title: Experimentally induced antagonism of chemical and thermal reflexes in the respiratory system of fully conscious chickens.
abstract: The joint response of the respiratory and panting centres of fully-conscious unidirectionally-ventilated chickens to simultaneous combinations of hyperthermia and hypo-/hypercapnia was examined. The response was monitored by changes in the rate and amplitude of movements of the body wall and gular apparatus respectively. The response to a combination of hyperthermia plus hypercapnia bore indications of a linear summation of the individual responses of the panting centre and respiratory centre to the respective thermal and chemical stimuli. A more complex response was elicited by a combination of hyperthermia plus hypocapnia. In this case the inhibition of respiratory movements induced by the hypocapnia (hypocapnic apnea) permitted a more forceful manifestation of the component of the thermoreflex which acts via the hyoid muscles and which is responsible for the synchronous 'gular flutterin'. The rate of gular fluttering increased by up to 150% as compared to normal panting. The experimental procedure therefore provided a technique for breaking the central linkage which normally constrains the rhythm of the hyoid muscles to the more dominant rhythm of the respiratory muscles.
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000502:physiology; D002645:Chickens / Q000502:physiology*; D006358:Hot Temperature; D006935:Hypercapnia; D008297:Male; D009132:Muscles / Q000502:physiology*; D012018:Reflex; D012119:Respiration