Lecture 1: Renal Physiology Review Flashcards

1
Q

In which 2 compartments are protein levels the highest?

A

1) ICF compartments
2) Vascular compartments

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2
Q

What is the pressue generated by large molecules (like proteins) in solution that are impermeable to membranes?

A

Oncotic (colloid osmotic) pressure

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3
Q

Which 4 indicators can be used to measure ECF?

A
  • 22Na+
  • 125I-iothalamate
  • Thiosulfate
  • Inulin
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4
Q

How is ICF volume calculated?

A

TBW - ECF = ICF

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5
Q

Why can albumin (125I-albumin) be used to measure plasma volume?

A

Does not cross plasma membranes

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6
Q

How is interstitial fluid volume calculated?

A

ECF - plasma = ISF

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7
Q

ECF osmolality is driven (primarily) by?

Where are the concentrations of Na+ greatest between the vasculature, ICF, and interstitial fluid (rank them)?

A
  1. Na+ and Cl-
  2. [Na+] vasculature > [Na+​] interstital fluid > [Na+​] ICF
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8
Q

ICF osmolality is primarily driven by what ion(s)?

A

K+

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9
Q

ECF osmolality controls ______ volume

A

ECF osmolality controls ICF volume

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10
Q

All solutes that enter or leave the body do so via the?

A

ECF

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11
Q

Hypernatremia is defined as plasma [Na+] >?

A

plasma [Na+​] > 146 mEq/L

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12
Q

Hyponatremia is a defined as plasma [Na+​]

A

plasma [Na+​] < 136 mEq/L

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13
Q

How is filtration rate calculated (equation)?

What are the components of the equation (i.e., Pc, Pi, πc, πi..)?

A

Filtration rate = Kf[(Pc−Pi)−σ(πc−πi)]

  • Pc = hydrostatic pressure within capillary
  • Pi = hydrostatic pressure of interstitial fluid
  • πc = oncotic pressure of plasma
  • πi = oncotic pressure of interstitial fluid
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14
Q

How is anion gap calculated?

A

Anion gap = [Na+] - ([Cl-] + [HCO3-])

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15
Q

When IV 0.9% NaCl (normal saline) is added to ECF what change occurs to osmolality and volume?

A
  • No change in osmolality
  • Only volume of ECF is increased
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16
Q

When IV 3% NaCl (hypertonic) is added to ECF what change occurs to osmolality and volume?

A
  • Osmolality increases and pulls water from ICF into ECF
  • Increased ECF volume and decreased ICF volume = cells shrink
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17
Q

When IV 0.45% NaCl (hypotonic) is added to ECF what change occurs to osmolality and volume?

A
  • Osmolality of ECF decreases and water moves out of ECF into the ICF to equilibrate = cells swell
  • ECF and ICF volumes BOTH increase
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18
Q

What is the stimulus for Angiotensin II in the kidney?

Effects on GFR and RBF?

A
  • ↓ ECF volume = stimulus
  • Causes ↓ in GFR and ↓ RBF
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19
Q

What are the 5 stimuli for Endothelin release in the kidney?

Effect on GFR and RBF?

A
  • ↑ Stretch, Angiotensin II, bradykinin, epinephrine, ↓ ECF volume = stimulus
  • Causes ↓ GFR and ↓ RBF
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20
Q

What are the 2 stimuli for release of Prostaglandins in the kidney?

Effects on GFR and RBF?

A

↓ ECF volume and ↑ shear = stimulus

  • No change/↑ GFR and ↑ RBF
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21
Q

What are the 6 stimuli for NO release in the kidney?

Effects on GFR and RBF?

A
  • Stress, shear stress, ACh, histamine, bradykinin, and ATP = stimulus
  • ↑ GFR and ↑ RBF
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22
Q

What are the 2 stimuli for Bradykinin release in the kidney?

Effect on GFR and RBF?

A
  • Prostaglandins, ↓ ACE = stimuli
  • ↑ GFR and ↑ RBF
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23
Q

What is the stimulus for Natriuretic Peptides (ANP, BNP) in the kidney?

Effect on GFR and RBP?

A
  • ↑ ECF volume = stimulus
  • ↑ GFR and no effect on RBF
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24
Q

Caution should be taken when administering what drug to hypertensive pts, renal stenosis pts, and patients on diuretics?

A

NSAIDs due to interference with PGE2 —> Na+ retention

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25
Q

The afferent and efferent arterioles of the kidney are innervated by what neurons?

A

Sympathetic

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26
Q

Which NT’s are released by sympathetic nerves at the afferent and efferent arterioles in the kidney?

A
  • Norepinephrine
  • Dopamine
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27
Q

With negative Na+ balance which arterioles of the kidney constrict in response to α-adrenergic stimulation and what are the downstream effects?

A
  • Afferent > efferent
  • Afferent vasoconstriction –> reduced hydrostatic pressure in glomerular capillary lumen + decreased glomerular filtration
  • Reduces GFR + filtered load of Na+ to the nephrons + increased systemic BP
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28
Q

What is the effect of sympathetic stimulation of the β1 receptors on juxtaglomerular granular cells?

