Effect of sinusoidal forcing of ventilatory volume on avian breathing frequency

Abstract

Awake chickens were unidirectionally ventilated at 3.6 l . min-1 with 3.2-4.8% CO2 in air. The air sacs on each side were made confluent and implanted with exit tubes connected to the following three devices: 1) a system of constant-flow generators which remove air at exactly the same rate that it entered the trachea, allowing no port for spontaneous volume changes; 2) a sinusoidal pump to force volume changes in the chicken; and 3) a pressure transducer to record air sac pressure, which reflected the sum of two pressure components, the passive pressure changes created by the pump and the active pressure changes due to breathing efforts. Over a range of pump frequencies, the amplitude of measured air sac pressure changes varied inversely with frequency. Above and below this range, pressure showed a beat pattern, indicating a difference in the frequencies of the two pressure components. Within the range lacking a beat pattern, breathing movements and the pump stroke had the same frequency. This range was greater at increased stroke volume. Breathing efforts worked with the pump at the high end of the range and against the pump at the low end. These findings show further evidence of the presence of a response to volume forcing and fit a previously described volume threshold model.

Sound‐induced stabilization of breathing and moving

“…In animals, neurological factors have been offered as a complementary origin of LRC, characterized by a common control for respiration and locomotion at both cortical and medullar levels . Furthermore, movement‐based sensory afferents have been shown to inform respiratory centers in the medulla, including simple rhythmic peripheral tactile stimulation . This neuromotor modulation of respiration is, however, still to be confirmed in humans.…”

Vagal innervation of the air sacs in a songbird, Taenopygia guttata

“…1978). Some of the innervation seems likely to be supplied by the vagus nerve, because changes in the volume of the air sacs, without a change in , have been shown to affect ventilatory timing, and this effect is dependent on an intact vagus (Ballam et al. 1982, 1985; Gleeson & Molony, 1989).…”