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.
Sympathetic and Parasympathetic Effects. Effects on various systems and organs: Eye: dilation of pupil; focusing for distance vision. constriction of pupil; focusing for near vision. Skin: Sweat glands: (S) â increases secretion. (P) â none (not innervated) Arrector pili muscles: (S) â contraction and erection of hairs.