Video - Sympathetic nervous system

The sympathetic nervous system is a part of the autonomic nervous system (ANS) that helps regulate the body's involuntary functions such as breathing, digestion, heart rate, and blood pressure. It is based on a preganglionic or cholinergic neuron that releases acetylcholine and a postganglionic neuron that releases either catecholamines or acetylcholine to a target cell.

The sympathetic nervous system is often referred to as the fight or flight system because it helps prepare the body for action in response to a threatening or stressful situation. In emergency situations, the activity of the sympathetic nervous system increases and diverts blood away from the organs that are not necessary for survival, like the gastrointestinal tract and the bladder, and increases blood flow to muscles and organs like the brain. The sympathetic nervous system works in opposition to the parasympathetic nervous system, which helps the body to relax and conserve energy.