Interaction of Central and Peripheral Inputs onto Vagal Cardiomotor Neurones

Abstract

The present meeting is concerned with unravelling the central mechanisms responsible for the interactions between the control of the respiratory and cardiovascular systems. That such an interaction exists is clearly demonstrated by considering the vagal control of the heart. Sinus arrhythmia, the phasic fluctuations in heart rate seen during natural respiration, has been shown to be mediated primarily by the vagal efferent supply to the heart (1, see Daly, Session V). Further, it has been demonstrated that these phasic changes in vagal efferent activity result from two main mechanisms; the first of central origin and arising from the neural processes generating respiratory activity, the second of peripheral origin as a consequence of lung inflation (1, 2). In addition a recurring theme throughout this meeting will be the nature of the influence of respiration on the performance of both baroreceptor and chemoreceptor reflexes (see McCloskey, Daly, Session V). Indeed, as long ago as 1961, Koepchen and co-workers (3, 4) described the effects of respiration on the response of the heart, mediated by the vagus, to electrical stimulation of the sinus nerve.