Acid Base regulation Flashcards Preview

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Flashcards in Acid Base regulation Deck (57):
1

Where does most of the acid come from within the body? What are the lesser sources?

Breakdown of metabolic products, producing CO2

Lesser = breakdown of proteins produces sulfuric/phosphoric acid

2

What are the three acids that are only secreted through the kidneys?

1. Phosphoric acid
2. Sulfuric acid
3. Lactic acid

3

What is the normal pH of the blood?

7.35-7.45

4

What are the two major organs responsible for regulating blood pH? How long does each take to change the acidity of the blood?

Lungs- fast acting
Kidneys - slow acting

5

What is the range of pH of urine? What does this depend on?

4.5- 8, depending on whether the kidney needs to excrete more acid or more base

6

What is acidemia?

Blood pH <7.35

7

What is acidosis?

Disease process or condition that acts to lower pH

8

What is alkalemia?

Blood pH >7.45

9

What is alkalosis?

Any disease process that raises pH

10

What is severe acidosis?

Blood pH <7

11

What is the highest pH that the body can tolerate?

8

12

What part of the diet can contribute to alkalosis? How?

Fruits, since they contain the salts of weak organic acids (Na, and K)

13

What is the immediate source of buffering changes in blood pH?

Body proteins (Hb)

14

If the pH decreases, what is the response by the respiratory system?

Respiratory center of the brain will increase ventilation to blow off CO2, to decrease carbonic acid

15

Respiratory acidosis is caused by what? (Hypoventilation or Hyperventilation?)

Hypoventilation

16

Respiratory alkalosis is caused by what? (Hypoventilation or Hyperventilation?)

Hyperventilation

17

Can metabolic acidosis/alkalosis be eliminated by respiratory compensation?

No, but can adjust

18

If acidosis/alkalosis is nonrespiratory it is called what?

Metabolic

19

How does the kidney compensate for metabolic alkalosis?

Excrete alkaline urine (HCO3)

20

How does the kidney compensate for metabolic acidosis?

Excreting acidic urine, and reabsorb all of the bicarbonate in the filtrate

21

What is a buffer?

A weak acid/base and its conjugate

22

What is the Henderson-Hasselbalch equation?

pH = pka+log(base/acid)

23

What is the equation for the bicarbonate buffer system? Walk through what would happen if [H] were to increase/decreases.

H2CO3 -> H +HCO3

If H increases, rxn shifts left

If H decreases, rxn shifts right

24

A buffer system acts best around what pH?

where pH = pKa

25

What is the buffer system used by the kidneys and intracellular fluid? What is its pKa?

Phosphate buffer system

pKa = 6.8

26

Why are proteins not part of the normal compensatory response to acid-base changes?

The amount of protein does not change in response to changes in the acid/base status of the body

27

Why is Q the main AA involved in the ammonium buffer system?

can be broken down to HCO3 to go the the blood, and NH4 to the tubular lumen

28

Where in the nephron is H+ secreted? (3) What is the mechanism behind this?

Proximal tubule, thick ascending tubule, and early distal tubule

Na/H exchanger

29

What happens to the H+ secreted into the tubular lumen?

Reacts with HCO3 to produce bicarb.

Bicarb then converts to CO2 and H2O, and CO2 is picked up by the blood or converted to bicarb

30

How do we "reabsorb" bicarb from the nephron?

Pump out H, take in H2O that that makes, and react it with water to produce bicarb

31

For every H+ secreted into the tubular lumen, what happens?

a bicarbonate ion enters the blood

32

How do we increase bicarb [c] if there is no more bicarb left in the tubular lumen?

Use carbonic anhydrase to convert CO2 in the blood to bicarb, and pump out H ion into the tubular lumen. Cl is used to follow this.

33

What is the rxn that carbonic anhydrase catalyzes?

CO2 + H2O -> bicarb + H

34

How does the hydrogen phosphate system work in the tubular cells?

Same way as CO2 is excreted, but more inert compound produced (NaH2PO4)

35

What drives the dissociation of bicarb?

Drawing out H ions into the tubular lumen, which can be picked up by bicarb, phosphate, or excreted with Cl

36

What if we have reabsorbed all the bicarbonate and used up all the phosphate buffers that can be excreted but are still acidotic? What is the next system utilized?

The glutamine- NH4+ system can be used for compensating for extreme acidotic condition

37

What is the Q-NH4 system? Where does this take place in the nephron?

Q can be broken down into two bicarbs and two ammonium ions to be secreted into the urine

This is found in the proximal tubule

38

What is the process utilized later in the nephron to have the same effect as the Q-NH4 system?

ammonia is excreted to ensure urine is not too acidic

39

What is secreted in the urine if the body needs to get rid of acid?

H+ and NH4

40

What is secreted in the urine if the body needs to get rid of base?

HCO3

41

How do the kidneys compensate for respiratory alkalosis? (hint, there is less CO2)

Reabsorb less bicarb; increase bicarb excretion

42

What are the axes of the Davenport diagram?

X= pH
Y= [HCO3]

43

What happens to the davenport curve if you have an increase in baseline pCO2 (e.g. in COPD)

Shift up

44

What happens to the davenport curve if you have an decrease in baseline pCO2?

Shifts down

45

Short term changes are reflected how on the Davenport diagram?

Shifts **along** the respiratory curve

46

Long term changes are reflected how on the Davenport diagram?

Shift of the metabolic curve

47

Review that graph and situations!

Review that graph and situations!

48

How do you differentiate between respiratory and metabolic acidosis in the clinic?

If change is due to pCO2, respiratory

If change is due to HCO change, then it is metabolic

49

What is the process of acid/base secretion used by the proximal tubules?

H/Na exchanger

50

What is the process of acid/base secretion used by the collecting ducts?

H+ ATPase

51

What are the two buffers in the urine that can absorb excess H+ from the blood?

Phosphate and ammonium buffers

52

Where does the NH4 buffer come into play (proximal tubule or collecting duct)?

proximal tubule and thick limb

53

What AA is used to generate 2 NH4 and 2 HCO3 for the ammonium buffer system?

Glutamine (Q)

54

Is NH3 permeable to the cell membrane in the nephron? Is NH4?

NH3 is, but NH4 is not. Thus is hold H+ ions in the urine

55

When is the glutamine budder utilized?

Under extreme acidemia

56

What can hydrogen ions combine with (what are the buffers utilized)?

Cl
PO3
HCO3
NH4 (from Q)

57

Glutamine can be broken down into 2x(NH4 + HCO3). Where does each of these molecules go?

NH4 goes into lumen
HCO3 goes into the interstitium.