Acid Base Homeo

Question 1

Three primary systems that regulate H concentration

Answer 1

1 chemical acid-base buffer system of body fluids (combine with acid or base to prevent excessive changes in H concentration)
2 respiratory center (removal of CO2 and carbonic acid)
3 kidneys (excrete and adjust H ion conc)

Question 2

H concentration is kept at a low level in the ecf bec

Answer 2

All activities of enzyme system in the body are influenced by H.

Question 3

pH and relationship with H ion

Answer 3

pH is inversely proportional to the H concentration

Low pH High H concentration
High pH Low H concentration

Question 4

pH =

Answer 4

pH = -log [H]

pH = log 1/[H] = -log[H]

Question 5

Any substance that can reversibly bind H

Answer 5

Buffer

Question 6

How are buffers able to minimize H conc

Answer 6

When H conc increases, the reactions goes to the right more H ions binding with buffer to make a weak acid as long as the buffer is available.

When the H concentration decreases, the reaction shifts toward the left and H is released from buffer.

Question 7

Bicarbonate buffer system 2 ingredients

Answer 7

1 weak acid H2CO3

2 bicarbonate salt NaHCO3

Question 8

Carbonic acid is formed by reaction

by the enzyme

Answer 8

CO2 + H2O <=> H2CO3

Carbonic anhydrase

Question 9

Carbonic anhydrase is present in

Answer 9

Walls of lung alveoli

Epithelial cell of renal tubules

Question 10

H2CO3 is a buffer bec it can ionize quickly to form

Answer 10

H2CO3 <=> H + HCO3

Question 11

NaHCO3 is also a buffer in the ECF bec it ionizes quickly to form

Answer 11

NaHCO3 <=> Na + HCO3

Question 12

Bicarbonate buffer system equation

Answer 12

CO2 + H2O <=> H2CO3 <=> H + HCO3 + Na

Weak dissociation of carbonic acid yields few H conc

Question 13

Adding strong acid to the bicarbonate buffer solution is buffered by

yielding greater amounts of H2O and CO2.

Elimination of CO2 from ECF is by

Answer 13

HCO3

respiration (hypervent)

The opposite occurs if a strong base is added. There will be dec CO2 and inc HCO3 that is compensated by inc renal excretion of HCO3.

Question 14

Henderson Hasselbach =

Answer 14

pH = 6.1 + log HCO3/0.03xPCO2

Question 15

Henderson Hasselbach calculates

Answer 15

pH of soln if the molar concentration of HCO3 and PCO2 are known

defines determinants of normal pH regulation and acidbase balance of ECF

Question 16

Increase in HCO3 causes

Inc in PCO2 causes

Answer 16

pH to rise shifting acid base balance toward alkalosis

pH to decrease shifting acid-base balance toward acidosis

Question 17

HCO3 is regulated mainly by

PCO2 is controlled by

Answer 17

Kidneys

Rate of respiration

Question 18

When two components of buffer system are equal, the pH according to the Henderson-Hasselbach is

Answer 18

equal to pK (dissociation constant) 6.1 of bicarbonate buffer system

Question 19

Buffer power is determined by

Answer 19

Amount and

relative concentration of buffer component

Question 20

The buffer system is most effective when

region in titration curve

Answer 20

pH is near the pK

center

Question 21

Most important extracellular buffer

Answer 21

Bicarbonate buffer system

Question 22

Phosphate buffer system is important in tubular fluids and kidneys and ICF bec

Answer 22

1 phosphate becomes greatly concentrated in tubules inc buffering power of phosphate system
2 tubular fluid has low pH than ECF bringing operating range of buffer close to pK 6.8 of system

Question 23

In RBCs hemoglobin is a buffer:

Answer 23

H + Hb <=> HHb

Question 24

60-70% of chemical buffering of body fluids inside the cell is a result of

Answer 24

intracellular protein buffer

but delayed due to slow diffusion of Bicarbonate and H through cell to buffer ECF

Question 25

Whenever there is change in H concentration in ECF, balance of all buffer systems change at same time.

Answer 25

Isohydric Principle Any condition changing the balance of one buffer system changes the balance of others bec the buffer actually buffers one another by shifting H back and forth.

