Physiological behavior of thoracic cardiovascular receptors

Functional anatomy of canine cardiac nerves

“…IK undertaking a careful ana lysis of the chronotropic, drom otropic and inotropic effect of the thoracic autonom ic efferent nerves as well as the responses elicited by cardiac afferent nerve stim ulation the numerous thoracic nerves were identified, classified and correlated with their histology. These data, correlated w ith reports of efferent sym pathetic nerve function [R andall ei «/., 1972] and afferent nerve activity [Armour, 1973| of each cardiac nerve, was the basis for the present report which is directed to depicting as com pletely as possible the thoracic auto nomic nerves which subserve a cardiovascular function.…”

“…Efferent stim ulation of the innom inate resulted in predom inantly positive inotropism in both atria and ventricles although vagal effects were usually present also. The ventrom edial nerve is known to contain some afferents from the heart, hut aortic receptor afferents predom inate [Armour, 1973]. This nerve on cross-section contained one or more bundles of large myelinated fibers as well as numerous unm yelinated fibers in other bundles.…”

“…Efferent stim ulation elicited positive cardiac inotropism. elicited no efferent responses; it contains numerous afferent« which arise prim arily from the aorta [Armour, 1973], In contrast, the ventrolateral nerve was made up alm ost entirel\ of unm yelinated fibers ( fig. 7B) with a very few small myelinated fibers.…”

Behavior of left ventricular mechanoreceptors with myelinated and nonmyelinated afferent vagal fibers in cats.

“…They had pulse synchronous discharge under basal conditions, increased their discharge with ventricular distention, and behaved generally like the myelinated fibers from which we recorded, although no measurements of conduction velocity were obtained. Finally, some of the left ventricular endings from which Armour (1973) recorded activity may have been subserved by myelinated fibers, although little information is provided regarding the behavior of these endings, and no conduction velocities were determined. Most of his recordings were obtained from close cardiac nerves, making it virtually impossible to determine whether the endings he studied were subserved by vagal or sympathetic afferent fibers.…”

“…Many of the ventricular fibers studied by Coleridge and colleagues (1964) also seemed to be in or near the endocardium based on responses to probing. Some of the fibers from which Armour (1973) recorded also were most easily stimulated by stroking the endocardium.…”