Extent of Engagement of Various Cardiovascular Effectors to Alterations of Carotid Sinus Pressure

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Abstract
Reflex adjustments of blood pressure, heart rate, skeletal muscle and renal resistance vessels to changes in intrasinusal pressure were recorded and the respective sinus pressure—reflex response curves plotted. In this way one could evaluate whether the various individual reflex arcs, which together constitute the baroreceptor reflex control of the circulation, display “threshold” response and maximal sensitivities, respectively, at identical sinus pressures.—The curves describing the blood pressure, muscle and renal resistance vessel responses were found to follow identical courses, while the heart rate response curve was displaced to the right of the others. This discrepancy is, however, in all probability a mere consequence of the peculiar neuro‐effector characteristics in the heart. The individual components of the baroreceptor reflex, therefore seem to be recruited simultaneously when the sinus pressure is increased, and there is thus nothing to indicate that afferents from low and high “threshold” baroreceptors, respectively, are preferentially distributed to different neuron pools in the bulbar cardiovascular centres.—A displacement of the response curves to the right was observed whena) non‐pulsating sinus pressures were used instead of pulsating,b) sinus pressures alterations were induced by lowering the pressure from higher levels instead of elevating it,c) arterial PCO2 was increased.