THE FUNCTIONAL ANALYSIS OF A SYMPATHETIC GANGLION OF THE TURTLE BY THE CATHODE RAY OSCILLOGRAPH

Abstract

Conduction through the cervical sympathetic ganglia of the turtle of the fiber types present in this nerve was studied in Chrysemis picta, C. marginata and Pseudemys concinnata. The nerve lacks the 1st component of fibers characteristic of somatic nerves. The 1st, or B1, potential of this nerve when present pre- and postganglionically conducts through the ganglion in both directions without apparent delay. This fact, together with the evidence that the fibers giving rise to it have physiological and histological characteristics similar to those of fibers considered to be afferent in autonomic and somatic nerve trunks, seems to warrant the conclusion that the fibers of the B1 potential are afferent. The major portion of the fibers of the B2 potential and all fibers giving rise to the C potential synapse in the superior sympathetic ganglion. The action potentials of such fibers do not conduct toward the central nervous system through the ganglion. In turtles having 1 or more proximal ganglia besides the customary superior a small number of B2 fibers conduct through the superior cervical ganglion in both directions without delay. These fibers have synapsed in the more proximal ganglia. Postganglionically they conduct more slowly than the rest of the B2 fibers. No evidence of afferent C fibers has been obtained. In the turtle superior cervical ganglion, preganglionic myelinated or B2 fibers are found to synapse with postganglionic myelinated or B2 fibers, and unmyelinated C preganglionic fibers to synapse with unmyelinated C postganglionic fibers. In fresh preparations the synapse time as determined by delay in conduction rate and by absolutely refractory period times varies from 8 to 15 [alpha] for the B2 potential and from 20 to 30 [alpha] for the C potential. These times are proportional to their respective thresholds and conduction rates. A method for determining the presence of a synapse in a ganglion by the use of CO2 is described.