ABSTRACT
Phrenic motoneuron activity is controlled by efferent drive emanating from pontine and medullary respiratory controllers. The activity of these controllers is influenced by inputs from higher centers, as well as by afferent inputs from various peripheral effectors. These peripheral afferent inputs provide the respiratory controllers with essential feedback concerning the functional status of these effectors to aid the respiratory controllers in modulating their output in accordance with the mechanical activity and metabolic needs of the peripheral organs. Although several of these afferent inputs, such as vagal and skeletal muscle afferent sources, had received considerable attention in the past, the functional significance of afferent inputs originating from the respiratory muscles, particularly the diaphragm, in the modulation of central respiratory output, received much less attention. Moreover, the available data on physiological properties of phrenic afferents have been a source of considerable debate.
