#sympathetic-nervous-system

#sympathetic-nervous-system

The first part, the immediate loss of hair, was simple. "Stress has an immediate impact through the activation of the sympathetic nervous system," explained Hsu, who is also a principal faculty member of the Harvard Stem Cell Institute. She said that it begins with our natural "fight or flight" response, which releases norepinephrine, a neurotransmitter that - among other effects - kills highly proliferating cells in the hair follicle when the level is too high. Hair loss in such circumstances is usually temporary.

Biologists long have been fascinated by the ability of salamanders to regrow entire limbs. Now Harvard researchers have solved part of the mystery of how they accomplish this feat - by activating stem cells throughout the body, not just at the injury site. In a new paper published in the journal Cell, researchers documented how this bodywide response in axolotl salamanders is triggered by the sympathetic nervous system, or the "fight or flight" network.