A

Renin release + RAAS —> Increased BP

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29
Q

Reabsorption of what along the nephron is directly stimulated by α-adrenergic stimulation?

What is the most important segment of kidney influenced by sympathetic nerve activity?

A
  • NaCl reabsorption via Na-K ATPase —> reducing fraction of filtered Na+ that is ultimately excreted
  • Most important segment = proximal tubule
30
Q

Increased renal sympthathetic nerve activity on the kidney is an adaptive response with what ultimate goal?

A

net NaCl excretion and restore normal ECF volume

31
Q

When Na+ balance is altered, the kidneys take several day to respond maximally to these alterations and reach a new steady state.

What changes in volume and plasma [Na+] occur during positive/negative Na+ balance?

A
  • Positive [Na+] balance, the ECF volume expands = no change plasma [Na+]
  • Negative [Na+] balance, the ECF volume contracts = no change plasma [Na+]
32
Q

The combined action of which 2 segments of the nephron reabsorb approximately 92% of the filtered amount of Na+?

A
  • Proximal tubule
  • Loop of Henle
33
Q

Which 2 parts of the nephron make final adjustments in Na+ excretion to maintain a euvolemic state?

A
  • Distal tubule
  • Collecting duct
34
Q

During ECF volume expansion there is increased release of what from the heart and what from the kidney?

A
  • ANP and BNP from the heart —> Increased Na+ excretion
  • Urodilatin by the kidneys –> decreased collecting duct Na+ reabsorption
35
Q

What are the 2 factors which lead to decreased secretion of ADH with ECF volume expansion?

A
  • ↑ Na+ excretion, plasma osmolality begins to fall –> ↓ ADH (posterior pituitary)
  • ↑ levels of natriuretic peptides –> ↓ ADH (posterior pituitary)
36
Q

During ECF volume contraction, volume sensors in both the high- and low-pressure vascular circuits send signals to the kidneys that cause what 3 changes?

A
  1. ↑ renal sympathetic nerve activity
  2. ↑ renin secretion –> ↑ angiotensin II levels and thus ↑ aldosterone secretion by adrenal cortex
  3. Stimulation of ADH secretion by posterior pituitary

*Reduce NaCl and water excretion!

37
Q

What is the effect of ADH on the late portion of the distal tubule and the collecting duct?

A

Enhances water reabsorption and stimulates limited Na+ reabsorption

38
Q

What 3 factors are important in stimulating renin secretion?

A
  1. Perfusion pressure
  2. Sympathetic nerve activity
  3. Delivery of NaCl to the macula densa
39
Q

Renin alone does not have a physiological funtion, how does it act and describe the series of events to follow?

A
  • Functions as proteolytic enzyme and cleaves angiotensinogen (liver)—> angiotensin I
  • Angiotensin Iis cleaved byACEfound on vascular endothelial cells (pulmonary and renal) intoAngiotensin II
40
Q

What are the 2 important functions of ACE?

A
  • Converts angiotensin I —-> angiotensin II
  • Degrades bradkykinin
41
Q

What are the 4 important physiologic functions of Angiotensin II?

A
  1. Stimulation of aldosterone by adrenal cortex
  2. Arteriolar vasoconstriction (↑ BP)
  3. Stimulation of ADH secretion and thirst
  4. Enhancement of NaCl reabsorption by the nephron
42
Q

Aldosterone secretion is stimulated by what 2 things?

A
  1. Angiotensin II
  2. Increased plasma [K+]
43
Q

Aldosterone stimulates the reabsorption of NaCl in which 3 parts of the nephron?

A
  1. Thick ascending limb
  2. Portions of distal tubule
  3. Collecting duct
44
Q

What are the portions of the distal tubule and collecting duct that functionally respond to aldosterone called?

A

Aldosterone sensitive distal nephron (ASDN)

45
Q

Upon its action on the ASDN, aldosterone causes an increase in the abdundance of which channels/transporters for Na+ reabsorption?

A
  • Na-Cl symporter in the cells of distal tubule
  • ENaC channels in apical membrane of principal cells in the late distal tubule and collecting duct
  • Na-K-ATPase pump on basolateral membranes
46
Q

Other than Na+ reabsorption, Aldosterone also has an effect on what 2 other ions?

A
  • Increase in K+ excretion
  • Tubular secretion of H+ thru stimulation of H+-ATPase in the apical membrane of α-intercalated cells
47
Q

How is Na+ reabsorbed in the first half of the proximal tubule vs. the second half?

A
  • First half = Na+ primarily reabsorbed w/ HCO3- + glucose, AA’s, Pi, and lactate
  • Second half = Na+ reabsorbed mainly w/ Cl-
48
Q

Majority of NaCl is filtered in the proximal tubule by which 2 routes?

A
  • 2/3 move across via transcellular path
  • 1/3 moves across via paracellular path
49
Q

Which molecules are reabsorbed in both the descending limb and thick/thin ascending limb of the loop of Henle?

Which channels are necessary for H2O reabsorption?

