Acid-Base Balance Flashcards
Normal H+ conc is….., pH of arterial b is…..& of venous is…..
pH range which is compatible with life is……(for few hrs)
40 nEq/L (range 45-35)
7.4 (r7.35-7.45)
7.35
6.8-8
Describe effect of changes in H+ conc on body chemistry
- Changes in excitability of nerve and muscle cells, inc H+ causes depression of CNS & vice versa
- Affects enzymatic activity & disturb metabolism
- Influences potassium level
Mention sources of blood H+
- Volatile acids: carbonic acid formed by cellular oxidation
- Non-volatile acids: inorganic (dietary protein break down produce sulphuric & phosphoric acid), organic (resukt from intermediary metabolism)
The 1st line of defence against changes in pH is…….acts within….., its efficiency is……
Chemical buffer system
Seconds
Limited
The 2nd line of defence against changes in pH is…….acts within….., its efficiency is……, its mechanism is….
Respiratory system
Minutes
Moderate
Contril blood CO2 by adjusting pulmonary ventilation
The 3rd line of defence against changes in pH is…….acts within….., its efficiency is……, its mechanism is….
Kidney mechanism
Hrs to days
Highest most powerful
Controlling blood HCO3- & modify H+ secretion and excreting either alkaline or acidic urine
The main buffer system in ECF is……consists of……
Bicarbonate buffer system
H2CO3/NaHCO3
The major buffer system in ICF is……consists of……
Protein buffer system
Proteinate/proteinic acid
Hemoglobin buffer system consists of……its function is……
Haemoglobinate/acid haemoglobin
Buffers H+ generated from CO2 at tissue level
Phosphate buffer system consists of……its function is……
Monohydrogen phostphaye & dihydrogen phosphate
It is the major buffer im kidney and a major buffer in ICF
What does a change in HCO3-/PCO2 ratio indicate?
When it inc, it is due to either fall in PCO2 or a rise in HCO3-, & vice versa.
pK of bicarbonate buffer is….., while that of phosphate buffer is……
6.1
6.8
GR: Bicarbonate buffer is the most effective buffer in ECF
- Although pK=6.1, which is away from blood pH but H2CO3 & HCO3- are abundant in ECF, so this system is rapidly available to resist changes in pH
- The two components of buffer system are regulated the 1st by respiration the 2nd by kidney
Mention factors affecting effectiveness of a buffer
- pK of buffer, the nearer it is to the pH it has preserve the more effective
- Amount of buffer present: the greater amount the more effective
H+ is not secreted in……
Descending loop of Henle & thin ascending loop of Henle
In PCT & LH, ….can be reabsorbed in exchange for H+
K
List sources of CO2 in renal tubules
- Tubular lumen
- Tubular cells
- Plasma
List methods of H+ buffering in tubules
- Buffering with HCO3- to form H2O +CO2
- Phosphate buffers
- Transport excess H+ into urine by tubular ammonia buffer system
List factors affecting H+ secretion in kidney
- PCO2
- K conc
- Carbonic anhydrase
- Aldosterone
List causes of respiratory acidosis
- Respiratory center depression (drugs, injury)
- Paralysis of respiratory muscles
- Pulmonary diseases e.g. obstruction, pneumonia, pulmonary edema
Describe correction of respiratory acidosis
- By chemical blood buffers
- By renal mechanisms
a. Inc in bicarbonate reabsorption causing retention of HCO3- thus ratio HCO3-/CO2 will inc
b. Inc excretion of H+ leading to inc titritable acid excretion
c. Inc ammonium excretion in urine
List causes of respiratory alkalosis
- Fever, anxiety, aspirin poisoning
- Psychic voluntary ventilation
- High altitude (low O2 content stimulates respiration)
Describe correction of respiratory alkalosis
- Chemical blood buffer
- Renal correction
a. Dec reabsorption of HCO3- and is excreted in urine
b. Dec excretion of H+ in urine in the form of titritable acid & ammonium salts
List causes of metabolic acidosis
- Loss of Na+ bicarbonate: severe diarrhea, renal tubular acidosis, CAI
- Excess acid: diabetic ketoacideosis, renal failure (uremic acidosis), severe muscular exercise (lactate), toxins (salicylate & methanol intoxication), excess protein & fati diet (acidifying diets)
Describe correction of metabolic acidosis
Except for uremic acidosis compensation is by renal, respiratory & chemical buffer mechanisms.
Kidney excretes more H+ & reabsorbs more HCO3- so that ratio is restored
In uremic acidosis, compensation in not complete bec respiration can compensate up to 75%
The anion gap value is….. (range…..)
12 mEq/L
8-16 mEq/L
Compare hyperchloremic & normochloremic acidosis with respect cause & anion gap
H: diarrhea, renal tubular acidosis, CAI
N: Ketoacidosis (diabetes & starvation), lactic acidosis, renal failure
List causes of metabolic alkalosis
- Excessive Vomiting (loss of HCl)
- Alkalinizing drugs (NaHCO3, antacids)
- Excess aldosterone secretion
- Potassium deficiency
Describe correction of metabolic alkalosis
- Blood chemical buffer liberate H+
- Respiratory by dec ventiation causes CO2 retention
- Renal compensation dec H+ excretion & inc HCO3 excretion
Normal PCO2 is…..& normal bicarbonate is……
40 (r35-45)
24 (r22-28)
