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Renal I Midterm > Lecture 7: Renal Blood Flow > Flashcards

Lecture 7: Renal Blood Flow Flashcards

1
Q

What are the normal and dysfunction levels for BUN?

A

10:1 = Normal = Normal filtering GFR

>20:1 = Decreased GFR = Pre-Kidney failure

<10:1 = Full kidney failure

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2
Q

If you are not given the glucose or BUN concentrations how do you calculate Osmolality?

A

Osmolality = (2 x sodium)

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3
Q

Total renal blood flow is approximately what percentage of resting cardiac output?

A

20%

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4
Q

How many liters of filtrate are produced per day?

A

180 L

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5
Q

Substances leaving the plasma must pass through filtration barriers before entering the tubule lumen, what are they?

A

1) Glomerular capillary endothelium (pores)
2) Basal lamine (acellular basement membrane)
3) Filtration slits between the pedicles of the podocytes in the inner layer of Bowman’s capsule

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6
Q

What is found on the glomerular capillary wall epithelium; how does this affect permability compared to other capillaries?

A
  • Many large pores between enodthelial cells
  • Many large holes (fenestrations) in the endothelial cells

* 100x more permeable to H2O and solutes than other capillaries

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7
Q

What is the largest protein we want filtering throught the Bowman’s capsule and approximately what percent gets through?

A
  • Albumin (smallest plasma protein)
  • <1%
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8
Q

What 2 factors constitue the selectivity of the basment membrane to particle movement?

A
  • Size of particle
  • Charge of particle
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9
Q

What causes the negatively charged molecules to be repelled from filtration barrier; found in which layers?

A

Glycoproteins in basement membrane and podocytes

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10
Q

Basment membrane prevents molecules larger than what from passing through?

A

7 nm or no greater than 40,000 daltons

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11
Q

Discuss the filtraton differences of postive, neutral, and negatively charged molecule?

A

Positive: More filtered

Neutral: In the middle

Negative: Less filtered

*Notice the filtration rate as size changes for each

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12
Q

What is Hematuria and what is it indicative of?

A
  • RBC’s in the urine
  • Indicative of renal or kidney diseases/presence of kidney stones
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13
Q

How much protein is normally excreted in the urine daily, what is it called when more than this value is excreted?

A
  • 150 mg
  • Proteinuria = >150 mg excreted
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14
Q

What causes albuminuria?

A

Due to disruption of the negative charges (glycoproteins) within the basement membrane.

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15
Q

What are Tamm-Horsfall proteins; derived from?

A

Low-molecular weight proteins (LMWP) derived from the cells of Thick-ascending limb, accounts for 25 mg of daily protein excretion

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16
Q

Function of Podocytes?

A
  • Structural support for basement membrane
  • Repel negatively charged plasma proteins
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17
Q

Podocyte damage is commonly referred to as what syndrome; does this cause renal failure?

A
  • Nephrosis
  • Usually does not cause renal failure initially. Damage disrupts the relationship between podocytes and basement membrane = loss of strucutral support
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18
Q

The juxtaglomerular apparatus is made up of what 2 cells types?

A

1) Macula Densa (sensor cells)
2) Juxtaglomerular cells (aka granular cells) - renin

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19
Q

What do the Macula densa cells sense?

A
  • Salt content
  • Fluid volume
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20
Q

What 2 things do the Macula densa cells do if they sense LOW salt and LOW fluid volume?

A

1) Tell the granular cells (juxtaglomerular) to release renin
2) Dilate the afferent arterioles of the glomerulus = increased glomerular hydrostatic pressure

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21
Q

The juxtaglomerular cells secrete renin in response to what 3 things?

A

1) Beta-adrenergic stimulation
2) Decreased renal perfusion pressure
3) Signals from the Macula densa

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22
Q

What causes juxtaglomerular cells to release renin?

A

Decreased renal arterial pressure = Decreases stretch = decreased intracellular calcium concentration.

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23
Q

What are the 3 major mechanisms for the regulation of renin release?

A

1) Perfusion pressure (low = renin release)
2) Sympathetic nerve activity (activation = renin release)
3) NaCl delvivery to macula densa (low = renin release)

24
Q

What is Tubuloglomerular feedback?

A

When NaCl is decreased (sensed by Macula densa), Renin secretion is stimulated and vice versa.

25
Q

If the blood flow or blood pressure in the afferent arterioles decreases for any reason, what is stimulated?

A

Renin-angiotensin-aldosterone triad (RAAS)

26
Q

What is the function of renin?

A

Converts angiotensinogen —> angiotensin I

27
Q

Which hormone does angiotensin stimulate the secretion of; and its function?

A
  • Aldosterone
  • Increases the reabosrption of Na and H2O to increase blood volume, thus increasing BP
28
Q

Angiotensin I is converted to what, by what enzyme; function of its converted form?

