1. Buffer systems in the body provide an immediate response to fluctuations in pH through chemical buffers like phosphate, protein, and bicarbonate systems. The bicarbonate buffer system predominates in extracellular fluid and its concentration can be regulated by respiratory and renal systems. 2. The respiratory system responds to changes in pH by altering breathing rate - hyperventilating in response to acidosis and hypoventilating in response to alkalosis. This regulates the exhalation of carbon dioxide to bring pH back toward normal. 3. The renal system compensates for acid-base imbalances over 24 hours through retaining or excreting bicarbonate and hydrogen ions as needed. It secretes hydrogen

1. Buffer systems

2. RESPONSES TO:
ACIDOSIS AND ALKALOSIS
Mechanisms which protect the body against
life-threatening changes in hydrogen ion
concentration:
1) Buffering Systems in Body Fluids
2) Respiratory Responses
3) Renal Responses
4) Intracellular Shifts of Ions
2

3. 1) Buffering systems in body fluids provide an
immediate response to fluctuations in pH
1) Phosphate
2) Protein
3) Bicarbonate Buffer System
3

4. Chemical buffers are able to react
immediately (within milliseconds).
Chemical buffers are the first line
of defense for the body for
fluctuations in pH.
4

5. 1) Phosphate buffer system
Na2HPO4 + H+ NaH2PO4 + Na+
Most important in the intracellular system
Phosphate concentrations are higher
intracellularly and within the kidney tubules.
5

6. 2) Protein Buffer System
Behaves as a buffer in both plasma and cells.
Most important intracellular buffer (ICF).
The most plentiful buffer of the body.
Hemoglobin is by far the most important
protein buffer.
6

7. 3) Bicarbonate Buffer System
Predominates in extracellular fluid (ECF)
HCO3
- + added H+ H2CO3
This system is most important because the
concentration of both components can be regulated:
Carbonic acid by the respiratory system
Bicarbonate by the renal system
7

8. 2) Respiratory Responses
Overall compensatory response is:
Hyperventilation in response to increased
CO2 or H+ (low pH).
Hypoventilation in response to decreased
CO2 or H+ (high pH).
8

9. RESPIRATORY CONTROL OF pH
9
pH rises toward normal
rate and depth of breathing increase
CO2 eliminated in lungs
H+ stimulates respiratory center in medulla oblongata
H2CO3 H+ + HCO3
-
H+ acidosis; pH drops
CO2 + H2O H2CO3
cell production of CO2 increases

10. 3) RENAL RESPONSE
The kidney compensates for Acid - Base imbalance
within 24 hours and is responsible for long term
control.
The kidney in response:
To Acidosis
Retains bicarbonate ions and eliminates
hydrogen ions.
To Alkalosis
Eliminates bicarbonate ions and retains
hydrogen ions.
10

11. Mechanism of HCO3
- Reabsorption and
Na+ - H+ Exchange

12. H+ secretion in Distal & Collecting Tubule

13. H+ secretion and excretion couples with addition of
HCO3 to plasma

14. Control of rate of tubular secretion & H+
reabsorption

15. Other Urinary Buffers
 The minimal urine pH is about 4.5
 In order to excrete more H+, the acid must be
buffered in tubular lumen.
 H+ secreted into the tubule combines with HPO4
-2
or NH3.
 HPO4
-2 + H+ H2PO4
-2
 NH3 + H+ NH4
+

16. Buffering of Secreted H+ by Filtered phosphate
(NaHPO4
-) and Generation of “New” HCO3
-
“New” HCO3
-

17. Glutamine is the most abundant free amino
acid that:
1- Help in protein synthesis.
2- regulate acid –base balance in the kidney
by producing ammonium.
During metabolic acidosis, the kidney
becomes the major site for glutamine
extraction and catabolism.

18. Production and Secretion of NH4
+ and HCO3
- by Proximal,
Thick Loop of Henle, and Distal Tubules
“New” HCO3
-
H++NH3

19. 4) Intracellular Shifts of Ions
Hyperkalemia
Is generally associated with acidosis.
Accompanied by a shift of H+ ions into cells and K+
ions out of the cell to maintain electrical neutrality.
Hypokalemia
Is generally associated with reciprocal exchanges
of H+ and K+ in the opposite direction.
Associated with alkalosis.
19

20. ELECTROLYTE SHIFTS
20
cell
H+
K+
Acidosis
Compensatory Response Result
- H+ buffered intracellularly
- Hyperkalemia
H+
K+
cell
Alkalosis
Compensatory Response Result
- Tendency to correct alkalosis
- Hypokalemia

21. Summary of acid base abnormalities