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physiology > Exam3Lec7AcidBase2 > Flashcards

Exam3Lec7AcidBase2 Flashcards

1
Q

Total acid production=____ + ____

A

Volatile Acid (99.8 %)+Fixed Acid (0.02 %)

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2
Q

What does the davenport diagram show?

A
  • It is a graphical visualization of the HH equation.
  • pH-Bicarbonate Diagram with PCO2 Isobars
  • By changing PP of CO2 and measuring pH and bicarb you can get different points and put them together to get the normal buffer line.
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3
Q

Is the red solid line or the black solid line a more powerful buffer? Why?

A

red line is a more powerful line because for example when the pp changed from 40 to 80, pp change when from 7.4 to 7.2. The black line change more, pH went from 7.4 to 7,15

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4
Q

What makes blood a better buffer and how?

A

Hemoglobin makes blood a better buffer and increases bicarbonate concentration

more hemoglobin in the blood, makes the slope steeper
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5
Q

Which buffer system is more powerful (left vs right graph) and why?

A

The right graph is more powerful because it represents HCO3-/H2CO3 biffer system with hemoglobin.
As seen on the graph and using the HH equation, then change in the pH is less as pp CO2 incr. It keeps the overall ratio of [HCO3-]/[CO2] relatively the same bc as CO2 incr so does HCO3-. Same for decr.

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6
Q

Explain transport of CO2 and buffering by hemoglobin

why when blood has hemoglobin our plasma buffering system is more powerful?

A

Because Most CO2 is transported in the blood as HCO3-

CO2 comes into cell and is converted to H2CO3 when then dissociates into HCO3- and H+. HCO3- can leave and be reabsorb, Hemoglobin can buffer proton.

incr CO2 concentration, incr bicarb concentraiton in plasma,

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7
Q

Regulation of Body pH is achieved by what 3 mechanisms?

A
  1. Chemical Buffering
  2. Respiratory Compensation (lungs)
  3. Renal Compensation (kidney)
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8
Q

ADDITION OF A STRONG ACID

Lets say that there is an addition of HCL to the plasma (final: 12 mM HCl). Explain the First Line of Defense (fast chemical buffering) with the HH equation. How does the pH change?

A

pH went from 7.4-6.06 with the fast chemical buffering

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9
Q

ADDITION OF A STRONG ACID

Explain acidosis and our second line of defense** (fast respiratory component)** with the HH equation. How does the pH change?

A
  1. With regular ventilation: . The increased [CO2] by buffering is removed by alveolar ventilation, so PCO2 is maintained at 40 mmHg (1.2 mM CO2) and pH goes up to 7.1
  2. Acidosis causes incr in ventilation, so PCO2 decr from 40 to 25 (0.75). pH incr to 7.3 which is closer to 7.4
decr in [HCO3-] and [CO2]. decr in [CO2] b/c neural reflex to increase ventilation.
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10
Q

Explain acidosis and our third line of defense (Slow Renal Compensation) with the HH equation. How does the pH change?

A

Here H+ secretion and HCO3- reabsorption is occuring and Over a period of days plasma HCO3- returns to normal. pH comes back to 7.40

Restoration of [HCO3-], Restoration of [CO2]

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11
Q

How can the kidney bring bicarb concentration from 12mmol back to 24 mmol?

A

By H+ secretion and HCO3- reabsorption through renal transporters of HCO3- and H+

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12
Q

What are 3 main mechanisms of H+ secretion and note their location on the nephron.

A
  1. H+ exchanged for Na+ ( HCO3- reabroption)- at the PT
  2. H+ ATPase and H+K+ATPase in DT and CT
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12
Q

Bicarbonate reabsoprtion primary in ____ and does ____ % of acid excretion

A

PT, 0%

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13
Q

How does bicarbonate reabsoprtion occur in the PT and how is there is no acid excretion?

A
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14
Q

Bicarbonate Reabsorption
(Proximal Tubule)
Summary
____ of Na+ and HCO3-
____ secretion of H+
____ tubular pH

A

Net reabsorption of Na+ and HCO3-
No net secretion of H+
No change in tubular pH

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15
Q

What enhances Na+/H+ exchange in the PT and what are the limits of Net reabsorption of Na+ and HCO3- in the PT?

A
  • ATII enhances Na+/H+ exchange
  • Limits: If filtered load of HCO3- exceeds ~40 mM, the reabsorption mechanism becomes saturated.
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16
Q

Review: what are the non-volatile acids (fixed acids) produced by the human body?

A

H+ + HPO42-
H+ + SO42-

17
Q

Explain Titratable acid excretion
Lxn?
Acid excretion %?

A
  • Proton is being actively pumpped into lumen using ATP and binds to fixed acids and the proton is excreted and bicarb is regenerated
  • Primarily in Distal Tubule & CD
  • Accounts for 33 % of Acid Excretion

every time you secrete a prton you generate a new bicarb

18
Q

Explain Ammonium excretion
Lxn?
Acid excretion %?
[H+]?

A
  • H+ is pumped into the lumen and it binds to NH3 (ammonia). This now becomes NH4+ whihc is membrane impermeable so it becomes excreted. Bicarb is regenerated
  • Primarily in Distal Tubule & CD
  • Accounts for 66 % of Acid Excretion
  • [H+] is 1000 X greater in the lumen than the cell

[H+] is 1000 X becuase H+ is accumulating in the lumen and tubular fluid becomes very acidic

19
Q

Name what each slope represents

A
20
Q

respiratory acidosis/alkalosis is due to ____
metabolic cidosis/alkalosis is due to ____

A

respiratory acidosis/alkalosis is due to CO2
metabolic cidosis/alkalosis is due to HCO3-

21
Q

What causes respiratory acidosis?

