The tobacco plant is called Nicotiana tabacum and is named after an early importer named Jean Nicot. In 1828, nicotine was isolated from the leaves of the tobacco plant. American cigarettes contain about 9 mg of nicotine, but since much of the nicotine is burned off, a smoker gets about 1 mg of nicotine in every cigarette. Nicotine reaches the central nervous system in about 3-5 minutes when tobacco is chewed. Smoking can be stimulating or relaxing - it depends on a person's mood and dosage of nicotine.
Nicotine acts on the central and peripheral nervous system.
Long term exposure to tobacco and nicotine increases the chances of cancer and results in addiction and dependence. Exactly how nicotine produces addiction and dependence is not clear, but there are some theories . In the brain, limbic pathways that use the neurotransmitter dopamine are affected by nicotine and may be responsible for some of the addictive properties. According to the World Health Organization , there are 1.1 billion smokers worldwide and 6000 billion cigarettes are smoked every year. These two men wanted to see who could smoke the most cigarettes at a single sitting.