The normal pH of the blood is maintained the narrow range of 7.35-7..pdf

The normal pH of the blood is maintained the narrow range of 7.35-7.45 that is slightly alkaline.
Any change in the normal value can cause marked alterations in the chemical reactions of the
cell.
The body has developed three mechanisms of defence to regulate or maintenance of blood pH or
acid-base balance.
1. Blood buffers
2. Respiratory mechanism.
3. Renal mechanism.
1. Blood buffers : Buffers are present both in the plasma and in the RBC\'s. The buffer cannot
remove H+ ion from the body, it temporarily acts as a shock absorbent to reduce the free H+
ions.
The blood consists of 3 buffer systems.
A. Bicarbonate buffer system : Sodium bicarbonate and carbonic acid (NaHCO3 - H2CO3) is the
most predominant buffer system of the extracellular fluid and plasma. At blood pH 7.4, the ratio
of carbonic acid is 20:1. Thus the bicarbonate concentration is much higher than carbonic acid in
the blood. This is referred to as alkali reserve and is responsible for the active buffering of h+
ions, generated by the body. The plasma bicarbonate [HCO3-] concentration is around 22-26
mmol/l. Carbonic acid is the solution of CO2 in water.
B. Phosphate buffer system: Sodium dihydrogen phosphate and disodium hydrogen phosphate
(NaH2PO4 - Na2HPO4) constitute the phosphate buffer. It is of less importance in plasma due to
its low concentration with a pk of 6.8, close to blood pH 7.4, the phosphate buffer would have
been more effective, had it been present in high concentration. It is estimated that the ratio of
base to acid fort phosphate buffer is 4, compared to 20 for bicarbonate buffer.
C. Protein buffer system : The plasma proteins and hemoglobin together constitute the protein
buffer system of blood. The buffering capacity of proteins is dependent on the Pk of ionizable
groups of amino acids. The imidazole group of histidine (Pk = 6.7) is the most effective
contributor of protein buffers. The plasma proteins account for about 2% of the total buffering
capacity of the plasma.Hemoglobin of RBC is also an important buffer. It mainly buffers the
fixed acid, besides being involved in the transport of gases (O2 and CO2).
2. Respiratory mechanism : Lungs are actually the most effective organs for rapid pH adjustment
or maintaining acid-base balance. About one-half of the H+ ions drained by the cells to the
extracellular fluids combine with HCO3- to form H2CO3, which disassociates into H2O and
CO2. The CO2 thus formed is subsequently eliminated by the lungs. So the elimination of one
molecule of CO2 means the removal of one H+ ion.
The rate of respiration is controlled by a respiratory center, located in the medulla of the brain,
highly sensitive to changes in the pH of blood. Any decrease in blood pH causes hyperventilation
to blow off CO2, there by reducing the H2CO3 concentration, simultaneously the H+ ions are
eliminated as H2O.
An increase in blood P (P - partial pressure) CO2 increases pulmonary ventilation. Pulmonary
ventilation is also increased with slight incr.

1. The normal pH of the blood is maintained the narrow range of 7.35-7.45 that is slightly alkaline.
Any change in the normal value can cause marked alterations in the chemical reactions of the
cell.
The body has developed three mechanisms of defence to regulate or maintenance of blood pH or
acid-base balance.
1. Blood buffers
2. Respiratory mechanism.
3. Renal mechanism.
1. Blood buffers : Buffers are present both in the plasma and in the RBC\'s. The buffer cannot
remove H+ ion from the body, it temporarily acts as a shock absorbent to reduce the free H+
ions.
The blood consists of 3 buffer systems.
A. Bicarbonate buffer system : Sodium bicarbonate and carbonic acid (NaHCO3 - H2CO3) is the
most predominant buffer system of the extracellular fluid and plasma. At blood pH 7.4, the ratio
of carbonic acid is 20:1. Thus the bicarbonate concentration is much higher than carbonic acid in
the blood. This is referred to as alkali reserve and is responsible for the active buffering of h+
ions, generated by the body. The plasma bicarbonate [HCO3-] concentration is around 22-26
mmol/l. Carbonic acid is the solution of CO2 in water.
B. Phosphate buffer system: Sodium dihydrogen phosphate and disodium hydrogen phosphate
(NaH2PO4 - Na2HPO4) constitute the phosphate buffer. It is of less importance in plasma due to
its low concentration with a pk of 6.8, close to blood pH 7.4, the phosphate buffer would have
been more effective, had it been present in high concentration. It is estimated that the ratio of
base to acid fort phosphate buffer is 4, compared to 20 for bicarbonate buffer.
C. Protein buffer system : The plasma proteins and hemoglobin together constitute the protein
buffer system of blood. The buffering capacity of proteins is dependent on the Pk of ionizable
groups of amino acids. The imidazole group of histidine (Pk = 6.7) is the most effective
contributor of protein buffers. The plasma proteins account for about 2% of the total buffering
capacity of the plasma.Hemoglobin of RBC is also an important buffer. It mainly buffers the
fixed acid, besides being involved in the transport of gases (O2 and CO2).
2. Respiratory mechanism : Lungs are actually the most effective organs for rapid pH adjustment
or maintaining acid-base balance. About one-half of the H+ ions drained by the cells to the
extracellular fluids combine with HCO3- to form H2CO3, which disassociates into H2O and
CO2. The CO2 thus formed is subsequently eliminated by the lungs. So the elimination of one
molecule of CO2 means the removal of one H+ ion.
The rate of respiration is controlled by a respiratory center, located in the medulla of the brain,

