REFLEXOGENIC COMPONENTS OF BREATHING

Abstract

The reflexogenic drive of the respiratory act is analyzed by stimulation of 3 types of nerves (predominantly proprioceptive, chemo-ceptive or nociceptive). Prolonged faradic stimulation of the vagal afferents during expiration produced a prolonga-tion of the expiratory phase thus preventing the normal recurrence of the inspiratory cycles. Stimulation beginning during the inspiratory phase produced a temporary intensification of the inspiratory act followed by the usual prolongation of the expiratory phase. Intensification and prolongation of expiration classified vagal stimulation as predominantly expiratory. Similar stimulation of Hering''s nerve produced rhythmic breathing in which both inspiration and expiration were intensified. The increased drive was predominantly inspiratory. Faradic stimulation of the saphenous nerve produced rapid rhythmic breathing in which the inspiratory and expiratory components were more evenly intensified. Intermittently interrupted faradic stimulation of any of these dual excitatory nerves produced a selective excitation of either the inspiratory or expiratory half center depending upon the phase of respiratory activity existing at the moment of stimulation. This precedence of stimulation held for more abnormal situations as well. A sustained expiratory activity produced by stimulation of either the vagus or superior laryngeal nerve was intensified by faradic stimulation of either the saphenous or Hering''s nerve to the exclusion of inspiratory effects. Similar addi-tion of inspiratory drives was demonstrated. Selective sum-mation of either inspiratory or expiratory drives from diverse receptors indicates a commonness of action of excitatory signals impinging on a single nerve cell and confirms earlier considerations that the sum total of imping-ing signals constitutes the power which drives the c. n. s.