Lecture 19, acid bases Flashcards Preview

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Flashcards in Lecture 19, acid bases Deck (39)
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1
Q

Bicarbonate buffer system uses what acid/bases?

A
  • H2CO3
  • NaHCO3
  • use of carbonic annhydrase
2
Q

Where can extra HCO3 be excreted from the body?

A

Kidneys

3
Q

What is the net result of the combination of CO2 and H2O?

A
  • increased levels of CO2 have the potential to decrease the pH of the blood.
4
Q

What is the overall effect of lowering the CO2 blood concentration?

A
  • decreased blood CO2 leads to decreased respiratory rate as there the blood pH will be more alkolitic.
  • Therefore is [CO2] blood is decreased the CO2 blow-off will be decreased
5
Q

The major function of the bicarbonate buffer system is what?

A

-control the levels of bicarb and [H]

6
Q

What organs help control the bicarbonate buffer system?

A
  • kidneys (bicarbonate concentration)

- lungs (control the pCO2)

7
Q

Metabolic acidosis disorder is characteristic of what?

A
  • decreased HCO3
8
Q

Respiratory acidosis occurs how and where?

A

-from the lungs with increased levels of pCO2

9
Q

Where does the phosphate buffer system have a major role?

A

-the renal tubular fluid and intracellular fluids

10
Q

Why is the phosphate buffer system important in the kidney tubular fluids?

A
  • higher concentration in the tubules

- the lower pH of the tubular fluids allows for a better operating environment for the buffer system

11
Q

What is the overall net reaction result of the phosphate buffer system?

A

-strong acid is replaced by additional amounts of weak acid and a salt. Resulting in minimal pH change

12
Q

What three ways can the kidneys regulate the extracellular H ion?

A
  • reabsorb filtered bicarbonate ion
  • secrete H ion
  • produce new bicarbonate ions, that would be later reabsorbed
13
Q

How is bicaronate reabsored into the renal insterstitial fluid and ultimately into the blood stream?

A
  • NzHCO3 combines with H ion, to form H2CO3 and is broken down into CO2 and H2O
  • CO2 and H2O is passively absorbed across the membrane, carbonic annhydrase converts the reactants into H2CO3 and breaks down into HCO3 and H ion.
  • forming a cyclical pattern to absorb HCO3 and the H ion can move out of the cell via the Na-H exchanger to produce more carbonic acid in the tubular lumen
14
Q

Where in the nephron does H ion secretion and HCO3 reabsorption occur?

A
  • H ion secretion occurs as secondary active transport except in the descending/ascending thin limbs of henle loop
  • active H ion begins in the late distal tubule in the intercalated cells
  • 80-90% of bicarbonate reabsorption occurs in proximal tubule
15
Q

What process occurs in metabolic acidosis in the kidneys?

A

-regulation to correct the decreased pH, by reabsorbing bicarbonate and secreting new bicarbonate ion into the blood tissue.

16
Q

What happens in metabolic alkalosis in the kidneys?

A

-bicarbonate ions are quickly removed from the extracellular fluid, via renal excretion

17
Q

What is the 2-step process of H ion secretion by the intercalated cells?

A
  • dissolved CO2 in intercalated cells combine with water and form carbonic acid
  • carbonic acid dissociates into bicarbonate, becomes rapidly reabosorbed into blood, and H ion is secreted, by H-ATPase into tubular lumen.
18
Q

What is the best way to describe the incomplete titration?

A

-There is not a one-to-one amount of ions being absorbed an secreted

19
Q

What is the minimun amount of pH that the kidneys are able to achieve?

A

4.5

20
Q

It is important to allow large amounts of H ion to be excreted, why?

A

the amount of nonvolatile acid from metabolism would lead to 2667 L of urine a day, if the H ion remained in free solution

21
Q

How are excess H ions eliminated?

A
  • as bicarbonate ion is formed the H ion is secreted into the lumen by Na-H antiporter.
  • H ion binds with phosphate or ammonia to be excreted in urine
  • bicarbonate ion is absorbed into the blood as a “new” ion
22
Q

The phosphate buffer system does what?

A

Increases the pH of the blood.

  • removes H ion from the blood to help form phosphate components, that produce NEW bicarbonate ion that can be secreted into the blood.
  • -loss of blood [H] and increase of blood [HCO3]
23
Q

How can the kidneys correct for alkalosis?

A

-failure to reabsorb the filtered bicarbonate ion which will lead to decreased blood pH

24
Q

What process occurs with increased levels of CO2?

A

-respiratory acidosis

25
Q

What occurs with decreased levels of bicarbonate ions?

A

Metabolic acidosis

26
Q

What is the primary compensating response for respiratory acidosis?

A

-Increase the plasma concentration of Bicarbonate, initially via the kidney.

27
Q

Metabolic acidosis is compensated by what function?

A
  • the lungs increase ventilation

- the kidneys can also begin to form new bicarbonate ion to extracellular

28
Q

When does respiratory alkalosis occur? And what process begins to compensate for it?

A
  • decrease in [CO2]
  • caused by hyperventilation
  • -reduce plasma HCO3 by increased secretion into tubular lumen
29
Q

Metabolic alkalosis occurs with what and is compensated how?

A
  • increased plasma [HCO3]

- -compensated by decreasing ventilation and increasing bicarbonate ion secretion into the tubular lumen

30
Q

What are two buffer systems in the body, and what else can function as a buffer?

A
  • bicarbonate
  • phosphate
  • proteins act as buffers
31
Q

What buffer system is the most important buffering system in the renal tubular fluid?

A

-phosphate buffer system as it is closer to the optimal operating pH.

32
Q

Compounds that dissociate incompletely into H ions and conjugate base are members of what compounds?

A
  • Weak acids, incompletely dissociate

- Strong acids completely dissociate

33
Q

The bicarbonate buffer system consists of a bicarbonate buffer salt and what other component?

A

-weak acid

34
Q

Primary active H secretion uses H ATPase and occurs in what part of the renal tubules?

A

late distal tubules with intercalated cells

35
Q

Most bicarbonate reabsorption occurs in what part of the renal tubule?

A
  • proximal tubule
36
Q

What occurs with a decrease in bicarbonate ion and results in the decrease in the ratio of bicarbonate ion to carbon dioxide in the extracellular fluid?

A
  • Metabolic Acidosis

- -as the bicarbonate ion level is being decreased

37
Q

Respiratory alkalosis due to a decrease in CO2 caused by hyperventilation is compensated for by what mechanism?

A
  • renal excretion of bicarbonate ion
38
Q

What is the effect of Glutamine if it is absorbed into the tubular cells?

A
  • glutamine degrades into 2 ammonium ion and 2 bicarbonate ion.
  • new bicarbonate is reabsorbed
  • ammonium secreted by Na anti porter
  • ultimately buffers the H ion concentration
39
Q

What does “new bicarbonate ion” refer to?

A

-production of excess bicarbonate in the tubular cells, as H ion is forced to combine with phosphate or ammonia in the lumen