A FUNCTIONAL ANALYSIS OF THE CERVICAL SYMPATHETIC NERVE SUPPLY TO THE EYE

Abstract

The cervical sympathetic trunk of the cat contains sensory myelinated axons of vagus origin, responsible for its most rapidly conducting potential wave; the rabbit lacks these, the separate depressor presumably containing them. Two groups of motor axons which are myelinated in both animals pre-ganglionically give 2 potential waves partially super-imposed. A 3rd group of unmyelinated motor axons gives a wave propagating much more slowly. Stimulation of the 1st motor group causes dilatation of the pupil and retraction of the nictitating membrane; of the 2nd, constriction of blood vessels in eye and ear, and in the cat, pilomotor responses. No response was detected to stimulation of the last group. Postganglionically, the 1st group of motor myelinated axons synapses with myelinated axons in the cat, with unmyelinated axons in the rabbit. The 2nd group synapses with unmyelinated axons in both animals, likewise the last group. No repetitive response postganglionically to single stimuli preganglionically could be detected. The refractory period of the synapse is 15 to 20 sigma. The ganglion apparently acts as a distributive mechanism only, one preganglionic F1ber synapsing with several postganglionic. A strong stimulus activating many F1bers of one type only once, has the same effect as several weaker stimuli, the number of F1ber-stimuli being the signiF1cant factor, as if summation took place at the periphery. Cathode ray oscillograph records were made from the nerve in situ with coincident observations of nerve potentials and responses of the animal.