CHAPTER XLI II 



The neural control of respiration 



R. J. H. OBERHOLZER 

 W. O. TOFANI 



Department of Physiologv, ^iirich University, ^uric/i, Switzerland 



CHAPTER CONTENTS 



Anatomical Localization of Respiratory Centers 



Primary Respiratory Centers in the Medulla Oblongata 



Primary Respiratory Centers in the Pons 



Structures of Higher Brain Stem Involved in Respiratory 



Regulation 

 Cortical and Cerebellar Influence on Respiratory Activity 

 Spinal Respiratory Centers and Descending Respiratory 

 Tracts 

 Intrinsic Control of Respiratory Activity 



Assumed Mechanisms Leading to Rhythmic Respiration 

 Intrinsic Mechanisms Leading to Modification of Basic 



Respiratory Rhythms 

 Respiratory Neural Discharge 

 Extrinsic Control of Respiration 

 Vagal Control of Respiration 

 Vagal proprioceptive control 

 Vagal chemoreceptive control 

 Role of the Carotid Body in Respiratory Control 

 Pressoreceptor Influence on Respiration 

 Proprioceptive and Protective Respiratory Reflexes 

 Hyperpnea Associated with Muscular Activity 



THE EXPRESSION 'RESPIRATION,' as Used in this section, 

 refers only to external respiration, in particular to the 

 nervous control of the respiratory muscles. Because of 

 the incorporation of the gas-exchange surfaces within 

 the body, the activity of these muscles must be a 

 rhythmic one; for functional reasons it must be 

 autonomous. Furthermore, pulmonary ventilation — 

 the result and measure of respiratory activity — must 

 be, through chemical or nervous reflex mechanisms, 

 continually adapted to the needs of the body. The 

 protection of the respiratory organs is also mediated 

 through special nervous mechanisms, and the estab- 

 lishment of contact between individuals throusjh the 



medium of speech requires some means of cortical 

 control of respiration. In connection with the manifold 

 functions which respiration subserves, various ques- 

 tions arise as to the position of the respiratory centers, 

 the causes and mechanisms of their automatic 

 rhythmicity, and the possibility of nervously coordi- 

 nated adaptive processes. 



In 1 812 the respiratory center was located for the 

 first time in the medulla oblongata by Legallois (121, 

 122). His experiments were repeated by Flourens (66, 

 67) who located the respiratory center in a narrowly 

 circumscribed area at the level of the calamus scrip- 

 torius of the medulla oblongata, in the so-called 

 noeud vital. But various attempts to confirm these 

 assertions led, already in the nineteenth century, to 

 the discovery of additional spinal, pontine, mesen- 

 cephalic and diencephalic, as well as cortical, nervous 

 structures which also participate in respiratory regu- 

 lation. Today it is customary to separate a primary 

 respiratory center in the reticular substance of the 

 medulla and pons from the superimposed or secondary 

 respiratory centers in the mesencephalon and dien- 

 cephalon, as also from the spinal effector centers in 

 the spinal cord. 



An adaptation of respiration to changing bodily 

 needs can result through a change in the frequency of 

 respiration, a change in the respiratory amplitude, or 

 through both changes occurring concurrently. Con- 

 sidered from a neurophysiological point of view, as 

 well as in regard to energy expenditure, the means 

 through which the adaptation occurs is by no means a 

 matter of indifference. Therefore, in the following, we 

 shall attempt to avoid using the customary clinical 

 expressions 'respiratory activation,' and 'respiratory 

 inhiijition,' substituting therefore the somewhat more 



