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Renal Physiology > Part Tres--Electrolyte Balance & Acid/Base Buffer > Flashcards

Part Tres--Electrolyte Balance & Acid/Base Buffer Flashcards

1
Q

___% of total body K+ is intracellular (recall the role of the Na+-K+-ATPase)……Normal plasma [K+] = __ mEq/L:

A

98%…4 mEq/L

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2
Q

What can high [K+] do to resting membrane potential and therefore excitability of the cell?

A

high [K+] = lower resting membrane potential = increased excitability

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3
Q

How do we NOT DIE after eating a banana? (2 ways :))

A
  1. RAPID uptake of K+ into the cells (aldosterone, insulin, eli) 2.Slower renal excretion
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4
Q

‘Obligatory’ reabsorption of approx 90% of the filtered load of K+ in the ________ and the ___________.

A

proximal tubule….thick ascending limb

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5
Q

How is the physiologic regulation of renal K+ excretion primarily achieved?

A

By SECRETING into the LATE distal and collecting tubules (OPPOSITE mechanism from Salt and Water)

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6
Q

How do I find FL (filtered load)?

A

GFR x Amount of Substance in body

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7
Q

Since K+ is secreted late in the game what are the three transporters used? Also, what is driving the charge difference?

A
  1. Na+/K+ pump (BL membrane) 2.K+ channels (L membrane) 3. K+/Cl- cotransporters (L membrane)….Na+ reabsorption at this stage is promoting a negative environment (thus promoting K+ secretion)
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8
Q

What do we do when we have K+ depletion? (name some transporters for me)

A
  1. Energy dependent K+/H+ antiporter (L membrane) 2.K+ selective channels (BL membrane)
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9
Q

What does a hypertonic extracellular environment result in K+ levels in the blood?

A

HyperKalemia

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10
Q

What does cell lysis do to plasma levels of K+?

A

HyperKalemia (exercise-induced muscle breakdown)

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11
Q

What is the relationship between ECF [H+] and Plasma [K+]?

A

Parallel…increase in ECF [H+] = increase in plasma [K+]…vis versa

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12
Q

Metabolic acidosis due to ________ (HCl, H2SO4) increases plasma K+ to a much greater extent than a similar acidosis produced by __________ (lactic acid, keto acids)

A

inorganic acids….vs…..organic acids

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13
Q

How does respiratory acidosis/alkylosis affect plasma [K+]?

A

little to no effect :)

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14
Q

What are the two ways the body works to secrete a high [K+] ECF?

A

Increase Na+/K+ action on the distal nephron cells 2.increase aldosterone secretion (also increases Na+/K+ action AND increases luminal K+ permeability

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15
Q

What does increased tubular flow do to K+ secretion?

A

increases secretion (1.c/o low tubular fluid [K+] 2.more Na+ reabsorption and more Na+/K+ activity)

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16
Q

What can loop diuretics do to plasma [K+]?

A

can cause HypoKalemia (1.less reabsorption 2.more secretion (Na+/K+ pumps goin crazy!)

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17
Q

What are the three ways the body combats hypoCalcemia?? how does the kidney connect to the G.I. tract here?

A

1.Kidney (more to come) 2.G.I. absorption (renal Vit-D activation!!) 3.bone resorption

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18
Q

Which part of the kidney does PTH target? What are the 2 outcomes? Which membrane?

A

PTH acts on the distal tubule…1) Ca2+ ATPase (BL) 2)Na+-Ca2+ exchanger(BL)

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19
Q

How is the problem of hyperPhosphatemia solved during bone resorption? WHERE does this happen?? Which transporter is involved???

A

PTH inhibits Renal HPO42- reabsorption….PROXIMAL TUBULE….the Na+/HPO42- cotransporter on the L membrane is BLOCKED! thus we’ll pee it on out

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20
Q

H+ balance: note that concentrations are expressed in _____ Eq “Normal” pH range: ____ - ____ Survival limits: ____ - ____.

A

7.37 - 7.42…….6.80 - 8.00

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21
Q

What are the two sources for H+ accumulation? What is the release for both?

A

1.Volatile- oxidative metabolism…2. Fixed-AA metabolism

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22
Q

What are the two main ways fixed metabolism causes a build up of acid?

A

1.exercise (lactic acid) 2. DM

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23
Q

How do we get rid of volatile acid?

A

respiration

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24
Q

Which is more prevalent volatile or fixed acid?

A

Volitile is 5,000x more prevalent in the body

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25
Q

What are the three lines of defense against fixed acid accumulation in the body?

A

1.Physiochemical Buffering (H2PO4, HCO3) 2.Respiratory compensation 3.Renal compensation

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26
Q

What does the pK represent?

A

the point of greatest buffering capasity

27
Q

Do our buffer systems work intra or extracellularly?

A

BOTH!

28
Q

Which buffer system is most important? WHY!?

A

bicarb!! cause it’s regulated by the lungs and the kidneys

29
Q

Why doesn’t H2CO3 last very long in the body?

A

Carbonic Anhydrase is very active and converts h2co3 to h2o and co2 very quickly!

30
Q

What is the pK for hco3? why is this relevant?