A
  • Angiotensin II by ACE
  • Causes system vasoconstriction in attemp to increase BP
29
Q

How does a Beta-blocker affect renin levels?

A

Decreases Renin

30
Q

What are the 3 things that ultimately determine GFR?

A

1) Renal blood flow
2) Resistance to flow
3) Permeability of glomerular basement membrane

31
Q

What is the GFR value for normal, kidney disease, and kidney failure?

A

Normal: 60-120

Kidney disease: 15-60

Kidney failure: 0-15

32
Q

What kind of molecules are free to pass from blood into the glomerular capsule?

A

Glucose, amino acids, water, and nitrogenous wastes

33
Q

Keeping larger plasma proteins in the capillaries maintains which pressure; prevents what from occuring

A

Colloid osmotic pressure of the glomerular blood (πG); prevents the loss of all its water to the renal tubules

34
Q

What is the net filtration pressure equation (think Starling)?

A

GFR = Kf (PG - PB - πG + πB)

35
Q

What is the normal value of Bowman’s space (capsular) oncotic pressure (πB)?

A

Zero! Glomerular filtrate should contain little to no proteins

36
Q

Vasoconstriction of the afferent arteriole does what to GFR and GHP?

A

Decrease GFR and GHP

37
Q

Vasodilation of the afferent arteriole does what to GFR and GHP?

A

Increase GFR and GHP

38
Q

Vasodilation of the efferent arteriole does what to GFR and GHP?

A

Decreases GFR and GHP

39
Q

Vasoconstriction of the efferent arteriole does what to GFR and GHP?

A

Increases GFR and GHP

40
Q

Decrease Kf and GFR are caused by what pathologies?

A

Renal disease, diabetes, HTN

41
Q

Increased PB (Bowman’s capsule hydrostatic pressure) and decreased GFR caused by what pathologies?

A

Urinary tract obstruction (i.e kidney stones)

42
Q

Increased πG and decreased GFR caused by what pathologies?

A

Decreased renal flow, increased plasma proteins

43
Q

The GFR increases mainly as a result of decreased what (think autonomics)?

A

Sympathetic nerve activity

44
Q

What 4 changes can lead to edema?

A
  • Increased capillary hydrostatic pressure (heart failue)
  • Decreased plasma oncotic pressure (hypoproteinemia)
  • Increased capillary permeability (histamine/bradykinin)
  • Lymphatic obstruction
45
Q

What 2 drugs decrease GFR, how?

A

1) NSAIDs: afferent vasocontriction
2) ACE inhibitors: decrease efferent vasoconstriction

46
Q

What 4 drugs increase GFR, how?

A

1) Prostaglandins: vasodilator (afferent>efferent)
2) Angiotensin II: vasoconstrictor (efferent > afferent)
3) Norepi: vasoconstrictor (efferent), increases BP
4) ANP: afferent vasodilator, efferent vasoconstrictor

47
Q

What kind of receptors for sympathetic innervation are found on the: afferent arteriole, JG apparatus, and collecting duct; which NT acts on them all?

A

Afferent: Alpha-1 (vasoconstriction)

JG apparatus: Beta-1 (renin secretion)

Collecting Duct: Alpha-1 (sodium reabsorption)

*The NT is norepinephrine

48
Q

When is autoregulation functioning to maintain constant GFR; what MAP?

A
  • Under normal conditions
  • MAP = 80-180 mmHg
49
Q

What 2 mechanisms are in operation for autoregulation?

A

1) Myogenic control (stretch receptors)
2) Tubuloglomerular

50
Q

What 2 things does autoregulation adjust in the kidneys to maintain normal GFR?

A

1) Renal blood flow
2) Glomerular surface area

51
Q

Tubuloglomerular mechaism of autoregulation is operates as what kind of feedback?

A

Negative feedback mechanism

52
Q

Increase in GFR from an increase BP does affects Na+ delivery to macula densa how, which increases what?

A
  • Increase Na+ delivery
  • Increased ATP released
53
Q

How does ATP release from Macula densa affect afferent arterioles?

A

ATP will be metabolized to Adenosine in the juxtaglomerular interstitium. Then combines with receptos in the afferent arterioles and causes vasoconstriction

54
Q

When is autoregulation overrode?

A

During periods of extreme stress or blood loss (hemorrage). Sympathetic stimulation will take precedent.

55
Q

What 2 important results occur from the autoregulatory mechanism being overridden by the sympathetic nervous system?

A

1) Activity of kidney temporarily lessend/suspened in favor of shunting blood to other vital organs
2) Lower GFR reduces fluid loss, thus maintaining higher blood volume and BP for other vital functions.

*Renal function basically stops

56
Q

During extreme stress what happens to the afferent and efferent arterioles?

A
  • Intense vasoconstriction resulting in decreased GFR

Renal I Midterm (8 decks)

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