Liver Survives Cold Temperatures

photograph of brown squirrel during the day

Biological Strategy

Squirrels

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Maintain Homeostasis

When a living system is in homeostasis, it means that internal conditions are stable and relatively constant. For example, a human’s internal temperature is approximately 37 degrees Celsius (98.6 degrees Fahrenheit) unless there’s an illness. The human body maintains this temperature despite external ambient temperature. However, as with all physiological processes, maintaining homeostasis requires communication and coordination. So living systems have ways to detect changes from the norm, mechanisms to cause an adjustment, and negative feedback connections between the two. A desert lizard called the Gila monster offers a good example of maintaining homeostasis. The lizard goes from eating large meals to fasting for extended time periods. To maintain its blood sugar levels at a steady level, when food is scarce, its endocrine system releases a hormone that raises its blood sugar levels.

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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Livers of squirrels survive cold temperatures during hibernation by maintaining microcirculation.

“Close investigation of hibernating states is giving scientists new insight into animal physiology and, as a bonus, human health and disease as well…Organ transplant. Harvested human organs kept at cold temperatures can only remain viable for a few days at most. So, how do squirrels’ s and intestines stay perfectly healthy at less than 40 degrees Fahrenheit for weeks on end? In one study, ‘we found that [hibernating] squirrels maintain, in a much healthier state, the microcirculation of the liver,’ Carey said [Hannah Carey, a professor in the School of Veterinary Medicine at the University of Wisconsin-Madison]. Insights into just how this happens could increase the viability and number of human organs available for transplant, she said.” (Mundell 2007)

Last Updated August 18, 2016

References

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Groundhogs, other hibernators, could aid human health

HealthDay Reporter | Mundell, E.J.

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