Convergence of stimuli in arterial chemoreceptors.

Abstract

A single chemoreeeptor fibre of the carotid sinus nerve responds both to hypoxia and to hypercapnia/acidity of the arterial blood. These reactions have been well brought out by such recent studies as those of Lahiri1 which he has illustrated in a figure in his paper at this symposium. If reactions to CO2 are presented as a series of CO2 response curves at various intensities of hypoxia, the curves appear as a fan of approximately straight lines which have a steeper slope the more intense the hypoxia. It is when there is some degree of hypoxia that the effects of CO2 become marked in the steady state, as Neil2 has always emphasised, but if the PCO2 arterial blood is changing, the effects of CO2 on discharge are more striking, for adaptation of the response to a sudden change of PCO2 marked, particularly in hyperoxia. Thus if a receptor is discharging at some steady initial level and the PaCO2 is suddenly raised, the discharge immediately rises along a steep transient response curve and then adapts down to lie upon the steady state curve.