → Parasympathetic (pelvic) → Sympathetic ( hypogastric) → Somatic nervous system ( pudendal)
30
What are the two bladder innervations?
→ Sensory | → Motor
31
What does sensory innervation do?
→ Gives a sensation of fullness
32
What does motor innervation do?
→ Causes contraction and relaxation of detrusor muscle and external sphincter to control micturition
33
Where does the parasympathetic motor innervation go from and to?
→ 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
Where does the sympathetic motor neurons go from and to?
→ 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
Where do the somatic neurons go from and to?
→ S2 - S4 | → innervate the external sphincter
36
What is the innervation of the detrusor muscle like?
→ 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
What do ACh and ATP do to the detrusor?
→ cause it to contract
38
What receptor does ATP act on?
→ Purinergic
39
What inhibits detrusor contraction?
→ Atropine
40
What causes the detrusor to relax?
→ Noradrenaline → Inhibits transmission at parasympathetic ganglia indirectly → Directly via beta receptors
41
What relaxes the internal sphincter?
→ NO and ACh | → Noradrenaline
42
What holds the external sphincter closed?
→ ACh (tonic and continual)
43
What effects do the parasympathetic neurons have?
→ Contract detrusor - ACh (muscarinic) and ATP (purigenic) → Relax internal sphincter - via NO (cGMP) & ACh
44
What effects do sympathetic neurons have?
→ Relax detrusor - indirectly via NA & directly via Beta receptors → Contract the internal sphincter - NA (alpha receptors)
45
What effects do the somatic neurons have?
→ Contract the external sphincter | - ACh
46
What is the main afferent pathway?
→ Via the pelvic nerve | → Small myelinated A delta fibres → micturition reflex
47
What are A delta fibers linked with?
→ Stretch receptors - wall tension | → Volume receptors - bladder filling
48
Where are Unmyelinated C fibres found?
→ near the epithelium
49
What are unmyelinated C fibres linked with?
→ Nociceptors - pain
50
What are hypogastric and pudendal pathways linked with?
→ Nociceptors | → Flow receptors
51
What do A fibres sense?
→ Tension in detrusor → Detrusor contraction → bladder fullness - discomfort
52
What do C fibres sense?
→ Respond to damage | → Inflammatory mediators
53
How does the bladder fill (flowchart)?
``` Initally bladder is empty - sphincters closed ↓ bladder pressure low ↓ arrival of urine ↓ detrusor relaxes progressively ↓ little increase in pressure ↓ sphincters still closed ```
54
When do we become conscious of bladder filling?
→ 100-150ml
55
When does discomfort begin?
→ 300-400
56
What kind of a reflex is micturition?
→ Autonomic
57
How is the micturition reflex modified?
→ By voluntary control | → Inhibited by higher centres in the brain
58
What disrupts voluntary control of micturition?
→ Disease/injury/ageing → Bladder hyperactivity + urge incontinence → Stress incontinence
59
Flow chart of micturition
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
What is the PMC?
→ Pontine micturition centre
61
How can higher centres modify micturition reflexes?
→ Contract external sphincter and levator muscle
62
What can the urine stream be stopped by?
→ Strangury 'urethral pain' due to urethritis → Pinching glans penis → at night if bladder fills to capacity PMC wakes you up
63
Flow chart of innervation to bladder
``` Cerebral cortex (frontal lobe) ↓ Brain stem ↓ Spinal tract ↓ Spinal efferents ↓ Ganglion ↓ Bladder ```
64
What sends signals from the bladder to the spinal efferents?
→ C unmyelinated afferent
65
What sends signals from the bladder to the spinal tract?
→ A delta myelinated afferent
66
Where is the bladder?
→ Floor of abdominal cavity
67
What helps to compress the urethra?
→ Reflex contraction of periurethral striated muscles
68
What is the result of contracting abdominal muscles?
→ Increased intra-abdominal pressure transmitted to the bladder and urethra
69
Why do you have to completely empty the bladder?
→ Restore sterility → Bacteria in retained urine seeds fresh urine → Retained urine - UTI
70
What can repeated infections do to kidney function?
→ destroy renal function
71
What is a UTI?
→ Urinary tract infection that can happen anywhere along the urinary tract
72
What is an infection in the bladder called?
→ Cystitis
73
What is an infection of the kidneys called?
→ Pyelonephritis
74
What is a urethra infection called?
→ Urethritis
75
What are risk factors for a UTI?
``` → pregnancy → Enlarged prostate → Kidney stones → bowel incontinence → old age ```
76
What are the problems of an ageing bladder?
→ Prostate enlargement Incontinence - weakening of sphincters → Overactive bladder
77
What is a consequence of slow urine stream?
→ Incomplete emptying | → Infection
78
What are medications for incontinence?
→ anti muscarinics → detrusor relaxes → relax smooth muscle
79
What is bladder retraining?
→ Kegel exercises
80
What surgery can be carried out for the bladder?
→ Bladder neck suspension | → collagen injections
81
What is SNS?
→ sacral nerve stimulation | → electrical impulses to sacral nerve

Physiology 1 : renal (13 decks)

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