Acid Base regulation Flashcards Preview

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Flashcards in Acid Base regulation Deck (57)
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1
Q

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

A

Breakdown of metabolic products, producing CO2

Lesser = breakdown of proteins produces sulfuric/phosphoric acid

2
Q

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

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

What is the normal pH of the blood?

A

7.35-7.45

4
Q

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

A

Lungs- fast acting

Kidneys - slow acting

5
Q

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

A

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

6
Q

What is acidemia?

A

Blood pH <7.35

7
Q

What is acidosis?

A

Disease process or condition that acts to lower pH

8
Q

What is alkalemia?

A

Blood pH >7.45

9
Q

What is alkalosis?

A

Any disease process that raises pH

10
Q

What is severe acidosis?

A

Blood pH <7

11
Q

What is the highest pH that the body can tolerate?

A

8

12
Q

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

A

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

13
Q

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

A

Body proteins (Hb)

14
Q

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

A

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

15
Q

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

A

Hypoventilation

16
Q

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

A

Hyperventilation

17
Q

Can metabolic acidosis/alkalosis be eliminated by respiratory compensation?

A

No, but can adjust

18
Q

If acidosis/alkalosis is nonrespiratory it is called what?

A

Metabolic

19
Q

How does the kidney compensate for metabolic alkalosis?

A

Excrete alkaline urine (HCO3)

20
Q

How does the kidney compensate for metabolic acidosis?

A

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

21
Q

What is a buffer?

A

A weak acid/base and its conjugate

22
Q

What is the Henderson-Hasselbalch equation?

A

pH = pka+log(base/acid)

23
Q

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

A

H2CO3 -> H +HCO3

If H increases, rxn shifts left

If H decreases, rxn shifts right

24
Q

A buffer system acts best around what pH?

A

where pH = pKa

25
Q

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

A

Phosphate buffer system

pKa = 6.8

26
Q

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

A

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

27
Q

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

A

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

28
Q

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

A

Proximal tubule, thick ascending tubule, and early distal tubule

Na/H exchanger

29
Q

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

A

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
Q

How do we “reabsorb” bicarb from the nephron?

A

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

31
Q

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

A

a bicarbonate ion enters the blood

32
Q

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

A

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
Q

What is the rxn that carbonic anhydrase catalyzes?

A

CO2 + H2O -> bicarb + H

34
Q

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

A

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

35
Q

What drives the dissociation of bicarb?

A

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

36
Q

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?

A

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

37
Q

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

A

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
Q

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

A

ammonia is excreted to ensure urine is not too acidic

39
Q

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

A

H+ and NH4

40
Q

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

A

HCO3

41
Q

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

A

Reabsorb less bicarb; increase bicarb excretion

42
Q

What are the axes of the Davenport diagram?

A
X= pH
Y= [HCO3]
43
Q

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

A

Shift up

44
Q

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

A

Shifts down

45
Q

Short term changes are reflected how on the Davenport diagram?

A

Shifts along the respiratory curve

46
Q

Long term changes are reflected how on the Davenport diagram?

A

Shift of the metabolic curve

47
Q

Review that graph and situations!

A

Review that graph and situations!

48
Q

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

A

If change is due to pCO2, respiratory

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

49
Q

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

A

H/Na exchanger

50
Q

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

A

H+ ATPase

51
Q

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

A

Phosphate and ammonium buffers

52
Q

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

A

proximal tubule and thick limb

53
Q

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

A

Glutamine (Q)

54
Q

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

A

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

55
Q

When is the glutamine budder utilized?

A

Under extreme acidemia

56
Q

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

A

Cl
PO3
HCO3
NH4 (from Q)

57
Q

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

A

NH4 goes into lumen

HCO3 goes into the interstitium.