Cardiovascular Responses Of The Turtle Pseudemys Scripta To Anoxia And Hypercapnia (blood Flow)

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Degree Name

Doctor of Philosophy (Ph.D.)


Marine Biology and Fisheries


The cardiovascular response of the red eared slider (Pseudemys scripta) to anoxia and hypercapnia was monitored with arterial cannulae and radiolabelled microspheres. During breath hold induced hypoxia a 34% bradycardia and a 42% fall in cardiac output occurred after 90 min of apnea. Blood flow to the brain increased dramatically, rising nearly 8 fold (to 0.085 ml/g/min) despite a fall in cardiac output. The eyes and muscle also experienced increases in flow while the heart, liver, stomach, small intestine, large intestine, pancreas, spleen and kidneys all underwent progressive decreases in flow. Hypercapnia alone, induced through the respiration of air with 12% CO(,2) did not cause a fall in heart rate, blood pressure or cardiac output. It did however, result in a redistribution of blood flow with the brain perfusion increasing nearly 8 fold and stomach, small and large intestines, pancreas, and muscle undergoing declines in flow. Heart, liver and kidneys experienced no change in perfusion.Carotid and femoral arterial blood was equally oxygenated during air breathing and apnea indicating no selective intracardiac shunting of oxygenated blood to the head. Brain O(,2) consumption (0.138 ml/g/hr) was twice that of leg skeletal muscle and remained constant even during severe hypoxia. Both tissues maintained O(,2) extraction efficiency during apnea and utilized essentially all available O(,2). An in vivo blood dissociation curve showed the blood had an O(,2) capacity of 9.9 vol%, a P(,50) of 27.9 mmHg and a Hill coefficient of 1.87. Blood glucose and lactate rose during apnea as a result of increased glycolysis.During apnea blood cations (K('+), Ca('2+), Mg('2+)) and catecholamines (norepinephrine, epinephrine, dopamine) all rose in response to apnea, probably contributing to the cardiovascular system's apneic response.


Biology, Animal Physiology

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