Effects of single vagal stimuli on heart rate and atrioventricular conduction
01 May 1970-American Journal of Physiology (American Physiological Society)-Vol. 218, Iss: 5, pp 1256-1262
About: This article is published in American Journal of Physiology.The article was published on 1970-05-01. It has received 106 citations till now. The article focuses on the topics: Vagal escape & Electrocardiography.
Citations
More filters
01 Jan 1984
TL;DR: When both divisions of the autonomic nervous system are active simultaneously, the sympathetic and vagal effects are usually not additive in a simple, algebraic fashion, but the sympathetic—parasympathetic interactions tend to be highly nonlinear.
Abstract: The various structures in the heart are regulated by both divisions of the autonomic nervous system. The sympathetic division exerts facilitatory effects, whereas the parasympathetic has an inhibitory influence. The central nervous system controls the relative levels of sympathetic and vagal activity, usually in a reciprocal fashion; that is, as sympathetic activity is increased, parasympathetic activity is usually diminished, and vice versa. In certain regions of the heart, such as the nodal tissues, parasympathetic effects tend to predominate over sympathetic influences. In other regions, however, such as the ventricular myocardium, the effects of the sympathetic division are usually much greater than those of the parasympathetic division. When both divisions are active simultaneously, the sympathetic and vagal effects are usually not additive in a simple, algebraic fashion, but the sympathetic—parasympathetic interactions tend to be highly nonlinear.
248 citations
01 Jan 1984
TL;DR: The second edition of Physiology and Pathophysiology of the function of the heart as a vital organ under Heart, multidisciplinary, taking over a year to complete.
Abstract: could go on for several pages. Thus the book edited This book emphasizes the fundamental, functional aspects of cardiology. Within the last thirty years, by Sperelakis IS a potent reminder of the almost for the rift between clinical and investigative cardiology gotten fact that cardiology has twO sites, inextrica has widened, because of the overwhelming devel bly related. opment of new clinical procedures, both diagnostic The book deals with subjects in which Dr. Sper and therapeutic. Almost forgotten is the fact that elakis has pioneered: ultrastructure of heart muscle, we owe most of the clinical advances to theoretical electrophysiology, cardiac contractility, and ion ex and experimental observations. I need not remind change. An extension of these subjects is the chapter the reader of the work of Carrel, who performed the dealing with fundamental topics of the coronary cir first experimental coronary bypass in 1902, or the culation. work of the brothers Curie in 1880, both physicists, This book is indeed a timely reminder of the im who discovered piezoelectricity, the keystone in ech portance of the fundamental aspects of cardiology. ogradiography; of the works of Langley, who intro Emphasis on clinical aspects of cardiology alone will duced the receptors concept; of Ahlquist in 1946, result in a sterile and unproductive future for a field who first differentiated between alpha and beta re that has made such stunning advances during the ceptors; of Fleckenstein, a physiologist who pi last thirty years to the benefit of millions of people."
226 citations
208 citations
TL;DR: The rise in Rj was closely related to the increase in resting tension (contracture) and was more pronounced during a second exposure to hypoxia and were potentiated by application of epinephrine, by increasing extracellular calcium concentration, and by increasing frequency of stimulation.
Abstract: This study was performed to determine whether hypoxia in glucose-free solutions can increase the electrical resistance of intercellular junctions in ventricular muscle. Internal longitudinal resistance (Ri), mechanical tension, and transmembrane action potentials were measured simultaneously in cow ventricular trabeculae. The mean control value of Ri was 265 +/- 38 omegacm (mean +/- SE) at 34 degrees C. After 1 hour of hypoxia in glucose-free Tyrode's solution, it had increased by 300 +/- 41% (n = 11, P less than 0.001). The rise in Ri was closely related to the increase in resting tension (contracture). These effects were more pronounced during a second exposure to hypoxia and were potentiated by application of epinephrine, by increasing extracellular calcium concentration, and by increasing frequency of stimulation. Addition of glucose (50 mM) provided some protection against hypoxia. It is inferred that the increase in Ri is entirely due to the increase in the resistance of intercellular junctions (electrical uncoupling). Intracellular calcium may be responsible for both the contracture and the uncoupling.
178 citations
TL;DR: Evidence is provided in support of a topological theory of the existence of a "singular" point in cardiac oscillators.
Abstract: Spontaneous rhythmic activity in isolated cardiac pacemaker cells can be terminated by a brief, subthreshold, depolarizing or hyperpolarizing perturbation of the proper magnitude applied at a specific point in the pacemaker cycle. Evidence is provided in support of a topological theory of the existence of a "singular" point in cardiac oscillators.
175 citations