Abstract
Many theories have been proposed on the genesis of respiratory sinus arrhythmia (R.S.A.).
The authors have examined a model of the arrhythmia in which haemodynamic disturbance upon a closed loop pressure regulator is assumed to be one of the most important cause under the clinical status.
At first, a model of the blood pressure regulator was constructed and examined deliberately. As the result, it has been revealed that the system has double controlling mechanism, which composes a blood pressure setting loop controlling parametrically the arterial resistance as well as the vagal efferent tone and a pressure regulating loop performing equivalently a negative feedback due to the vagal control of the sino-atrial node.
Then, being forced by an assumed blood pressure disturbance due to respiration, this pressure regulating system was tested by transient as well as frequency responses. The data obtained in men and the model have shown good agreement each other.
Finally, manipulating the arterial resistance and/or the central vagal tone, the we have studied the parametric controllability of the model, and obtained quite interesting results. For instance, according to the increase of the vagal tone, the average heart rate becomes slower, and the R. S. A. becomes more distinguished. These facts may well explain the clinical features in men with hypertonus of the vagus, and seem to tell us the plausibility of this model.
