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Urinary System > Acid Base Nonsense > Flashcards

Acid Base Nonsense Flashcards

1
Q

What is the normal pH of arterial blood?

A

7.4

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2
Q

What are the two sources of H+?

A

Respiratory Acid

Metabolic Acid

  • inorganic acids such as H2SO4 and phosphoric acids
  • organic acids such as lactic acid and fatty acid
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3
Q

What are the sources of alkali in the body?

A

Oxidation of organic anions such as citrate

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4
Q

What is the role of buffers?

A

To minimise changes in pH when H+ ions are added or removed

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5
Q

What is the ratio of HCO3- to H2CO3 in blood?

A

20:1

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6
Q

What is the concentration of HCO3 in blood?

A

24mmol/l

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7
Q

What is the normal level of pCO2 within the body?

A

40mmHg/5.3pKa

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8
Q

What occurs if there is an increase in H+ (Acidosis)?

A

There is an increase in ventilation and a decrease in CO2

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9
Q

What occurs if there is a decrease in H+ (alkalosis)?

A

There is a decrease in ventilation and an increase in CO2

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10
Q

In the henderson-hasselbalch equation, what is each varient controlled by?

A

HCO3 - renal regulation

Pco2 - respiratory regulation

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11
Q

What occurs if you decrease the concentration of HCO3?

A

pH then decreases and so does pCO2

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12
Q

What can act as intracellular buffers?

A

Proteins, Organic/Inorganic phosphates, Erythrocytes, Haemoglobin

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13
Q

What must occur if H+ ions are buffered by intracellular buffers?

A

They must be accompanies by Cl- or exchanged for K+

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14
Q

What happens to potassium levels in acidosis?

A

Hyperkalaemia

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15
Q

How much of metabolic acid is buffered by plasma?

A

43%

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16
Q

How much of metabolic acid is buffered in cells?

A

57%

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17
Q

How much respiratory acid is buffered within cells ?

A

97%

18
Q

What affects pCO2 ?

A

Respiratory Disorders

19
Q

What affects HCO3?

A

Renal disorders

20
Q

What occurs in respiratory acidosis?

A

There is a decrease in pH bc of an increase in pCO2

21
Q

What causes respiratory acidosis?

A

Acute - barbituates, opiates

Chronic - Bronchitis, Emphysema, Asthma

22
Q

What occurs in respiratory alkalosis?

A

Increase in pH bc of a decrease in CO2

23
Q

What are the causes of respiratory alkalosis?

A

Acute - hyperventilation, aspirin, altitude

Chronic - longterm residence at high altitude

24
Q

What is metabolic acidosis?

A

An decrease in pH due to a decrease in HCO3

pCO2 then decreases to compensate for acidic conditions

25
Q

What causes metabolic acidosis?

A

Increase in H+ production - ketoacidosis, lactic acidosis, failure to excrete normal dietary load of H+, Loss of HCO3 (diarrhoea)

26
Q

What is metabolic alkalosis?

A

Increased pH due to increased HCO3

pCO2 then also increases to compensate for alkalotic conditions

27
Q

What are the causes of metabolic alkalosis?

A

Increase in H+ ion loss - vomiting, Increase in H+ renal loss, Excess administration of HCO3- in those who are renally impaired, massive blood transfusions

28
Q

Describe HCO3- reabsorption

A
  1. Sodium ions are reabsorbed from filtrate in exchange for H+ via an antiport mechanism in the apical membrane
  2. Filtered HCO3- reacts with H+ to form H2CO3 which will combine with carbonic anhydrase to form H2O and CO2
  3. Carbon dioxide enters cell and enters a reaction with H2O (aided by carbonic anhydrase) to form carbonic acid
  4. Carbonic acid dissociates to form a bicarbonate ion and hydrogen ion
  5. H+ ions are secreted and HCO3- pass into peritubular capillaries with Na+
29
Q

What is the min urine pH?

A

4.5-5

30
Q

What is the max urine pH?

A

8

31
Q

What upregulates the Na/H ion antiporter?

A

Angiotensin II

  • promotes Na+ reabsorption and H+ secretion.
32
Q

What is the basis of titratable acidity?

A
  1. NaHPO4 lies within the lumen. One Na+ is exchanged for an H+ ion
  2. Carbon dioxide indirectly forms bicarbonate which enters tubule cells and combines with water to form carbonic acid (aided by carbonic anhydrase)
  3. Carbonic Acid then dissociates to yield H+ and HCO3-
33
Q

What is the function of titratable acidity?

A

To make new Bicarbonate and excrete H+

34
Q

What is the purpose of ammonium excretion?

A

Response to increased acid loads and forms new bicarbonate AND excretes H+

35
Q

What occurs in ammonium excretion?

A
  1. Deamination of amino acids by glutaminase within renal tubule results in NH3 production
  2. NH3 leaves tubule lumen and combines with H+ ions to produce NH4+. NH4+ then combines with CL- to produce NH3Cl- and this is excreted
  3. New H+ions are generated from CO2 in blood
  4. HCO3- passes with Na+ into peritubular capillaries
36
Q

What affect does pH have on renal glutaminase?

A

When intracellular pH decreases (becomes more acidic), renal glutaminase activity increases which increases NH4+ production and excretion

37
Q

What is the relationship between Hydrogen and SOdium in titratable excretion?

A

For every H+ excreted, one Na+ is absorbed

38
Q

What is the relationship between hydrogen, sodium and bicarbonate during HCO3 reabsorption?

A

For every H+ excreted, Na+ conserved, one bicarbonate is reabsorbed

39
Q

if pH = 7.25, [HCO3] = 12mmoles/l, Pco2= 25mmHg, why does this indicate impaired renal function?

A

Damage to nephron means that kidneys are not removing enough acid from the blood stream

Evident that values show metabolic acidosis

40
Q

if pH = 7.45, [HCO3] = 12mmol/l, Pco2 = 20mmHg, why does this indicate that the patient has been living at high altitude?

A

pH is only slightly raised yet HCO3 and CO2 are lower than usual. Lower bicarb and carbon dioxide would suggest metabolic acidosis to compensate for the initial respiratory alkalosis

41
Q

if pH= 7.28, [HCO3]= 36mmol/l, Pco2= 60mmHg, why would the patient be excreting ammonium ions?

A

acute and chronic acid loads enhance ammonia production in the proximal tubule and secretion into the urine

42
Q

if pH=7.5, [HCO3]= 45mmol/l. Pco2= 60mmHg. why would the subject be secreting bicarbonate ions?

A

increased excretion of HCO3− as the filtered load of HCO3− exceeds the ability of the renal tubule to reabsorb it.

Urinary System (15 decks)

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