Today, nearly a billion people on earth smoke cigarettes. Many have tried to stop, and they, too, find that smoking can be extremely difficult to give up. In the United States, four out of fives smokers say they want to “kick the habit”; each year fewer than one in ten succeeds. To see why, it is necessary to understand the effects of tobacco’s most powerful ingredient: nicotine.
Nicotine is an alkaloid poison found in tobacco leaves that defends the plant against insect attack. Nicotine affects the nervous system of insects and is sometimes an ingredient of insecticides. When small doses of pure nicotine are given to Rats, the result is instant death.
A cigarette contains an average of eight to nine milligrams of nicotine. However, some of this stays in the unsmoked remainder and some of it escapes into the air with the smoke. While the amount of nicotine inhaled with each puff is not poisonous, it does have powerful effects on a smoker’s nervous system. In fact, nicotine often causes a first-time smoker to feel dizzy and nauseous.
When tobacco smoke is held in the mouth, and not inhaled into the lungs, some nicotine is absorbed through the mucous membranes of the mouth and enters the bloodstream. The blood carrying the nicotine flows to the heart and is then pumped to the brain. Nicotine from chewing tobacco and snuff follows a similar route. However, when nicotine is drawn into the lungs, it passes more quickly into the bloodstream and on to the brain. Often less than ten seconds after a smoker inhales tobacco smoke, a tiny dose of nicotine arrives at his or her brain.
Once in the brain, molecules of nicotine that release of chemicals called neurotransmitters. For example, the release of a neurotransmitter called dopamine produces feelings of pleasure and suppresses appetite. Release of one called beta-endorphin reduces anxiety.
Smokers learn to regulate