This winter in North America has been unseasonably warm. However, as they always do, hibernating animals tend to follow their natural patterns by lowering their metabolism and sleeping through most of it. Along with a slow metabolism comes a lower body temperature, less need to eat, and a reduced heart rate. According to a new study presented at the 56th Annual Meeting of the Biophysical Society (BPS) in San Diego, California, the lower heart rate in hibernating animals can make them prone to cardiac arrhythmia, abnormal heart rhythms. If the slumbering creature cannot sequester enough calcium for its muscle cells, this could lead to sudden cardiac death.
This winter in North America has been unseasonably warm. However, as they always do, hibernating animals tend to follow their natural patterns by lowering their metabolism and sleeping through most of the winter. Along with a slow metabolism comes a lower body temperature, less need to eat, and a reduced heart rate. According to a new study presented at the 56th Annual Meeting of the Biophysical Society (BPS) in San Diego, California, the lower heart rate in hibernating animals can make them prone to cardiac arrhythmia, abnormal heart rhythms. If the slumbering creature cannot sequester enough calcium for its muscle cells, this could lead to sudden cardiac death.
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For most hibernating creatures, they can be awakened from their slumber by external stimuli. A sleeping bat in a tree will wake up if the tree falls down. A sleeping bear will likely wake up if a hiker walks into its cave.
However, there are certain creatures known as "true hibernators" that enter a profoundly different physiological state during the winter. Falling into this category are woodchucks, also known as groundhogs. They body temperature can fall to near-ambient levels, even just on the cusp of the freezing point. Their heart rates and breathing rates also fall accordingly.
Due to these evolutionary winter adaptations, hibernating animals are believed to be more resistant to cardiac arrhythmias and sudden death.
Researchers from the University of Medicine and Dentistry of New Jersey (UMDNJ) – Jersey Medical School in Newark, studied this phenomenon by examining the muscle cells in woodchucks over the winter and summer months. In particular, they monitored the release and uptake of calcium ions when the cells were activated.
They found that during the winter, the muscle cells had less spontaneous leakage of calcium. When the animals became aroused, more calcium was released, but was reabsorbed much quicker than during the summer. The researchers believe this mechanism prevents abnormal changes in the heart's electrical activities, helping it maintain a steadier rhythm.
More study into the woodchuck's natural ability to prevent cardiac arrhythmia may aid in protecting non-hibernating animals, particularly humans.
Link to presentation abstract
Groundhog image via Shutterstock