A

Any impairment of alveolar ventilation.
1) COPD, CHF and other lung diseases.
2) Anesthetics and Drugs

22
Q

What occurs to pH and CO2 in respiratory acidosis?

A

pH decr due to incr CO2

23
Q

Chronic respiratory acidosis has some metabolic compensation. How does this work?

A

Kindey would help by incr concentration os bicarb to incr bicarb reabsorb so pH can incr.

24
Q

What causes respiratory alkalosis?

A

Anything leading to hyperventilation, in excess of that needed to keep pace with body CO2 production, such that arterial PCO2 drops below 35 mmHg.
1) Pain
2) Anxiety or Hysteria.
3) Hypoxia, High Altitude (mentioned skiing many times)

25
Q

What occurs to pH and CO2 in respiratory alkalosis?

A

pH incr bc CO2 decr

26
Q

Chronic respiratory alkalosis has some metabolic compensation. How does this work?

A

It will decr bicarb so you can decr pH more. (ex: after skiing you pee alot to get rid of bicarb)

27
Q

What are 5 causes of metabolic acidosis?

A
  1. Loss of Bicarbonate Ions (e.g. diarrhea, renal dysfunction)
  2. Inability to secrete H+ ions (renal dysfunction)
  3. Ketoacidosis (diabetes, starvation, alcoholism)
  4. Lactic Acidosis
    (strenuous exercise, shock,
    CO, ARDS, etc.)
    Ingested Drugs or Toxicants
    (methanol, ethanol, salicylates,
    ethylene glycol,
    ammonium chloride)
28
Q

What occurs to pH and HCO3 in metabolic acidosis?

A

pH decr because HCO3 decr

29
Q

What are the causes of metabolic alkalosis?

A

1) Too much Intake of Base (antacids, i.v. or ingested bicarbonate)
2) Loss of Acid (vomiting, gastric suction tube, diuretic therapy, steroid therapies).

30
Q

What occurs to pH and HCO3 in metabolic alkalosis?

A

pH incr because HCO3- incr

31
Q

Fill in the blank for Renal and Respiratory Compensatory Responses to Disturbances in Acid-Base Balance

A

Overall concept: compensation is always going in same direction as response bc you want to minimize change in HCO-3/ CO2 ratio

32
Q

What are 3 renal responses to metabolic acidosis

A
  1. Decreased filtered bicarbonate
  2. Increased H+ secretion: coupled to bicarb reabsoprtion and generation of new bicarb
  3. Increased NH3 production (b/c linked to incr H+ secretion)
33
Q

What mediates long-term Renal Compensation for Acidosis?

A

Ammonia (we incr ammonia production to excrete more acid; ammonia is turned into ammonium and then excreted)

34
Q

What are 3 factors that stimulate H+ secretion

A
  1. Acidosis (Metabolic or Respiratory)
  2. Aldosterone
  3. Hypokalemia
35
Q

How does aldosterone and hypokalemia incr H+ secretion?

A

High Aldosterone: Stimulates H+ secretion
And K+ secretion. Thus Aldosterone lowers plasma
K+. (hypokalemia). The end result is that NH3
Is also increased.

Hypokalemaia leads to more acid secretion b/c NH3 production is normally inhibited by K+. So there is less inhibition and more NH3 production and more H+ secretion

36
Q

Anion Gap= ____- ____

A

Plasma [Na+] - ( [Cl-] + [HCO3-] )

37
Q

For metabolic acidosis there are 2 types of anion gap acidosis. What are they and what can they represent clinically?

A
  1. Normal anion gap acidosis: HCO3- decreases and replaced by Cl- shift
    * EX: Diarrhea or simple gain of H+ + Cl-
  2. Increased anion gap acidosis : HCO3- decreases and replaced by other organic anions so no Cl- shift
    * EX: actic acidosis, diabetic ketoacidosis, salicylate poisoning, methanol poisoning

look at annion gaps for diagnosing

38
Q

Acid-base Balance Part II Summary
1. ____ improves buffering capacity of blood
2. Changes in PCO2 cause____
3. Changes in HCO3- cause ____
4. The respiratory compensation for acid-base imbalance is a change in ____
5. The renal compensation for acid-base imbalance is to due to change in ____
6. The anion gap is useful for____

A
  1. Hemoglobin improves buffering capacity of blood.
  2. Changes in PCO2 cause respiratory acidosis/alkalosis.
  3. Changes in HCO3- cause metabolic acidosis/alkalosis.
  4. The respiratory compensation for acid-base imbalance is a change in respiration/ventilation, and is relatively fast (minutes).
  5. The renal compensation for acid-base imbalance is due to change in HCO3- reabsorption and H+ secretion.
  6. The anion gap is useful for differentiating the cause of metabolic acidosis.
39
Q

True or False: Bicarbonate is readily absorbed by the tubule because of its high permeability.

A

False

reabsorbed by CO2 diffusion on lumen side and on capillary side its by Na+ bicarb transporter or HCO3-/Cl- exchanger

40
Q

True or False: A carbonic anhydrase inhibitor decreases renal bicarbonate reabsorption and H+ secretion.

A

True

41
Q

True or False: Hypokalemia leads to reduced renal H+ secretion and acidosis.

A

False

incr renal secretion

physiology (22 decks)

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