The effectiveness of the control of pH in the extracellular fluid of the brain by the respiratory control system

Summary

The “effectiveness” of the respiratory control system as a regulator of the pH in the extracellular fluid of the brain is defined by ΔpH_{ECF op}/ΔpH_{ECF cl} where ΔpH_{ECF op} means the primary or open loop shift and ΔpH_{ECF cl} the final or closed loop shift of brain extracellular fluid pH. The analysis of a steady state model described in a preceding paper (Loeschcke, 1973) allows, in the limits of the suppositions and simplifications, to calculate the effectiveness of the feedback regulator in the cases of increased metabolism, metabolic acidosis-alkalosis and inhalation of CO₂. The effectiveness is diminished if CO₂ production is increased, it drops in metabolic acidosis and rises in metabolic alkalosis and it drops steeply if CO₂ is inhaled. The effectiveness of this control system depends on the “controlling action” of the controlling element (the ventilation) rather than on varying sensitivity of the sensing element. The controlling effect is defined asC′=−d P _CO2/d V _A orC=d pH_ECF/d V _A.