Nervous control of heart rate during excitement in the adult White Leghorn cock.

TUMMONS,JOHN L., AND PAUL D. STURKIE. Nervous control of heart rate during excitement in the adult White Leghorn cock. Am. J. Physiol. 216(6): 1437-1440. 1969.-The control of heart rate by the sympathetics and parasympathetics during excitement has been studied in the adult White Leghorn cock. The data presented in this study demonstrate that at the basal resting heart rate (BRHR) of 280-290 beats/min there appears to be present a significant amount of sympathetic and parasympathetic tone. This tone appears approximately balanced, as elimination of either nerve system resulted in approximately equal changes in the BRHR (increase or decrease). In the normal bird excitement-induced heart rate changes appear to result from a decrease in the resting vagal tone and increased sympathetic tone, with all immediate increases in heart rate above the BRHR level dependent on sympathetic tone. The normal BRHR can be maintained in the absence of extrinsic cardiac nerves. Complete denervation first becomes evident in the inability of the bird to significantly change its heart rate in immediate (O-6 set) response to excitement.