When a person takes a puff from a cigarette, nicotine floods the brain, locks into receptors on the surface of the neurons, and produces feelings of happiness.
But nicotine does not just stay on the surface of the cells, it penetrates the nerve cells and changes them from the inside to the outside.
When nicotine molecules enter the body, they travel through the bloodstream and reach the brain cells where they encounter nicotinic receptors (nAChRs) on the surface of these cells. This activates cell processes to release chemicals of reward and happiness.
Scientists discovered that neurons become more sensitive to nicotine, which enhances the feelings of reward after a puff of a cigarette or an electronic cigarette.
In other words, the more one smokes, the more quickly and easily the smoker gets the nicotine. This is part of the nicotine addiction.
Source: doctorsformulas.com