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Bmsc 208 > Renal 4 > Flashcards

Renal 4 Flashcards

1
Q

what is clearance

A

rate at which a solute disappears from the body by excretion or metabolism

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2
Q

clearance of x(ml/min)=

A

excretion rate of x (mg/min)/ (x) plasma (mg/ml)

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3
Q

clearance is expressed as what

A

the volume of plasma passing through the kidneys that has been totally cleared of solute in a given period of time (usually min)
- blood cleared of solute

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4
Q

1mg of solute Z in 100ml of plasma, found 0.5mg of Z appearning in urine/min

A

clearance of z= 0.5mg/min / 1mg/ml
= 50ml/min
- kidneys removes all solute Z in 50ml of plasma in one minute

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5
Q

how do we most accurately calculate GFR

A

look at clearance of substance that is freely filtered and neither reabsorbed or secreted

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6
Q

what is perfect molecule to measure clearance

A

inulin
- method is impractical

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7
Q

what is inulin

A

polysaccharide found in isolated nephrons to be completely filtered and not reabsorbed

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8
Q

what do clinicians commonly use to measure GFR and renal function

A

creatinine clearance

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9
Q

Why is creatinine not the most accurate

A

freely filtered but is also secreted in very small amounts
- slightly overestimates GFR

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10
Q

person has plasma creatinine conc. of 0.01mg/ml and an excretion rate of 1.25mg/min

A

1.25mg/min / 0.01 mg/ml = 125 ml/min

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11
Q

once we know an individuals GFR what can we look at

A

how their kidneys handle any filtered solute by measuring the solutes plasma conc. and excretion rate (collecting urine and blood)

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12
Q

filtered load of X=

A

[x]plasma x GFR

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13
Q

how can we tell how the nephron handled the substance

A

comparing the filtered load with its excretion rate

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14
Q

if less substance appears in the urine then filtered,

A

net reabsorption has occured

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15
Q

if more appears in the urine than was filtered,

A

net secretion has occured

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16
Q

what else can we compare GFR to

A

clearance of a solute

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17
Q

what is renal clearance

A

non-invasive method using collected urine and blood

18
Q

what is purpose of renal clearance

A
  1. calculate GFR - if substance is filtered, not reabsorbed nor secreted (filtered=excreted)
  2. understand the net renal handling of any filtered solute
19
Q

if clearance of a substance is less than GFR

A

Net reabsorption

20
Q

if clearance of a substance is greater than GFR,

A

net secretion has occurred

21
Q

what does comparison of clearance values only give you

A

net handling of a solute
- net reabsorption or net secretion

22
Q

GFR=clearance
Filtered=excreted

A

filtered, not reabsorbed, not secreted

23
Q

GFR>clearance
filtered>excreted
e.g., urea and glucose

A

filtered and net reabsorption

24
Q

GFR<Clearance
filtered<excreted
e.g., penicillin

A

filtered and net secretion

25
Q

what does filling of the bladder activate

A

stretch receptors initiating micturition reflex

26
Q

what is the pathway from kidney to external environment

A

collecting duct - renal pelvis - ureters - urinary bladder - urethra

27
Q

what do ureters undergo

A

rhythmic contractions (pacemaker cells)

28
Q

what is bladder made up of

A

smooth muscle
detrusor muscle

29
Q

what sphincter is at bottom of bladder

A

internal sphincter (smooth muscle)
passive

30
Q

what is external sphincter made of

A

skeletal muscle, stays contracted, tonic motor output

31
Q

when will you be consciously aware you must urinate

A

200ml

32
Q

as filling exceeds 200ml what happens

A

walls will distend and stretch receptors will fire

33
Q

sensory input by stretch receptors activate what

A

parasympathetic neurons fire

34
Q

what do parasympathetic neurons activate

A

detrusor muscle contracts and internal sphincter is passively pulled open, external relaxes

35
Q

what happens if not right time to urinate

A

descending outputs inhibit reflex and inhibit parasympathetic

36
Q

once exceeding 500ml what happens

A

internal sphincter forced open, leading to reflexive opening of external sphincter and loss of voluntary opposition

37
Q

what is left in bladder after micturition

A

10ml

38
Q

where does sensory info of micturition reflex feed back to

A

sacral region of spinal cord and brainstem and cerebral cortex

39
Q

incontinence

A

inability to control urination voluntarily

40
Q

causes of incontinence

A
  • infants- corticospinal connections not yet been established
  • damage to internal or external sphincter
  • spinal cord damage
  • aging (loss of muscle tone, stroke, alzeihmers, prostate growth)
41
Q

what are 4 parameters the homeostatic mechanisms for fluid/electrolyte balance focus on

A
  1. fluid volume
  2. osmolarity
  3. concentrations of individual ions
  4. pH

Bmsc 208 (33 decks)

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