Nicotine is one of the most addictive substances know to human kind. It can become an addiction in the same way as the use of alcohol, tranquilizers and other drugs. In its pure form, nicotine is a strong poison. A small dose of it, injected directly into the bloodstream, would kill a person within an hour. Because it is inhaled, it only takes seven to 10 seconds to reach the brain – twice as fast as intravenous drugs and three times faster than alcohol.
Once there, it mimics some of the actions of adrenaline. After a few puffs, the level of nicotine in the blood skyrockets, the heart beats faster and the blood pressure increases. The result is that the smoker feels more alert and may actually think faster.
In addition, nicotine may produce a calming effect by triggering the release of natural opiates called beta-endorphins. Thus, smoking produces two feelings: alertness and calmness.
Since nicotine can’t be stored in the body, smokers smoke more to maintain a relatively constant level in the blood and therefore suffer withdrawal symptoms when use of the substance is stopped.