The Role of Segmental Reflex Mechanisms in the Regulation of Breathing

Abstract

Comparatively little information is available concerning the role of proprioceptive discharges in the regulation of breathing, especially with regard to their segmental reflex actions. Some information concerning their importance has come from studies of the effects of cutting the cervical and thoracic dorsal roots. Coombs (1918) found that section of thoracic dorsal roots greatly diminished intercostal movements in the cat, and even abolished them in the kitten (Coombs and Pike 1930). Stella (1938) claimed that cutting all the thoracic and cervical roots is without effect on breathing, but his cats showed only diaphragmatic respiration before the dorsal roots were cut, so that his results cannot be held as being at variance with those of Coombs on costal respiration as stated by some authors. In confirmation of Stella (1938), Sant’Ambrogio, Wilson and Frazier (1962) found no evidence from cervical dorsal root section for a significant proprioceptive afferent inflow from the cat diaphragm. On the other hand, a temporary paralysis of the hemi-diaphragm results from unilateral cervical dorsal root section in man (Nathan and Sears 1960), thus indicating a possible species variation. Sears (1958; see also 1964 c) limited the section of thoracic dorsal roots usually to one segment and determined electromyographically its effects on the intercostal and abdominal muscles innervated from that segment.