The hormonal substance that promotes arousal is noradrenaline. Orexin “Orexin” is a substance that maintains arousal in a state of high emotions. When something you don’t know or anxiety accompanies, it causes psychological stress and cortisol “Cortisol” is secreted to increase the inducibility. It has been found that when the stress that cortisol continues to secrete continues, cortisol atrophies the hippocampus of the brain and increases the risk of psychological disorders and depression. In this way, neurotransmitters produced in the nervous system and organs influence evokedness and alertness and work to generate emotions. The stress generated in this process leads to a decrease in immunity.