ABSTRACT
A hypothesis is advanced of the heart rate variability being subjected to beat-to-beat regulation of cardiac cycle duration in order to ensure the resonance interaction between respiratory and own fluctuation of the arterial system volume for minimization of power expenses of cardiorespiratory system. Myogenic, parasympathetic and sympathetic machanisms of heart rate variability are described.
Subject(s)
Heart Rate/physiology , Heart/physiology , Models, Cardiovascular , Myocardial Contraction/physiology , Animals , Cats , Heart/innervationABSTRACT
The spectrogram of heart rate in denervated (vagotomy + propranolol) and artificially ventilated cats always contains the true respiratory peak and 1-3 resonance ones pacing at intervals equivalent to frequency of breathing. Hypothermic decrease of heart rate periodically draws the splitting of respiratory peaks and generation of supplementary rate-dependent peaks reflecting the interference of heart and breathing rhythms. The functional base for detection of mentioned peaks is myogenic reaction of sino-atrial node to its extension by fluctuations of venous inflow.
Subject(s)
Cardiovascular Physiological Phenomena , Sinoatrial Node/physiology , Animals , Cats , Electrocardiography , Fourier Analysis , Heart Rate , Periodicity , Respiration , VagotomyABSTRACT
Denervation of the heart (bilateral vagotomy and propranolol) in artificially ventilated cats didn't remove respiratory peaks on the spectrogram of heart rate, while burst stimulation of vagus nerve increased or decreased them several times by synchronization of the heart and vagus rhythms, which in its turn was observed under the bradycardia only. At the same time, the desynchronization of rhythms provoked severe sinus arrhythmia which had a distinct periodic character. Under these conditions, there were high non-respiratory peaks appearing at the spectrogram of the heart rate that indicated existence of two vagus chronotropic effects: a well known tonic one and special intracycle synchronizing effect correcting duration of every cardiac cycle.
Subject(s)
Heart Rate/physiology , Heart/innervation , Vagus Nerve/physiology , Animals , Anti-Arrhythmia Agents/pharmacology , Autonomic Denervation , Cats , Electrocardiography , Heart/drug effects , Heart Rate/drug effects , Propranolol/pharmacology , Vagus Nerve/drug effects , Vagus Nerve/surgeryABSTRACT
In acute experiments on cats, stimulation of the caudal cardiac nerve inhibited tonic and synchronizing components of the vagal chronotropic effects and suppressed arrhythmogenic effect of vagal stimulation. By contrast, stimulation of ansa subclavia potentiated the effects of vagal stimulation. A novel model of vagosympathetic interactions in the heart of mammals is proposed.