2. highly sensitive to changes in the pH of blood. Any decrease in blood pH causes hyperventilation
to blow off CO2, there by reducing the H2CO3 concentration, simultaneously the H+ ions are
eliminated as H2O.
An increase in blood P (P - partial pressure) CO2 increases pulmonary ventilation. Pulmonary
ventilation is also increased with slight increase in H+ ion concentration in blood. On the other
hand, the decrease in blood PCO2 and H+ ion concentration results decrease in pulmonary
ventilation. In such conditions, slow respiration takes place where CO2 is retained in blood until
the removal of PCO2 and pH are restored. Respiratory control of blood pH is rapid but only a
short-term regulatory process.
Hemoglobin of erythrocytes is also important in the respiratory regulation of pH or acid-base
balance. At the tissue level hemoglobin binds to H+ ions and helps to transport CO2 as HCO3-
with a minimum change in pH. In the lungs, as hemoglobin combines with O2, H+ ions are
removed which combine with HCO3- to form H2CO3. The latter dissociates to release CO2 to
be exhaled.

Solution

The normal pH of the blood is maintained the narrow range of 7.35-7.45 that is slightly alkaline.
Any change in the normal value can cause marked alterations in the chemical reactions of the
cell.
The body has developed three mechanisms of defence to regulate or maintenance of blood pH or
acid-base balance.
1. Blood buffers
2. Respiratory mechanism.
3. Renal mechanism.
1. Blood buffers : Buffers are present both in the plasma and in the RBC\'s. The buffer cannot
remove H+ ion from the body, it temporarily acts as a shock absorbent to reduce the free H+
ions.
The blood consists of 3 buffer systems.
A. Bicarbonate buffer system : Sodium bicarbonate and carbonic acid (NaHCO3 - H2CO3) is the
most predominant buffer system of the extracellular fluid and plasma. At blood pH 7.4, the ratio
of carbonic acid is 20:1. Thus the bicarbonate concentration is much higher than carbonic acid in
the blood. This is referred to as alkali reserve and is responsible for the active buffering of h+
ions, generated by the body. The plasma bicarbonate [HCO3-] concentration is around 22-26
mmol/l. Carbonic acid is the solution of CO2 in water.
B. Phosphate buffer system: Sodium dihydrogen phosphate and disodium hydrogen phosphate

3. (NaH2PO4 - Na2HPO4) constitute the phosphate buffer. It is of less importance in plasma due to
its low concentration with a pk of 6.8, close to blood pH 7.4, the phosphate buffer would have
been more effective, had it been present in high concentration. It is estimated that the ratio of
base to acid fort phosphate buffer is 4, compared to 20 for bicarbonate buffer.
C. Protein buffer system : The plasma proteins and hemoglobin together constitute the protein
buffer system of blood. The buffering capacity of proteins is dependent on the Pk of ionizable
groups of amino acids. The imidazole group of histidine (Pk = 6.7) is the most effective
contributor of protein buffers. The plasma proteins account for about 2% of the total buffering
capacity of the plasma.Hemoglobin of RBC is also an important buffer. It mainly buffers the
fixed acid, besides being involved in the transport of gases (O2 and CO2).
2. Respiratory mechanism : Lungs are actually the most effective organs for rapid pH adjustment
or maintaining acid-base balance. About one-half of the H+ ions drained by the cells to the
extracellular fluids combine with HCO3- to form H2CO3, which disassociates into H2O and
CO2. The CO2 thus formed is subsequently eliminated by the lungs. So the elimination of one
molecule of CO2 means the removal of one H+ ion.
The rate of respiration is controlled by a respiratory center, located in the medulla of the brain,
highly sensitive to changes in the pH of blood. Any decrease in blood pH causes hyperventilation
to blow off CO2, there by reducing the H2CO3 concentration, simultaneously the H+ ions are
eliminated as H2O.
An increase in blood P (P - partial pressure) CO2 increases pulmonary ventilation. Pulmonary
ventilation is also increased with slight increase in H+ ion concentration in blood. On the other
hand, the decrease in blood PCO2 and H+ ion concentration results decrease in pulmonary
ventilation. In such conditions, slow respiration takes place where CO2 is retained in blood until
the removal of PCO2 and pH are restored. Respiratory control of blood pH is rapid but only a
short-term regulatory process.
Hemoglobin of erythrocytes is also important in the respiratory regulation of pH or acid-base
balance. At the tissue level hemoglobin binds to H+ ions and helps to transport CO2 as HCO3-
with a minimum change in pH. In the lungs, as hemoglobin combines with O2, H+ ions are
removed which combine with HCO3- to form H2CO3. The latter dissociates to release CO2 to
be exhaled.