Heart Rate Perturbations

Abstract

To further substantiate the importance of metabolism as the primary factor, affecting the movement of blood, let us look at experiments in which the metabolic rate has been changed by subjecting the embryo to environmental hypo- or hyperthermia. Since the chick embryo is poikilothermic, its hemodynamic functions are exquisitely sensitive to change in temperature. When the temperature was raised from 37 to 40 °C in HH stages 18, 21, and 24 chick embryos, there was a linear increase in heart rate and aortic flow, while the stroke volume remained unchanged [1]. Similarly, a global decrease in temperature to 31.1 °C in the chick embryos at the same developmental stages resulted in a proportional decrease in heart rate, vitelline artery pressure, and aortic flow and no change in stroke volume [2].