respond to these challenges. Our actions vary, adapted for the lifestyles we maintain in different environments, but much of our basic cellular machinery is the same. Biology kept it that way: If it ain’t broke, don’t fix it.
One mechanism our cells share is fluctuating levels of calcium ions, which carry an electrical charge. In humans, this charge assists in controlling when your neurons fire messages. Changes in calcium ions make your heart beat or your muscles contract so you can get up and leave when something threatens you.