A

6.1..for the HH eq

31
Q

What is the HH eq for evaluating the bicarb buffer system?

A

pH = 6.1 + log ([24mmol/L hco3])/([1.2 mmol/L co2])===a pH of 7.4

32
Q

What is the MAGIC RATIO for maintaining pH balance in our bodies??

A

20 base : 1 acid (in our eq 24:1.2)

33
Q

Where is co2 converted to H+ and HCO3? What happens to the H+? What happens to the HCO3?

A

in the RBC…the H+ attaches to Hemoglobin…the HCO3 diffuses out via the CHLORIDE SHIFT!

34
Q

What is the Chloride shift? Is this the same in the lungs as in the body?

A

when HCO3 diffuses out of the RBC with an exchange of a Cl-…no they are opposite in the lungs and the body tissue (so in lungs we are picking up HCO3)

35
Q

What is the relationship between plasma [H+]/pCO2 and alveolar ventilation?

A

increase in plasma [H+] and or arterial pCO2/ = increase in ventilation

36
Q

What are the 4 steps to fix pH after infusion of a 12mmol/L HCl I.V.?!?!

A

1.Physicochemical Buffering 2.Respiration to eliminate the increased CO2 made 3.MORE respiration to keep eliminating CO2 (gets us CLOSE to 20b : 1a) 4.RENAL compensation

37
Q

How do the kidneys contribute to fix the pH of our 12mmol/L HCl infusion? (2 ways)

A
  1. make new HCO3 (get it back to 24mEq/L) 2. Excrete the excess H+
38
Q

More than ___% of filtered HCO3- is reabsorbed in the ________.

A

99%….PROXIMAL tubule

39
Q

Reabsorptive process ‘______’ since HCO3- transport proteins not present on the luminal membrane…SO how is it done??

A

‘indirect’….by taking in CO2 and H2O, then using Carbonic Anhydrase to make HCO3 (H+ then peed out)

40
Q

Which two cell types make HCO3?

A

Proximal Tubule Cells & RBCs

41
Q

During the WACK reabsorption of HCO3 process…..H+ secreted into the lumen, combines with ______ HCO3- forming CO2 and H2O.

A

filtered

42
Q

For every __ mEq of filtered HCO3- converted, __ mEq is added to the ECF – “indirect” reabsorption.

A

1 mEq… 1 mEq

43
Q

What two things regulate HCO3 reabsorption?

A
  1. arterial blood pCO2 2.Na+ reabsorption
44
Q

Where does the renal generation of NEW bicarb happen?

A

distal nephron

45
Q

Generation of NEW HCO3- dependent on the availability of _______ to accept secreted H+. What’s a possible downside to this?

A

urinary buffers (HPO42-)..these are limited (filtered load relatively low)

46
Q

HCO3- can also be generated from ________ metabolism in the proximal tubule….Then: Co-generated ________ ion secreted into the tubular lumen.

A

glutamine…..ammonium

47
Q

What happens to the ammonium ion in the NEW bicarb story?

A

it gets reabsorbed in the thick ascending limb

48
Q

Interstitial NH4/NH3 diffuses across ______ cells into the lumen and interacts with secreted H+.

A

intercalated

49
Q

Metabolic _______ increases glutamine metabolism and thus HCO3 synthesis/NH3 availability.

A

acidosis

50
Q

HCO3 synthesis also regulated by ________.

A

Aldosterone

51
Q

OVERVIEW: what three important processes is aldosterone involved in?

A

HCO3 reabsorption, NaCl reabsorption, K+ secretion/excretion

52
Q

Acidemia: blood pH < ____

A

7.35

53
Q

Alkalemia: blood pH > ____

A

7.45

54
Q

What causes the shift in pH during a Respiratory acid/base disturbance?

A

changes in plasma pCO2

55
Q

What causes the pH shift during metabolic acid/base disturbances?

A

changes in plasma HCO3

56
Q

What is an example of each of the four acid/base disturbances?

A

Respiratory acidosis: hypoventilation……Respiratory alkalosis: hyperventilation……Metabolic acidosis: diabetes mellitus……Metabolic alkalosis: chronic vomiting

57
Q

Renal compensation for a pH change due to a primary respiratory change in _____.

A

pCO2

58
Q

Respiratory disturbances involve relatively _____ renal compensatory responses.

A

slow

59
Q

What do I look for during Metabolic Acidosis? Which system compensates for this situation?

A

Is the HCO3- < 24 mEq/L?????…the respiratory sys will compensate!

60
Q

What do I look for during Respiratory acidosis? Which system compensates for this situation?

A

Is the pCO2 > 40mmHg??????….the renal system compensates!

61
Q

What do we use the anion gap to find? Whats the normal range?

A

finds the underlying cause of the metabolic acidosis…Anion gap = [Na+] - ([Cl-] + [HCO3-])….8-16 mEq/L

62
Q

With diabetic ketoacidosis or lactic acidosis, what happens to the anion gap?

A

INCREASES

63
Q

With HCl-induced acidosis & diarrhea, what happens with anion gap?

A

NOTHING :) (just decreased HCO3)

Renal Physiology (5 decks)

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