Coordinated Control of Respiratory Pattern During Locomotion in Birds

Abstract

SYNOPSIS. Cineradiographic studies of magpies and pigeons in flight, coupled with measurements of air sac pressures and tracneal airflows, indicate a significant compressive effect of downstroke and expansive effect of upstroke. These mechanical impacts of the wingbeat cycle upon the respiratory system likely contribute to a phasic coordination of the two cycles that, in these species, ensures that upstroke corresponds to the transition into inspiration and downstroke corresponds to the transition into expiration, regardless of the ratio of wingbeats to breaths. Similar phasic patterns have been reported for other birds. Respiratory muscle activity patterns indicate that the upstroke may indeed assist inspiratory airflow and that the downstroke may assist expiratory airflow. Stimulation of ventilation with 5% CO2 during flight did not alter the phasic coordination patterns between respiratory and wingbeat cycles in either pigeons or magpies. These data support the concepts that 1) interactions of locomotor and respiratory central controllers likely play an important role in regulating respiratory pattern during locomotion in birds and 2) peripheral neural feedback of information about the mechanical impact of the wingbeat cycle upon the functioning of the respiratory pump is likely to make a strong contribution to a respiratory pattern that is coordinated with the locomotor pattern in an energetically appropriate phasic relationship. The failure to alter that pattern with chemical stimulation of breathing suggests that the neural interaction between locomotor and respiratory networks is quite robust