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(OMS1) CPR Test 2 > Lecture 14: Renal Physiology 2 > Flashcards

Lecture 14: Renal Physiology 2 Flashcards

1
Q

In order, what layers do fluid pass through as it flows out of the glomerulus?

A

Capillary endothelium > glomerular basement membrane > podocyte epithelium

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2
Q

What is the role of the glycocalyx (on the glomerular endothelium)?
What happens when this is damaged?

A

Anionic gel like protein lines the endothelium and repels anions (like proteins)
Hematuria, proteinuria

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3
Q

What is freely filtered by the filtration barrier?

What isn’t?

A

Water, cations small solutes (gluc, aa and electrolytes)

Proteins, cells (like RBCs)

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4
Q

What are the 2 methods of excretion into the filtrate?

A

Filtered at glomerulus or secreted directly into tubules from blood stream

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5
Q

How would you calculate urinary excretion?

How would you calculate tubular reabsorption?

A

UE = amount filtered - amount reabsorbed + amount secreted

Rearrange to solve for amount reabsorbed

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6
Q

What are 2 ways of leaving the kidney?

A

Renal vein > venous return

Ureter > urine

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7
Q

How do you calculate urine excretion rate?

How do you calculate urine flow rate?

A 
X = Ux (V)
V = urine volume/time
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8
Q

What is glomerular filtration rate (GFR)?
What is filtration fraction (FF)?
What is renal blood flow (RBF)?

A
  • rate at filtration at glomerulus
  • amount of fluid that passes through glomerulus to filtrate (usually 20% of RBF)
  • total blood going to glomerulus
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9
Q

How do you calculate GFR?

A

FF = GFR/RBF

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10
Q

What influences GFR?
What influences FF?
How does FF influence oncotic pressure?

A
  • starling force changes
  • RBF and GFR
  • higher FF = more filtered = less fluid more proteins left in capillary = higher plasma colloid osmotic pressure that forces fluid back into capillary
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11
Q

What is the difference between filtered load and filtration fraction?

A

Load: how much filtered in mg/min

FF = GFR/RBF (a ratio)

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12
Q

*How to calculate filtered load?
How to calculate amount reabsorbed?
How to calculate amount excreted?

A

GFR x plasma Na
Filtered load - excreted
V x urine Na

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13
Q

When can you use clearance rate to solve GFR (GFR = Cx)?

A

Substance filtered at glomerulus, not reabsorbed or secreted at the tubules, no broken down by kidney and non-toxic

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14
Q

What is the importance of Inulin and Creatinine when determining GFR?
Which is used clinically? Why?

A
  • Inulin and creatinine meet these conditions, so you can use their Ux, V and Px (aka clearance rate) values to calculate GFR
  • Creatinine because it is produced by skeletal muscle activity and you don’t need to keep infusing it
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15
Q

What are the effects of the SNS on renal function?

A

Vasoconstriction of afferent arteriole
Stimulates renin production at juxtoglomerular cells
Increases activity of Na/K ATPase to increase Na+ resorption

All lead to increase in BP

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16
Q

What SNS receptors will vasoconstrict the arteriole?
What SNS receptors respond to RAAS?
What SNS receptors will increase Na/K ATPase activity and Na+ resoprtion?

A
  • a1 (located at afferent arterioles)
  • B1 (located at kidney)
  • a1 (located at proximal tubule)
17
Q

What forces push fluid out of the glomerular capillary?
What forces push fluid into the glomerular capillary?
How would you calculate the net starling forces occurring at the glomerulus?

A
  • Hgc and Obc (hydrostatic capillary pressure and osmotic bowman’s capsule pressure)
  • Ogc and Hbc (osmotic capillary pressure and hydrostatic bowman’s capsule pressure
  • Net force = (Hgc + Obc) - (Ogc + Hbc)
18
Q

How do you calculate GFR using hydaulic conductivity (Lp), surface area (Sf) and ultrafiltration pressure (Puf) ?

A 
GFR = Kf x Puf
Kf = Lp x Sf
19
Q

What influences the ultrafiltration pressure (Puf?)

A

Hydrostatic pressure of both GC and BC, osmotic pressure of GC
(Puf = Hgc - Hbc - Ogc)

20
Q

What influences Hgc?

A

Renal arterial BP and resistance at afferent and efferent arterioles

21
Q

What is the role of glomerular mesangial cells?

A

Contractile cells that contract glomerular capillaries to decrease surface area (Sf)

22
Q

What happens to hydrostatic pressure as it passes through the renal circulation?

A

Overall declines from arterial to venous side, but needs to be high enough at the glomerulus to filter that much blood

23
Q

Hgc, GFR and RBF

What happens to these if you constrict the afferent arterioles?
What happens to these when you dilate the afferent arterioles?
What happens to these when you constrict the efferent arterioles?
What happens to these when you dilate the efferent arterioles?

A
  • block blood from entering glomerulus (decrease Hgc, GFR and RBF)
  • increase blood flow into glomerulus (increase Hgc, GFR and RBF)
  • block blood from exiting the glomerulus (increase Hgc, GFR, decrease RBF)
  • increase blood leaving the glomerulus (decrase Hgc, GFR, increase RBF_
24
Q

If you want to drop hydrostatic pressure a lot, which one should you constrict?

A

Afferent arteriole

25
Q

What substances are arteriole vasoconstrictors?

A

NE/E
Endothelin
ATP/Adenosine
Angiotensin II (acts mostly on efferents)

26
Q

What substances are arteriole vasodilators?

A 
Prostaglandins
Bradykinin
NO
Dopamine
ANP
ACE Inhibitors
27
Q

What do GFR (filtration) changes do to proximal tubular capillaries (reabsorption)?

A

Directly proportional

Example: increased GFR = more stuff filtered = more stuff you need to reabsorb

28
Q

What does autoregulation of renal blood pressure mean?

A

Stopping drastic changes in RBF and GFR when systemic BP changes so you don’t damage your kidneys (similar to how brain and heart protect their vasculature) > trying to keep BP constant even if systemic BP changes a lot

29
Q

How does local myogenic reflex autoregulate renal vasculature?

A

Resist stretch in the glomerular capillaries when BP is high by constricting the afferent and dilating the efferent arterioles

30
Q

Macula densa senses that Na+ low in the filtrate. What does the kidney want to do and how does it do it? (hint: tubuloglomerular feedback mechanism)

A

since we are low on Na+, kidney wants to keep more Na+. it wants to stop losing Na+ to urine and enhance its reabsorption tactic.

action: Afferent arteriole constricts (TPR goes up) and efferent arteriole dilates (TPR goes down). Since there is less blood at the glomerulus, less things get filtered, so GFR decreases, and less Na+ gets out. To enhance its reabsorption tactic, Jxtg cells will also release more renin. .

31
Q

How does macula densa signaling work?

A

NaCl delivered to macula densa > increase ATP/adenosine signaling > afferent arteriole vasoconstricts via Ca2+ signaling > decrease GFR

32
Q

What is fractional excretion?

How do you calculate this?

A

Percentage of how much of what was filtered actually ended up in the urine.
Fex = amount excreted/amount filtered

(OMS1) CPR Test 2 (26 decks)

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