A
  • Descending = does NOT reabsorb NaCl. But H2O reabsorption occurs exclusively in some portions via AQP1 channels
  • Ascending = impermeable to H2O; but can reabsorb NaCl

*Ca2+ and HCO3- are reabsorbed in loop of Henle

50
Q

What can be reabsorbed in the early distal tubule of the nephron?

A
  • Na+
  • Cl-
  • Ca2+

*Impermeable to H2O

51
Q

Which transporter is found in the early distal tubule for reabsorption of NaCl and how do they ions leave the cell once inside?

A
  • Na+-Cl- symporter (NCC)
  • Na+ leaves cell via Na+-K+-ATPase
  • Cl- diffuses thru Cl- channels
52
Q

Thiazide diuretics inhibit what channel?

A

NCC symporter (Na+-Cl-)

53
Q

Major stimulus for Angiotensin II and where are its sites of action?

What’s its effect?

A
  • ↑ Renin = major stimulus
  • Acts on PT, TAL, DT/CD
  • ↑ NaCl and H2O reabsorption
54
Q

Major stimulus for Aldosterone and where are its sites of action?

What’s its effect?

A
  • ↑ Angiotensin II = major stimulus
  • Acts on TAL and DT/CD
  • ↑ NaCl and H2O reabsorption
55
Q

Major stimulus for ANP, BNP, and urodilatin and where are its sites of action?

What’s its effect?

A
  • ↑ ECF volume = major stimulus
  • Act on the CD
  • ↓ H2O and NaCl reabsorption
56
Q

Major stimulus for sympathetic nerve activity in the nephron in regards to transport?

Where do they have effect?

Effect on transport?

A
  • ↓ ECF volume = major stimulus
  • Act on PT, TAL, DT/CD
  • ↑ NaCl and H2O reabsorption
57
Q

Major stimulus for Dopamine release in the nephron and at which sites does it act?

Effect on transport?

A
  • ↑ ECF volume = major stimulus
  • Acts on PT
  • ↓ H2O and NaCl reabsorption
58
Q

What are the 2 sites within the nephron where ADH can have an effect?

A
  • DT
  • CD
59
Q

What causes Central Diabetes Insipidus?

How does it present?

A
  • ↓ ADH due to either damaged pituitary or hypothalamus
  • Polyuria, nocturia, and, due to the initial elevation in serum sodium and osmolality, polydipsia (very thirsty)
60
Q

What is the dysfunction in Nephrogenic Diabetes insipidus?

How do these patients present?

A
  • Kidneys unable to respond to ADH
  • Pt will have polyuria, nocturia, and polydipsia
  • Plasma [Na+] and osmolality are elevated, and kindeys will excrete large quantities of very dilute urine
61
Q

In SIADH what will the plasma osmolarity and urine osmolarity be like?

A
  • Hyponatremia —> ↓ plasma osmolarity w/ ↑ volume of H2O
  • ↑ urine osmolarity
62
Q

In adrenal insufficiency what occurs to the volume/osmolality of the ECF and ICF?

A
  • Decreased osmolality in both compartments due to loss of Na+
  • ICF volume
  • ECF volume
63
Q

What are 3 stimuli for renin secretion?

A
  1. Sympathetic activation via β1 receptor activation in JG apparatus
  2. ↓ NaCl delivery to the macula densa = NaCl sensor!
  3. Afferent arteriolar vasocontriction
64
Q

Which 5 hormones cause afferent arteriole vasdilation?

A
  • Prostaglandins
  • Bradykinin
  • NO
  • Dopamine
  • ANP
65
Q

In the early proximal tubule Na+ uptake across the apical membrane is primarily coupled with which other molecules?

Which is the main one?

A
  • HCO3- (primary)
  • Glucose + AA’s
  • Pi and lactate
66
Q

In the late proximal tubule, Na+ reabsorption is primarily coupled with what other ion?

A
  • Cl-
  • Primarily via transcellular route
67
Q

Reabsorption of Na+ in the PCT is primarily driven by what?

A

Na+-K+-ATPase

68
Q

In the loop of Henle which part is concentrating and which part is diluting?

A
  • Concentrating during descent, only permeable to H2O, NaCl remains in tubule
  • Diluting during ascent, H2O is impermeable and NaCl is reabsorbed
69
Q

Function of the principle cells and intercalated cells in the late segment of the distal tubule?

A
  • Principal cells = Na+ reabsorption, K+ secretion, H2O reabsorption
  • Intercalated cells = acid base balance
70
Q

Effect of nicotine and alcohol on ADH?

A
  • Nicotine will increase ADH
  • Alcohol will decrease ADH
71
Q

What 4 events/hormones inhibit renin secretion?

A
  • Increased Na+ and Cl- reabsorption across the macula densa
  • Increased AFFERENT arteriolar pressure
  • ADH
  • Angiotensin II via negative feedback
72
Q

What are the effects of Aldosterone on Na+, K+, and H+?

A
  • Increases Na+ reabsorption
  • Increases K+ secretion
  • Increases H+ secretion