Acid Base Balance

Question 1

Plasma HCO3 us how much more concentrated then plasma H+

Answer 1

600,000 times (H+ bound to Hb)

Question 2

How is the relationship between CO2, HCO3 and H+ expressed

Answer 2

CO2 + H20 <—-> H+ + HCO3
Shifts according to law of mass action

Question 3

Increase CO2 shifts the equation which direction

Answer 3

To right creating one H and one HCO3

Question 4

Adding H causes equation to shift to what direction

Answer 4

Right
HCO3 acts as buffer resulting in
Increase CO2 + increased H20 <— increased H+ + decreased HCO3

Question 5

How does ventilation compensate for pH disturbances

Answer 5

Peripheral and central chemoreceptors sense changes in plasma PCO2 and or H+ and signal to respiratory CC to adjust ventilation

Question 6

What can correct disturbances in acid-base balance as well as cause them

Answer 6

Ventilation

Question 7

Acidosis causes what kind of ventilation

Answer 7

Hypoventilation - right shift
Decrease plasma CO2

Question 8

Alkaline state causes what type of ventilation

Answer 8

Hyperventilation- left shift
Increase CO2

Question 9

What is direct mechanism of kidneys to handle pH disturbances

Answer 9

Altering rates of excretion or reabsorption of H+
- if alkalosis reabsorb H+
- if acidosis secrete H+ for excretion

Question 10

How do kidneys indirectly handle pH disturbances

Answer 10

Changing rate at which HCO3 buffer is reabsorbed or excreted
- if acidosis buffer excess H+
- is alkaline decrease buffers

Question 11

During acidosis what do kidneys generally do

Answer 11

Excess H+ is buffered by ammonia within tubule cells or enter lumen and buffered by phosphate

Question 12

Is not filtered, enters tubule via secretion only

Answer 12

H+

Question 13

Secretes H+ and reabsorb HCO3

Answer 13

Proximal tubule

Question 14

First mechanism of secretion of H and reabsorption of HCO3

Answer 14

1. Na-H exchanger secretes H
2. H in filtrate combines with filtered HCO3 to form CO2
3. H+ is secreted again to repeat
4. HCO3 is reabsorbed with Na

Question 15

Secondary mechanism of H+ secretion and HCO3 reabsorption

Answer 15

1. Glutamine is metabolized to ammonium and HCO3 2. NH4 is secreted and excreted with H+

Question 16

What controls acid excretion

Answer 16

Distal nephron, initial portion of collecting duct plays role in fine regulation of acid-base balance

Question 17

when do type A intercalated cells in collecting duct function

Answer 17

during acidosis

Question 18

when do type B intercalated cells in collecting duct function

Answer 18

during alkalosis

Question 19

what do type A cells do

Answer 19

function to increase H+ secretion and HCO3 reabsorption
- usually accompanied by increase in K+ reabsorption (can cause hyperkalemia)

Question 20

what do type B cells do

Answer 20

function to increase H+ reabsorption and HCO3 secretion (excreted so less buffer)
- usually accompanied by increased K+ secretion (may cause hypokalemia)

Question 21

what transports H+ on intercalated cells

Answer 21

H+ trasnporters and H-K ATPase

Question 22

what trasnports HCO3 on intercalated cells

Answer 22

HCO3/Cl exchanger

Question 23

what are the differences between transporters on type a and type b

Answer 23

Type A has H+ trasnporters on apical and HCO3 on basolateral
Type B has the opposite

Question 24

what is the range buffers function in

Answer 24

7.38-7.42

Question 25

what are acid-base disturbances classified by

Answer 25

direction of pH change (acidosis or alkolosis) and by the underlying cause (respiratory or metabolic)

Question 26

by the time an acid-base disturbance causes a change in plasma pH what has occurred

Answer 26

body’s buffers are ineffective leaving respiratory and renal compensation to alleviate change

Question 27

4 types of acid/base disturbances

Answer 27

1. respiratory acidosis
2. respiratory alkalosis
3. metabolic acidosis
4. metabolic alkalosis

Question 28

what must respiratory induced changes in pH be resolved by

Answer 28

renal mechanisms (excrete H+, reabsorb HCO3)

Question 29

respiratory acidosis

Answer 29

occurs when alveolar hypoventilation results in CO2 retention and elevated plasma CO2

Question 30

what are possible causes of respiratory acidosis

Answer 30

pulmonary fibrosis, asthma attack, drugs, emphysema, muscular dystrophy

Question 31

respiratory alkalosis

Answer 31

much less common, result of hyperventilation in absence of increased metabolic CO2 production

Question 32

causes of respiratory alkalosis

Answer 32

excessive artificial respiration, anxiety induced hyperventilation

Question 33

what will raise plasma CO2 levels

Answer 33

rebreathing exhaled CO2

Question 34

what does renal system do to compensate for respiratory alkalosis

Answer 34

HCO3 excretion and H+ reabsorption

Question 35

metabolic acidosis

Answer 35

occurs when dietary and/or metabolic input of H+ exceeds H+ excretion
- lactic acid, or ketoacidosis
- can also occur from excessive HCO3 loss (diarrhea)

Question 36

How is metabolic acidosis resolved

Answer 36

rarely seen, resolved by respiratory (increased ventilation) and slow renal compensation (HCO3 reabsorbed, H+ excreted)

Question 37

metabolic alkalosis

Answer 37

excessive vomiting of acidic stomach contents or excessive ingestion of bicarbonate containing antacids

Question 38

what is metabolic alkalosis resolved by

Answer 38

rapidly resolved by decrease in ventilation but can cause hypoxia
renal: HCO3 excreted, H+ reabsorbed