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.
This is the point where temporary soreness turns into chronic pain, where that dull, nagging ache becomes the new normal. It affects more than just your muscles. Your sleep suffers. Your energy drops. Over time, your brain circuits that process pain grow more sensitive, creating a vicious cycle that's hard to break. What determines whether you bounce back or break down? That's the question researchers at the State University of Campinas in Brazil set out to answer.
When a booster vaccine was administered in the same location as the initial dose, the mice's subcapsular sinus macrophages were already primed. They reactivated immune cells called memory B cells more quickly.