Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Renal > Acid Base Balance 1 > Flashcards

Acid Base Balance 1 Flashcards

1
Q

What is the normal pH of arterialized blood? How does the concentration of H+ in the blood compare to other ions (Na / K / Cl)?

A

7.4

[H+] is usually about a millionth that of other ion concentrations, only free [H+] contributes to pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the major sources of H+ in the blood?

A
  1. Respiratory acid (not usually a large contributor bc lungs provide effective short term control of pH changes due to respiration)
  2. Metabolic acids: organic (FA’s, lactic acids) and inorganic acids (S-containing AA’s)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does Ka relate to the strength of an acid? What is meant by a “strong” acid?

A
  • Large Ka value = stronger acid

- Strong acids are ones that dissociate more in solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the normal ratio of bicarbonate : carbonic acid in the blood? Why is this?

A

20:1
It’s because the p(Ka) of carbonic acid is less than the ideal pH of the blood, so need more base to up the pH

Don’t know if actually need to know this shit, but Scholz is making a big deal of it so…

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What determines the amount of carbonic acid in the blood?

A

The amount of CO2 dissolved in the plasma

  • Depends on the solubility of CO2 and the pCO2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the normal bicarbonate and carbonic acid ranges in the blood?

A

Bicarbonate: aim for 24, range: 22 - 26

Carbonic acid: around 1.2mmol/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Due to the relationship between carbonic acid concentration and CO2, what equation approximates pH of the blood?

A

pH ~ [bicarbonate] / PCO2

pH is proportional to [HCO3] over the partial pressure of CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is the lung regulation of acid base balance not adequate, causing a need for kidney involvement?

A

The lungs use the bicarbonate buffer to control pH precisely in the short term, but a shift to either the left or the right of the equation leaves the body with a inappropriate levels of bicarbonate, either too much or too little

  • Resp. can control PCO2 well, but not [HCO3]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Other than the bicarbonate buffer, what are some buffer systems in the body?

A

Plasma protein buffers:
Pr + H — HPr

Phosphate buffer
HPO4 + H — H2PO4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the primary intracellular buffers?

A

Proteins

Organic and inorganic phosphates

Haemoglobin (in RBCs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How can acidosis lead to hyperkalaemia?

A
  • High H+ in the blood, cells respond by taking some H+ up

- Have to exchange the H+ for something to maintain electrochemical neutrality, send K+ into the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where are respiratory acids and metabolic acids buffered? In plasma or in cells?

A
  • Respiratory acids: 97% buffered within cells (particularly Hb)
  • Metabolic acids: 43% buffered in plasma with HCO3, 57% in cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the ways in which the kidneys regulate [HCO3]?

A
  1. Reabsorption of filtered HCO3

2. Generating new HCO3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the mechanism by which the kidneys reabsorb filtered HCO3

A
  1. Active secretion of H+ from tubule cells to lumen
  2. Coupled to passive Na reabsorption
  3. Filtered HCO3 reacts with H+ to produce H2O and CO2 (via carbonic anhydrase)
  4. CO2 is freely permeable and enters the cell
  5. Within the cell CO2 – H2CO3 via carbonic anhydrase, which dissociates to H+ & HCO3
  6. The H+ is the source of the active H+ secretion, the HCO3 moves into the peritubular capillaries with Na
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where does most bicarbonate (HCO3) reabsorption occur?

A

In the proximal tubule (90%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How much H+ excretion occurs during HCO3 reabsorption?

A

None.

17
Q

What reaction is catalyzed by carbonic anhydrase?

A

Both:
H2O + CO2 — H2CO3
&
H2CO3 —- H2O + CO2

18
Q

How many mmoles of H+ are produced per day and need excretion by the urinary system?

A

50-100mmoles

  • Need buffers in urine. If that much H was dissolved in 1L urine, would have a pH of 1
19
Q

What are the three most important buffers in the urine?

A
  • dibasic phosphate (HPO4)
  • Uric acid
  • Creatinine
20
Q

Why is the buffer system in the urine called titratable acidity?

A

Because their extent is measured by the amount of NaOH needed to titrate the urine back to a pH of 7.4

21
Q

Describe the phosphate buffer system in the urine (titratable acidity process)

A
  1. CO2 diffuses from blood into the tubular cells, combines with H2O to form H2CO3 via carbonic anhydrase
  2. There is NaHPO4 in the urine, dissociates to Na & HPO4
  3. The H2CO3 dissociates to H+ & HCO3
  4. The Na in the urine and H in the tubular cell are exchanged
  5. The H binds the HPO4 in the urine, gets excreted
  6. The HCO3 from the carbonic acid moves with the Na into the peritubular capillaries
22
Q

Where does the titratable acidity process (phosphate buffer system) occur? Why is it more favourable here?

A
  • In the distal tubule
  • Because the phosphate ions are greatly concentrated here due to the removal of the bulk of the initial filtrate, so it is in high enough concentration to be used as a titratable acid
23
Q

Describe the mechanism by which ammonium excretion is a response to a high acid load in the distal tubule

A
  1. CO2 moves into the tubule cells, forms H2CO3 via CA, dissociates to H+ & HCO3
  2. NH3 is produced by renal tubule cells, moves freely into the tubule lumen
  3. H+ in tubule cells and Na (from NaCl) in urine exchanged
  4. NH3 binds secreted H+, NH4 then binds Cl (from NaCl) so that NH4Cl is neutral & ready for excretion
  5. Na & HCO3 in tubule cells move into peritubular capillaries
24
Q

How does the ammonium excretion mechanism affect the acid base balance in the body?

A
  • Secretes an H+ to lower acidity

- Makes a new bicarbonate to regenerate the buffer system

25
Q

Where does the NH3 in the distal tubule ammonium secretion mechanism come from?

A
  • Produced by the deamination of amino acids (primarily glutamine) by renal glutaminase in the tubule cells
26
Q

How does the ammonium secretion mechanism differ in the proximal tubule?

A

In the proximal tubule there is a NH4 / Na exchanger in the tubule cell membrane, so that NH4 formed within the tubule cells can move into the tubule lumen

Net effect is the same

27
Q

Once ammonium (NH4) is formed in the tubule lumen, what stops it from moving back into the tubule cells?

A

Its positive charge

Not lipophilic

28
Q

How much of the bodies acid secretion does the ammonium secretion mechanism account for?

A

Depends on the severity of the acid load

Renal glutaminase very pH dependent, and when the pH in the cell drops its activity increases greatly. Normally on 30-50mmol H are lost as NH4 per day, but can increase to 250mmol if needed

29
Q

How responsive is the ammonium secretion mechanism?

A

Renal glutaminase is very responsive to pH, but the system as a whole takes 4-5 days to reach maximum efficacy due to the increased requirements of protein synthesis

Renal (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions