Nicotine
Nicotine, named after Jean Nicot, is an organic compound, an alkaloid found naturally throughout the tobacco plant, with a high concentration in the leaves. It constitutes circa 5% of the plant by weight. It is a potent poison and is included in many insecticides.
The substance is a powerful stimulant and is one of the main factors leading to the addictiveness of tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause addiction. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. On average it takes about seven seconds for the substance to reach the brain.
Effects on the body
In small doses nicotine has a stimulating effect. It enters the bloodstream and promotes the flow of adrenaline, a stimulating hormone. Nicotine also speeds up the heartbeat, raises the blood pressure and reduces the appetite. In large doses it may cause vomiting and nausea. Withdrawal symptoms include irritability, headaches and anxiety. These symptoms may last for 48-72 hours.