Rabbits and other warm-blooded mammals, on the other hand, can accommodate higher heart rates necessary to sustain an active, endothermic metabolism but they face increased risk of cardiac arrhythmia and critical vulnerability to temperature changes. While alligators can function over a large temperature range without risk of heart trauma, their built-in safeguard has a drawback: it limits their maximum heart rate, making them unable to expend extra energy in an emergency. "We found that when the spatial wavelength reaches the size of the heart, the rabbit can undergo spontaneous fibrillation, but the alligator would always maintain this wavelength within a safe regime," he added. "The excitation wave in the rabbit heart reduced by more than half during temperature extremes while the alligator heart showed changes of only about 10% at most," said Conner Herndon, a co-author and a graduate research assistant in the School of Physics. For example, if someone falls into cold water and gets hypothermia, very often this person will develop an arrythmia and then drown," Fenton said.ĭuring the study, the researchers recorded changes in the heart wave patterns at 38 C and 23 C. "An arrhythmia can happen for many reasons, including temperature dropping. In a deadly arrhythmia, this electrical signal is no longer coherent. An electrical signal drives this wave, which must occur in the same pattern to keep blood pumping normally. Heart pumping is controlled by an electrical wave that tells the muscle cells to contract. Both species have four-chambered hearts of similar size (about 3 cm) however, while rabbits maintain a constant heart temperature of 38 degrees Celsius, the body temperature of active, wild alligators ranges from 10 to 37 degrees Celsius. The study looked at the action potential wavelengths of rabbit and young alligator hearts. Fibrillation is one of the most dangerous arrhythmias, leading to blood clots and stroke when occurring in the atria and to death within minutes when it happens in the ventricles. They're very resilient," said Flavio Fenton, a professor in the School of Physics at the Georgia Institute of Technology, researcher in the Petit Institute for Bioengineering and Bioscience, and the report's corresponding author. "Alligator hearts don't fibrillate - no matter what we do.
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