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Flashcards in Renal Test Deck (68)
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1
Q

Where is 98% of the Potassium in the body?

Why?

A

Intracellular

creates charge potential

2
Q

What is normal Potassium concentration?

A

4 mEq/L

3
Q

An increase in K+ ______ excitability.

A

Increases

4
Q

Hyperkalemia _______ resting membrane potential, which ______ excitability.

A

Decreases

Increases

5
Q

What happens to Potassium immediately after ingestion in the GI tract?

A

Na/K ATPas rapidly takes up

6
Q

What 3 hormonal factors are involved in the GI uptake of Potassium?

A

Epinepherine

Insulin

Aldosterone

7
Q

What role do kidneys play in regulation of body Potassium?

A

Excretion when K+ ECF too high

8
Q

Where is filtered load of Potassium reabsorbed along the nephron?

A

90% Proximal tubule and Ascending limb

10% Delivered to distal nephron

9
Q

How is Potassium excretion primarily regulated?

A

By controlling the rate of Secretion

*from capillaries into the collecting tubule

10
Q

Potassium excretion primarily regulated by ______

Na and Water excretion primarily regulated by ________

A

Secretion

Reabsorption

11
Q

How is it that a greater % of potassium is excreted than delivered to the distal nephron?

A

Secretion from Interstitium into late Distal Tubule and Collecting Tubule

12
Q

What are 2 ways the Distal Nephron can compensate for Hypokalemia?

A

Secretion stops

Reabsorption

13
Q

Where does Reabsorption occur in case of Hypokalemia?

Luminal/Basolateral channels?

A

Distal nephron

Luminal: via K+/H+ antiporter
Basolateral: K+ selective

14
Q

In normal Potassium Secretion/Reabsorption, what channels are crossed Luminally and Basolaterally

(1 luminal, 2 basolateral)

A

Luminal: Na/K ATPase

Basolateral: K+ channels and K+/Cl- cotransporters

15
Q

How does an increase in Distal Na+ reabsorption affect Potassium secretion?

How?

A

Increases

By creating Lumen Negative potential

(pushes K+ back into distal nephron)

16
Q

A decrease in ECF H+ (alkalosis) will _____ plasma K+

An increase in ECF H+ (acidosis) will _______ plasma K+

A

Decrease

Increase

*this occurs to maintain charge balance

17
Q

T/F

Inorganic acids have a much greater effect on K+ than organic acids

A

True

18
Q

T/F

Respiratory acidosis has little to no effect on Plasma K+

A

True

19
Q

Does increase in ECF K+ concentration affect acid base status?

A

No?? It appears K is cleared in the kidneys through Secretion

20
Q

What 2 things affect the rate of Potassium Secretion?

A

Plasma potassium

Tubular fluid flow rate

21
Q

An increase in ECF (plasma) K+ concentration will increase Secretion/Excretion in what 2 ways?

A

Increases Na/K ATPase activity in Distal Nephrons

Increase Aldosterone secretion

*Ald has 2 effects

22
Q

How does Aldosterone secretion increase K+ excretion (by secretion)?
2 things

A

Na/K ATPase activity

Luminal membrane permeability

23
Q

In what 2 ways does an increase in tubular fluid flow increase K+ secretion?

A

Minimizes tubular fluid concentration

Increases Na+ reabsorption (which increases Na/K ATPase, increasing intracellular K+)

24
Q

Extended use of loop diuretics leads to…

A

Hypokalemia

25
Q

In what 2 ways does the use of loop diuretics increase K+ excretion?
(leading to hypokalemia)

A

Decreases K reabsorption in thick ascending limb

Increases secretion
(by increasing tubular fluid flow and increasing distal Na absorption)

*and Na reabsorption drives K excretion by increasing Na/K ATPase and increases intracellular K

26
Q

Why doesn’t ADH increase K excretion even though it increases tubular fluid flow?

A

Resorbs water do distal nephron unaffected

??

27
Q

Name 3 organs and 1 hormone that affect plasma Calcium levels.

A

Kidney, G-Intestinal, Bone

PTH

28
Q

What are the 3 functions of the kidney in maintaining Calcium levels?

A

Vitamin D activation

Renal Calcium excretion/reabsorption (distal tubule)

Renal Orthophosphate excretion/reabsorption

(HPO4 -2)

29
Q

What does PTH do to phosphate?

Where?

Mechanism?

A

Decreases reabsorption (increasing excretion)

Proximal Tubule

Inhibits Na/phosphate co-trnasporter on luminal membrane

30
Q

How does PTH stimulate Calcium reabsorption in the Distal Tubule?

2 things

A

Ca ATPase

Na/Ca exchanger

basolateral membrane

31
Q

What is a volatile acid?

A

15-20,000 mmol/day CO2

*oxidative metabolism

32
Q

Why are volatile acids usually of no concern?

