Nicotine is a highly addictive, poisonous chemical substance found in tobacco leaves. Most nicotine is derived from a plant called Nicotiana tabacum, but there are many other species of plants that contain nicotine. It’s believed that Aborigines may have been among the first people to use tobacco.
When you inhale tobacco smoke, it takes about four seconds for nicotine to reach your bloodstream and about 10 seconds to reach your brain. When it reaches certain areas of your brain, it releases relaxing chemicals. This effect only lasts a short time, so that’s why smokers need to keep topping up.
Nicotine is also a stimulant and an appetite suppressant. Other effects include increased heart rate and blood pressure, and constriction of blood vessels. Over time, ingestion of nicotine from smoking combines with carbon monoxide to damage the lining of blood vessels and make blood platelets stickier. This can help cause heart disease. Smoking tobacco also causes lung cancer and other forms of cancer, as well as many other respiratory (breathing) diseases.