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RENAL PHYSIOLOGY > Renal Assessment and Micturition > Flashcards

Renal Assessment and Micturition Flashcards

1
Q

When is the measurement of GFR useful?

A

Assessment of renal disease in nephron damage/disease Awareness when giving renal excreted drugs

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2
Q

What is total GFR?

A

Sum of all filtration by function of nephrons

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3
Q

What is the plasma plasma clearance formula (for substance x)?

A

Clearancex = [Urinex] x Urine flow rate/[plasmax]

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4
Q

What is the gold standard for clearance measurement?

A

Inulin clearance - loading dose given

Give time for equilibrium to be reached

Simultaneous plasma and (timed) urine measurement

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5
Q

What is plasma clearance?

A

The amount of plasma free of substance

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6
Q

Why is inulin used for true GFR measurement?

A

O% reabsorbed = 100% excreted

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7
Q

What clearance do substances filtered and reabsorbed have, relative to inulin?

A

Lower clearance because some will be taken back into the plasma

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8
Q

What clearance do substances filtered and secreted have, relative to inulin?

A

Higher clearance because the concentration in the urine will be lower

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9
Q

What is the change in GFR through life?

A

Decrease by 1ml/min/year after 30

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10
Q

What substance is used instead of inulin?

A

51Cr-EDTA

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11
Q

How is creatinine produced?

A

Endogenous breakdown of Creatine by muscles

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12
Q

eGFR is taken as what?

A

(estimate)GFR = 1/[PCR]

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13
Q

Why does eGFR lack accuracy?

A

GFR can be halved before PCR is elevated

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14
Q

What factors affect serum creatinine?

A

Muscle mass

Dietary intake

Drugs

Ketoacidosis

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15
Q

What is the normal clearance of glucose?

A

Zero - as it is all reabsorbed

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16
Q

What is the normal clearance of urea?

A

50mL/min as 50% is excreted

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17
Q

What is the use of PAH clearance?

A

Measure of real plasma flow

Measure of all plasma flowing through kidneys at any one time

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18
Q

What is PAH?

A

Para-amino-hippuric acid

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19
Q

What is PAH clearance used for?

A

Measure real plasma flow

Measure of all plasma flowing through kidneys at any one time

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20
Q

Why is PAH clearance used?

A

PAH is freely filtered at glomerulus

Remainder is actively secreted into tubule

90% of plasma PAH is cleared

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21
Q

What is a normal real plasma flow?

A

660mls/min

22
Q

Why does penicillin has a greated clearance than inulin?

A

Because its filtered AND excreted

23
Q

How does urine flow from kidneys to bladder?

A

Peristaltic contraction of smooth muscles of the ureters

24
Q

How does urine enter the bladder? Why is this important?

A

Enters at an oblique angle

Prevents reflux of urine into the ureters

25
Q

What is the name of the muscles of bladder contraction

A

Detrusor muscles

26
Q

What is the structure of the internal urethral sphincter?

A

NOT true sphincter

Smooth muscle acts as sphincter when relaxed

27
Q

What is the structure of the external urethral sphincter?

A

True sphincter

Skeletal muscle under voluntary somatic control

28
Q

What epithelium lines the bladder?

A

Transitional of ureter

29
Q

The three openings of the bladder make up which structure?

A

Trigone of bladder

30
Q

What openings make up the trigone of bladder?

A

2 Vesicoureteric openings

Urethral opening

31
Q

What is the structure of the pressure-volume curve of the bladder?

A

Long flat segment as initial increments of urine enter bladder

Sharp rise as micturition reflex is triggered

32
Q

What is a typical, temperate climate normal daily urine production?

A

750-2500mls

33
Q

What is the passive state of the internal urethral sphincter?

A

Passively contracted

34
Q

How is the bladder innervated?

A

Parasympathetic - Pelvic nerves S2-S4

Sympathetic supply - inhibit bladder contraction, close internal sphincter (L1-L3)

Somatic motorneurones (pudendal nerves) innervate skeletal muscle

35
Q

What is the role of parasympathetic innervation of the bladder?

A

Increased activity = increased contraction of the detrusor muscle

Increases pressure within the bladder

36
Q

What is the role of sympathetic innervation of the bladder?

A

Prevent reflux of semen back into the bladder during ejaculation

Inhibit bladder contraction

Close internal urethral sphincter

37
Q

What is the role of somatic innervation of the bladder?

A

Motor control - contraction of the external urethral sphincter against bladder contractions

38
Q

What is the sensory innervation of the bladder?

A

Stretch receptor afferents (↑ discharge as bladder fills)

39
Q

↑ sensory discharge as bladder fills triggers what?

A

Via interneurones:

  • Excitation of parasympathetic outflow
  • Inhibition of sympathetic outflow
  • Inhibition of somatic motorneurones to external sphincter
  • Pathways to sensory cortex = sensation of fullness
40
Q

Why do babies pee themselves?

A

Sensory interneurones causing excitation of parasympathetic bladder innervation, and inhibition of somatic motorneurones to external sphincter causes micturition

But the little fucker hasnt learned to control it yet

41
Q

What volume of urine is required to initiate the spinal reflex in adults?

A

300 - 350mls

42
Q

Micturition delay is accomplished how?

A

Descending pathways (from cortex, brainstem)

Inhibit parasympathetic
Stimulate somatic nerves of external sphincter and override stretch receptor input

43
Q

Voluntary initiation of micturition involves which descending pathways?

A

Stimulation of parasympathetic contraction of the detrusor muscles

Inhibition of somatic motorneurones controlling external sphincters

44
Q

Which muscles are used to initiate contraction of detrusor muscles in voluntary urination?

A

Contraction of pelvic floor muscles tugging on detrustor muscles

45
Q

What muscles are used in interrupting urine flow through the urethra?

A

Perineal muscles

External sphincter muscles

46
Q

How do females empty the urethra in urination?

A

Gravity

47
Q

How do males empty the urethra after urination?

A

Contractions of the bulbocavernosus muscle

48
Q

Which types of neural lesions cause abnormalities in micturition?

A
  1. Interruption of afferent nerves
  2. Interruption of both afferent and efferent nerves
  3. Interruption of fascilitatory/inhibitory descending pathways from brain
49
Q

How do paraplegic patients “learn” to initiate voiding?

A

Mild mass reflex - pinch/stroking thigh

50
Q
A

RENAL PHYSIOLOGY (10 decks)

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