ARE MASS DISCHARGES CHARACTERISTIC OF CENTRAL AUTONOMIC STRUCTURES?

Publisher Website
Google Scholar
Abstract
The effect of electrical stimulation of the dorsal surface of the spinal cord at various levels as well as excitation of autonomic structures in the medulla oblongata and hypothalamus was studied in order to determine whether maximal sympathetic reactions thus elicited involve the whole sympathetic system or not. Stimulation of the spinal cord showed that the autonomic discharges are largely segmental. At T4 a maximal rise in blood pressure may be elicited without sympathetic ocular symptoms. Ascending from T3 to T1 the cilio-spinal center is brought into action to an increasing degree while the pressor reaction gradually disappears. The cilio-spinal center may be excited partially from T1 to T3, the medulla oblongata, and the hypothalamus resulting in contraction of the nictitating membrane without excitation of the dilator pupillae. The converse phenomenon, maximal pupillary dilatation without involvement of the nictitating membrane has been obtained from the hypothalamus. Studies of heart rate, pupillary diameter and nictitating membrane show that maximal discharge of the cilio-spinal center may follow hypothalamic stimulation without alteration in heart rate. The explana-tion of the fact that spinal stimulation may lead to maximal discharge in one branch of the sympathetic system without causing a noticeable excitation of another seems to be based on the segmental arrangement of autonomic functions in the spinal cord. That similar effects may result from stimulation of sympathetic centers in medulla oblongata and hypothalamus appears to be due to unequal numerical distribution and marked differences in threshold of neurons mediating the various specific sympathetic functions. The expts. imply that central excitation of autonomic centers under physiologic and pathologic conditions may lead to but a partial discharge of the sympathetic system. It is suggested that the mass discharge of this system in emotion and other conditions is due to the excitation of relatively large central areas.

This publication has 4 references indexed in Scilit: