Flight or Fight Reaction Triggered By Bones Not Adrenaline

New research shows bones trigger the flight or fight reaction, not adrenaline pumping through our body.

Flight or Fight Reaction Triggered By Bones Not Adrenaline
A cat hoovering over its prey Vladyslav Ivashchenko/iStock

Ever wonder why some of us will stay and fight when faced with danger while others will hightail it out of there?

Apparently, researchers at Columbia Univerisity did and found its not adrenaline that prompts the "fight or flight" response but bones that trigger the reaction. 

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The hormone osteocalcin triggers flight or fight reaction 

When humans and animals are faced with a predator or sudden danger, the heart rate speeds up, breathing gets heavier and glucose is sent throughout the body to ready the person or animal to flee or stay and fight.

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The Columbia researchers found bony vertebrates need the skeleton to trigger that flight or fight reaction. According to their work, shortly after the brain computes danger, it sends a message to the skeleton to release into the bloodstream the hormone osteocalcin, which is necessary to turn on the fight or flight reaction. 

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"In bony vertebrates, the acute stress response is not possible without osteocalcin," said Gérard Karsenty, MD, Ph.D., chair of the Department of Genetics and Development at Columbia University Vagelos College of Physicians and Surgeons and the senior investigator on the study in a news release. "It completely changes how we think about how acute stress responses occur."

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Researchers have proven bones are more than calcified tubes

For a long time, researchers viewed bones as calcified tubes but work by Karsenty over the years showed the skeleton has influence over other organs in the body. Through his research, we learned the skeleton releases osteocalcin, which goes through the bloodstream and impacts the functions of the brain, muscles, pancreas and other organs in the body. Studies conducted more recently have demonstrated that osteocalcin helps regulate metabolism. 

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Since bones already protect organs from danger--the skull keeps the brain safe from trauma-- it's not a stretch that they will allow vertebrates to escape from danger. 

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Mice freak out when presented with predator urine

In order to confirm that theory, the researchers gave mice predator urine and other stressor and then studied the bloodstream to detect changes. In about two to three minues the osteocalcin level increased as did heart rate, body temperature and blood glucose levels as the fight or flight reaction kicked off. In humans, the researchers found osteocalcin increases when they have to speak in public or are cross-examined and are stressed out about it.

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Mice who were genetically engineered to not produce osteocalcin didn't have a reaction at all. "Without osteocalcin, they didn't react strongly to the perceived danger," Karsenty says. "In the wild, they'd have a short day."

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