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.
Noun. 1. sympathetic nervous system-originates in the thoracic regions of the spinal cord; opposes physiological effects of the parasympathetic: reduces digestive secretions; speeds the heart; contracts blood vessels.nervous system, systema nervosum-the sensory and control apparatus consisting of a network of nerve cells.oun. 1. sympathetic nervous system-originates in the thoracic regions of the spinal cord; opposes physiological effects of the parasympathetic: reduces digestive secretions; speeds the heart; contracts blood vessels.