Question 26

Non volatile acids from protein metabolism are so

Answer 26

Bec they are not excreted by lungs not H2CO3

Question 27

Reduction in ECF H concentration causes failure of kidney to

Answer 27

reabsorb filtered HCO3 | inc excretion of HCO3 to raise H conc back to normal

Question 28

Kidneys regulate ECF H conc through 3 mechanims

Answer 28

secretion of H reabsorption of filtered HCO3 production of new HCO3

Question 29

80-90-% bicarb reabsorption and H secretion occurs in H secretion and bicarb reab occur in all parts of the tubules except

Answer 29

PCT thin limbs LOH

Question 30

H is secreted in PCT, thick ascending LOH and early DT by

Answer 30

Na-H counter transport | Secondary active transport

Question 31

H secretion and HCO3 reabsorption:

Answer 31

CO2 diffuses or formed by metabolism in tubular epithelial cell CO2 + H2O by carbonic anhydrase into carbonic acid Then dissociates into H and HCO3 H is secreted from cell into lumen by Na-H exchanger Na moves into cell and H moves out into lumen The HCO3 in the cell moves downhill at the basolateral membrane into interstitial fluid and peritubular capillary Net result: for every H secreted into lumen, a bicarb entes the blood

Question 32

Transport of bicarbonate across basolateral membrane is facilitated by

Answer 32

1 NaHCO3 co transport in PCT | 2 Cl-HCO3 exchange in late segment of PCT abs TAL, CT, CD

Question 33

Each time a H is formed in tubular epithelial cell,

Answer 33

a bicarb is formed and released back into the blood

Question 34

During acidosis excess H is buffered in tubules by

Answer 34

phosphate | ammonia

Question 35

In distal tubule and cd tubular epithelium intercalated cells secretes H by

Answer 35

active transport by H-transporting ATPase

Question 36

In acidosis, excess H supposedly excreted in the tubule when all HCO3 are exhausted is combined with

Answer 36

Phosphate and ammonia buffers to generate new HCO3 helping replenish lost HCO3 or excreted as Na salt NaH2PO4 carrying excess H

Question 37

Ammonia in kidney comes from

Answer 37

glutamine for each molecule of glutamine in PCT two ammonia are secreted in urine and two bicarbonate are reabsorbed into blood

Question 38

In the collecting duct, ammonia buffering

Answer 38

for each ammonia excreted a new HCO3 is generated and added to the blood

Question 39

With chronic acidosis, the dominant mechanism by which acid us eliminated is

Answer 39

excretion of ammonia also most important mechanism of generatinf bicarb in chronic acidosis

Question 40

Inc H secretion and HCO3 reabsorption

Answer 40

``` Inc PCO2 inc H Dec HCO3 Dec extracellular fluid Inc angiotensin II Inc aldosterone Hypokalemia ```

Question 41

Dec H secretion and HCO3 reabsorption

Answer 41

``` Dec PCO2 Dec H and Inc HCO3 Inc ECF Dec Angiotensin II Dec Aldosterone Hyperkalemia ```

Question 42

In metabolic acidosis, the compensations

Answer 42

1 inc ventilation rate dec PCO2 | 2 renal comp by adding HCO3 to ECF

Question 43

In respi alkalosis, primary compensation:

Answer 43

1 reduction in plasma HCO3 by renal excretion

Question 44

In metabolic alkalosis, primary compensation:

Answer 44

1 dec ventilation raising PCO2 | 2 inc renal excretion of HCO3

Question 45

Renal tubular acidosis (Metabolic Acidosis) assoc d/o

Answer 45

1 chronic renal f 2 Addison’s disease dec aldosterone 3 Fanconi

Question 46

Most frequent cause of metab acidosis

Answer 46

Diarrhea bec of large amounts of sodium bicarb excretion in feces

Question 47

Ingestion of acids contribute to formation of metabolic acidosis

Answer 47

Aspirin | Methyl alcohol lambanogz

Question 48

Diuretics except CA inhibitors cause metabolic alkalosis bec

Answer 48

Inc fluid flow in tubule promotes Na reabsorption which is coupled with H sec and inc bicarb reabsorption Also aldosterone excess (Conn’s)

Question 49

Anion gap formula

Answer 49

Anion gap = Na - (Cl + HCO3)

Question 50

Anion gap inc if

Answer 50

unmeasured anions rise (albumin, phosphate, sulfate) unmeasured cations fall (Ca, Mg, K) N= 8-16

Question 51

Metabolic acidosis with Normal Anion Gap 4

Answer 51

diarrhea renal tubular acidosis carbonic anhydrase inhibtors addison’s

Question 52

Metabolic Acidosis with inc anion gap normochloremia

Answer 52

``` DM Lactic acidosis Chronic renal failure Aspirin poisoning Methanol poisoning Ethylene glycol Starvation ```