Breathing movements in the frog Rana pipiens. I. The mechanical events associated with lung and buccal ventilation

Abstract

The normal pattern of breathing movements in Rana pipiens has been studied by recording pressure and volume changes in the buccal cavity and lungs, and electromyograms from the muscles involved in this activity. Two types of breathing movement were obtained, one concerned with ventilation of the buccal cavity (buccal cycles) and the other with lung ventilation (lung cycles). Only in the latter type of movement were the nares and glottis actively involved. During buccal cycles the nares remained open and the glottis closed, so although excursions of the buccal floor were some two-thirds of the magnitude of those occurring during lung cycles, only low pressures were generated. The onset of a lung cycle was signalled by activity in the laryngeal dilator muscle. When the glottis opened, lung pressure and volume decreased, and buccal cavity pressure and volume increased. After closure of the nares, the buccal floor was rapidly elevated by the activity of the breathing muscles and air was forced into the lungs from the buccal cavity. At peak pressure in the lungs and buccal cavity the glottis closed and nares opened. The recovery stroke of the buccal pump was passive. No evidence was found for large pressure differentials between the buccal cavity and lungs when the glottis was open, and air-flow recordings at the external nares showed two phases of flow during each buccal cycle and four phases with each lung ventilation cycle.

Lung ventilation contributes to vertical lymph movement in anurans

“…Lung pressures range from 200 to 600·Pa during episodic ventilation in Bufo (Chaunus) marinus (Wang, 1994;Macintyre and Toews, 1976). Similar pressures have also been measured in Rana (Lithobates) pipiens (West and Jones, 1975;Vitalis and Shelton, 1990) and Rana (Lithobates) catesbeiana (Kinkead and Milsom, 1994). This suggests that the subvertebral sac, which adheres closely to the dorsal surface of the lung, may be a suitable location for measuring lung pressure in anurans.…”

Developmental changes in central O2 chemoreflex in Rana catesbeiana: the role of noradrenergic modulation

“…The motor output driving gill ventilation is characterised by its high frequency and low amplitude. In contrast, the command driving air breathing is less frequent but has greater amplitude as lung ventilation requires more forceful contraction of the buccal pump to push air into the lungs (Gans et al, 1969;West and Jones, 1975). These patterns of neural activity are produced by the in vitro brainstem preparations from both preparations (brainstems from tadpoles and adult frogs), even though air breathing is infrequent in premetamorphic tadpoles (McLean et al, 1995;Liao et al, 1996;Broch et al, 2002;Fournier and Kinkead, 2006).…”

Effects of maturation and acidosis on the chaos-like complexity of the neural respiratory output in the isolated brainstem of the tadpole,Rana esculenta

“…After metamorphosis, the gills degenerate. The adult animals breathe by propelling air into their lungs, again through buccal contractions (64). Between these lung breaths, smaller oscillations of the buccal floor persist, reminiscing gill ventilation (4,5).…”