Cardiovascular Responses to Hypoxic Stimulation of the Carotid Bodies
TLDR
The findings indicate that hypoxic stimulation of the carotid bodies causes a dichotomous sympathetic response, that is, a reduction of sympathetic discharge to the heart and a simultaneous increase of sympathetic discharged to the peripheral vasculature.Abstract:
The hemodynamic responses to hypoxic stimulation of the carotid bodies were investigated in the dog with controlled respiration. A dual, rotating disc oxygenator system was utilized to perfuse the vascularly isolated carotid region alternately with blood of high or low pO2. Perfusion of the carotid bodies with hypoxic blood caused a large reduction of heart rate. The bradycardia response was reduced, but not abolished, by vagotomy. However, the subsequent administration of hexamethonium completely abolished the response. The contractility of the atrium was reduced by carotid body hypoxia, and varying degrees of heart block were frequently observed. These responses were abolished by vagotomy and considered to be due to efferent vagal activity. Ventricular function curves showed that carotid body hypoxia usually caused a reduction, never an increase, of ventricular contractility. This indicates a reduction of sympathetic discharge to the heart. The reduction in heart rate after vagotomy and the reduction in ventricular contractility were associated with a concomitant increase of total peripheral resistance. These findings indicate that hypoxic stimulation of the carotid bodies causes a dichotomous sympathetic response, that is, a reduction of sympathetic discharge to the heart and a simultaneous increase of sympathetic discharge to the peripheral vasculature. Systemic hypoxia caused an increase of both ventricular contractility and total peripheral resistance. Consequently, the hemodynamic responses to systemic hypoxia cannot be entirely ascribed to a primary chemoreceptor reflex from the carotid bodies. It is suggested that the cardiac sympathetic responses seen in systemic hypoxia are due, at least in part, to direct hypoxic stimulation of the central nervous system.read more
Citations
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OtherDOI
Interactions Between Respiration and Circulation
TL;DR: The sections in this article are: Spontaneous Respiratory Variations in the Cardiovascular System, Respiration, Metabolism, and Cardiac Output, and Effects of Changes in thecardiovascular System on Respiration.
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An analysis of the primary cardiovascular reflex effects of stimulation of the carotid body chemoreceptors in the dog.
M. de Burgh Daly,Mary J. Scott +1 more
TL;DR: The purpose of the present investigation was to discover the mechanisms by which the primary cardiac response was brought about and to make observations on the changes in vascular resistance resulting from stimulation of the carotid bodies.
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Interaction of Cardiovascular Reflexes in Circulatory Control
Francois M. Abboud,M. D. Thames +1 more
TL;DR: The sections in this article are: Determinants of Neurogenic Control, Clinical Implications, and Types of Interactions.
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The cardiovascular responses to stimulation of the carotid body chemoreceptors in the dog
M. de Burgh Daly,Mary J. Scott +1 more
TL;DR: The results obtained both in animals breathing spontaneously and ventilated artificially are described, and some of the mechanisms responsible for the observed cardiovascular responses in the two types of preparation were studied.
References
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Reflexogenic Areas of the Cardiovascular System
TL;DR: Experiments done between 1877 and 1926 showed that a rise of blood pressure in the carotid-cephalic circulation induces bradycardia and a fall of the systemic arterial pressure, while a drop in the vehicle pressure provokes acceleration of the heart rate and a rise in the systemicarterial pressure.
Journal ArticleDOI
Ventricular Function I. Starling's Law of the Heart Studied by Means of Simultaneous Right and Left Ventricular Function Curves in the Dog
Stanley J. Sarnoff,Erik Berglund +1 more
TL;DR: The concept of a family of Starling or ventricular function curves adds a third dimension to the adaptive capacity of the heart as put forth by Frank and Starling.
Journal ArticleDOI
Homeometric autoregulation in the heart.
TL;DR: It was found that changes in coronary flow are not essential to the exhibition of this phenomenon and it has been termed homeometric autoregulation in contradistinction to the Frank-Starling or heterometric type of autoreGulation.
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