Smoking is the number one cause of preventable death in the United States. Approximately one in every five deaths is due to complications related to smoking. The harmful effects of smoking are due to several factors including the smoke from tobacco, nicotine, and other non-tobacco substances that are included in a cigarette. What is Nicotine? Nicotine is a basic alkaloid, or a naturally occurring chemical, that has strong psychological effects. In its pure form, it is a clear liquid with a strong odor that turns brown when exposed to air. Nicotine can be absorbed through various membranous tissues including the lungs, skin, stomach, or mucus membranes lining the mouth. Its ability to pass through these membranes depends on its pH. The higher or more basic the nicotine is, the easier it can pass through the tissue. It primarily targets the nervous system. Mechanism of Nicotine Action When smoking a cigarette, nicotine travels into the body through smoke particles into the lungs. There it is absorbed into the pulmonary veins, which are blood vessels that collect oxygen from the lungs and displace the blood in the left atrium of the heart. The nicotine enriched blood is then pumped into arterial circulation which allows it to reach the brain.