A

Exhaled

33
Q

What is a “Fixed” non-volatile acid?

2 things that create?

A

50 mmol/day inorganic/organic

Exercise, Diabetes (ketoacidosis)

34
Q

Name 3 ways the body prevents major shifts in pH when there is constant generation of metabolic acids.

A

Bicarb

CO2 respiration

Renal compensation (H+ excretion, bicarb production)

35
Q

What is the point of maximum buffering capacity?

A

pKa

36
Q

T/F

Bicarb has dual control. The lungs regulate CO2. Kidneys regulate plasma concentration of bicarb.

A

True

37
Q

What converts H2CO3 to water and carbon dioxide?

A

Carbonic Anhydrase

38
Q

What is the typical value of plasma bicarb?

A

24 mmol/L

39
Q

What is thy typical value of plasma CO2?

A

1.2 mmol/L

40
Q

What ratio in the Henderson Hasselbach equation will result in a pH of 7.4?

A

20:1

41
Q

The Henderson-Hasselbalch equation helps predict pH by evaluating what?

A

Acid/Base ratio

CO2/bicarb

42
Q

When CO2 diffuses into the RBC, it is converted to…

A

H+ and bicarb (HCO3-)

43
Q

How does bicarb diffuse out of the lungs (after its trasformation from CO2)?

A

Exchanges with Cl-

44
Q

T/F

The H+ left over in the RBC is buffered by de-oxygenated Hb.

A

True

45
Q

T/F

H+ preferentially binds to de-oxygenated Hb

A

True

46
Q

What 2 factors principally regulate respiration rate?

A

CO2 levels

Plasma H+ concentration

47
Q

What is the contribution of the Kidneys in the extreme case of HCl?
2 things

A

New bicarb generation

H+ excretion

48
Q

More than 99% of filtered bicarb is reabsorbed where?

A

Proximal tubule

49
Q

The reabsorptive process of bicarb in the Proximal Tubule is _____

A

Indirect

50
Q

What is the mechanism of the Indirect bicarb reabsorption that occurs in the Proximal tubule

A

Carbonic Anhydrase forms bicarb Intracellularly, exports H+ to lumen, where bicarb + H+ > water and CO2

IC bicarb exits through basolateral membrane to ECF

*this is 1:1

51
Q

What is the rate-limiting step in the reabsorption of bicarb in the Proximal tubule?

A

H+ ATPase

52
Q

Where is bicarbonate generated in the nephron?

2 places/processes

A

Distal Intercalated collecting tubule cells (titratable acids)

Proximal tubule (Glutamine metabolism)

53
Q

Generation of new bicarb in distal collecting tubule from titratable acids is dependent on the availability of what?

A

Urinary buffers

*rate limiting step

54
Q

What is metabolized in the proximal tubule to generate bicarb?

What is co-generated?

A

Glutamine

Ammonium

55
Q

Why is it essential to have additional tubular buffers (like titratable acid and NH3) other than bicarb?

A

Quick depletion

56
Q

The source of renal NH3 is…

A

NH4 from Glutamine production

57
Q

How can acid-base status affect NH3 synthesis?

A

Metabolic acidosis increases Glutamine metabolism

Increases NH4

increases NH3+

**increases bicarb synth

58
Q

What are the 3 primary factors regulating H+ secretion?

A

Intracellular generation of H+
(water + CO2 via carbonic anhydrase = bicarb + H+)

H/Na antiporter
(luminal, proximal tubule)

H+ ATPase
(luminal, intercalated collecting tubule)

59
Q

Where does Aldosterone affect the regulation of bicarb?

A

Intercalated collecting tubule cells

60
Q

How does Aldosterone affect the regulation of bicarb?

A

increases H+ ATPase

which increases H+ secretion

which increases HCO3 reabsorption

61
Q

What are the 4 simple acid base disorders

A

Metabolic/Respiratory Acidosis/Alkalosis

62
Q

How does the kidney compensate for Respiratory acidosis/alkalosis?

A

changes bicarb levels

*slow response

63
Q

T/F

A change in respiration rate can adjust CO2 levels in cases of Metabolic acidosis/alkalosis

A

True

64
Q

The renal response for a change in pH due to Metabolic disturbances is what?
2 things

A

Resorb all filtered bicarb

Generate new bicarb

65
Q

What is the proper acid base homeostatic level?

A

7.4

66
Q

To compensate for metabolic acidosis, the kidney resorbs and synthesized new bicarb. If pCO2 is low so there’s no H+ secretion, how does the body compensate?

A

Hypoventilation

67
Q

What is an Anion Gap?

A

Means of identifying cause of metabolic acidosis

68
Q

If acidosis is from an organic acid, there is a _____ in gap,

If acidosis is from an inorganic acid, there is _____ in gap

A

Change

No change

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