BUFFER ACTION 



19 



NaHCOg which we have seen take place would lead to a 

 decrease in Ph were it not for the fact that the body pos- 



TT r\r\ 



sesses three methods for restoring the ratio „ \inr\ ? ^^^ 



o 



so keeping the Ph constant. 



1. The respiratory centre is extremely sensitive to the 

 H-ion concentration of the blood supplying it, responding 

 to the shghtest increase by increasing the pulmonary ventila- 

 tion. This reduces the COg in the alveolar air and therefore 

 the CO2 of the blood. 



2. The kidney responds to increased H-ion concentration 



Piasma. 



Corpuscles 



Fig. 2. — ^IMigration of chlorine ions. 



by excreting acid sodium phosphate until the normal 

 reaction is restored. 



3. The blood itself responds by an interaction of ions 

 between plasma and corpuscles. When COg is added to 

 the blood, chlorine ions migrate from the plasma to the 

 corpuscles, thus, as it were, releasing sodium to combine 

 with COg. This transference of chlorine ions is connected 

 with the fact that reduced haemoglobin (reduced in this 

 case in consequence of the addition of CO2) is less acid 

 than oxyhsemoglobin. The migration of chlorine ions from 

 plasma to corpuscles has the effect of increasing the 

 NaHCOg of the plasma by an amount corresponding to 

 the increase in CO,. 



