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Flashcards in Renal Test Deck (68):
1

Where is 98% of the Potassium in the body?

Why?

Intracellular

creates charge potential

2

What is normal Potassium concentration?

4 mEq/L

3

An increase in K+ ______ excitability.

Increases

4

Hyperkalemia _______ resting membrane potential, which ______ excitability.

Decreases

Increases

5

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

Na/K ATPas rapidly takes up

6

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

Epinepherine

Insulin

Aldosterone

7

What role do kidneys play in regulation of body Potassium?

Excretion when K+ ECF too high

8

Where is filtered load of Potassium reabsorbed along the nephron?

90% Proximal tubule and Ascending limb

10% Delivered to distal nephron

9

How is Potassium excretion primarily regulated?

By controlling the rate of Secretion

*from capillaries into the collecting tubule

10

Potassium excretion primarily regulated by ______

Na and Water excretion primarily regulated by ________

Secretion

Reabsorption

11

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

Secretion from Interstitium into late Distal Tubule and Collecting Tubule

12

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

Secretion stops

Reabsorption

13

Where does Reabsorption occur in case of Hypokalemia?

Luminal/Basolateral channels?



Distal nephron

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

14

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

(1 luminal, 2 basolateral)

Luminal: Na/K ATPase

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

15

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

How?

Increases

By creating Lumen Negative potential

(pushes K+ back into distal nephron)

16

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

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

Decrease

Increase

*this occurs to maintain charge balance

17

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

True

18

T/F
Respiratory acidosis has little to no effect on Plasma K+

True

19

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

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

20

What 2 things affect the rate of Potassium Secretion?

Plasma potassium

Tubular fluid flow rate

21

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

Increases Na/K ATPase activity in Distal Nephrons

Increase Aldosterone secretion

*Ald has 2 effects

22

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

Na/K ATPase activity

Luminal membrane permeability

23

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

Minimizes tubular fluid concentration

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

24

Extended use of loop diuretics leads to...

Hypokalemia

25

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

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

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

Resorbs water do distal nephron unaffected

??

27

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

Kidney, G-Intestinal, Bone

PTH

28

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

Vitamin D activation

Renal Calcium excretion/reabsorption (distal tubule)

Renal Orthophosphate excretion/reabsorption

(HPO4 -2)

29

What does PTH do to phosphate?

Where?

Mechanism?

Decreases reabsorption (increasing excretion)

Proximal Tubule

Inhibits Na/phosphate co-trnasporter on luminal membrane

30

How does PTH stimulate Calcium reabsorption in the Distal Tubule?

2 things

Ca ATPase

Na/Ca exchanger

basolateral membrane

31

What is a volatile acid?

15-20,000 mmol/day CO2

*oxidative metabolism

32

Why are volatile acids usually of no concern?

Exhaled

33

What is a "Fixed" non-volatile acid?

2 things that create?

50 mmol/day inorganic/organic

Exercise, Diabetes (ketoacidosis)

34

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

Bicarb

CO2 respiration

Renal compensation (H+ excretion, bicarb production)

35

What is the point of maximum buffering capacity?

pKa

36

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

True

37

What converts H2CO3 to water and carbon dioxide?

Carbonic Anhydrase

38

What is the typical value of plasma bicarb?

24 mmol/L

39

What is thy typical value of plasma CO2?

1.2 mmol/L

40

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

20:1

41

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

Acid/Base ratio

CO2/bicarb

42

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

H+ and bicarb (HCO3-)

43

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

Exchanges with Cl-

44

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

True

45

T/F
H+ preferentially binds to de-oxygenated Hb

True

46

What 2 factors principally regulate respiration rate?

CO2 levels

Plasma H+ concentration

47

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

New bicarb generation

H+ excretion

48

More than 99% of filtered bicarb is reabsorbed where?

Proximal tubule

49

The reabsorptive process of bicarb in the Proximal Tubule is _____

Indirect

50

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

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

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

H+ ATPase

52

Where is bicarbonate generated in the nephron?

2 places/processes

Distal Intercalated collecting tubule cells (titratable acids)

Proximal tubule (Glutamine metabolism)

53

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

Urinary buffers

*rate limiting step

54

What is metabolized in the proximal tubule to generate bicarb?

What is co-generated?

Glutamine

Ammonium

55

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

Quick depletion

56

The source of renal NH3 is...

NH4 from Glutamine production

57

How can acid-base status affect NH3 synthesis?

Metabolic acidosis increases Glutamine metabolism

Increases NH4

increases NH3+

**increases bicarb synth

58

What are the 3 primary factors regulating H+ secretion?

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

H/Na antiporter
(luminal, proximal tubule)

H+ ATPase
(luminal, intercalated collecting tubule)

59

Where does Aldosterone affect the regulation of bicarb?

Intercalated collecting tubule cells

60

How does Aldosterone affect the regulation of bicarb?

increases H+ ATPase

which increases H+ secretion

which increases HCO3 reabsorption

61

What are the 4 simple acid base disorders

Metabolic/Respiratory Acidosis/Alkalosis

62

How does the kidney compensate for Respiratory acidosis/alkalosis?

changes bicarb levels

*slow response

63

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

True

64

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

Resorb all filtered bicarb

Generate new bicarb

65

What is the proper acid base homeostatic level?

7.4

66

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?

Hypoventilation

67

What is an Anion Gap?

Means of identifying cause of metabolic acidosis

68

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

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

Change

No change

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