The momenta of individual objects changes. The total momentum remains constant. I have to disagree. If you have two cars that collide head on, the momentum of both vehicles stops. The ENERGY created by the impact causes usually, some reverse momentum but the momentum is lost.
As the SNS continues to trigger physical reactions, it causes a wear-and-tear on the body. It's not so much what chronic stress does to the nervous system, but what continuous activation of the nervous system does to other bodily systems that become problematic.
The sympathetic nerve system is used by your body in response to stress, or, in other words, anything that your body perceives as a threat. Acting intelligently, your bodyâs response to threats is to prepare for action: fight-or-flight. Even thinking of a stressful event will cause you to experience the influence of the sympathetic nerve system in your body. To do this, however, there is a cost.