Impulse discharges from the low pressure side varying with the central blood volume.

Abstract

Afferent impulse discharges via the communicating branch between the superior and inferior laryngeal nerves were recorded in the superior laryngeal nerve after cutting all its branches to the larynx. Two types of nerve discharges that varied with the blood volume, and the venous return were observed. One was a repetitive burst of impulses discharging synchronously with the inflow of blood to the heart. The impulses within a burst increased in response to blood transfusion and disappeared after blood loss or occlusion of the inferior caval vein. The impulse discharges apparently emanate from atrial receptors of type B. The other type was a tonic impulse discharge that decreased on an increase of the blood volume and increased when the blood volume was reduced. The corresponding receptors were stimulated also by occlusion of the inferior caval vein (impulses in right and left nerves) and the pulmonary veins (impulses in the left nerve). The discharges on caval occlusion appeared in the right nerve 0.75±0.23 sec (mean, S.D.,n=22) and in the left nerve 0.50±0.13 sec (n=33) before the drop of the aortic pressure. It is assumed that these discharges emanate from receptors in the walls of the central veins.