The National Institute of Drug Abuse for Teens says that one drop of nicotine in its pure form is toxic enough to kill. Though concentrations of nicotine in cigarettes are much weaker, they are still potent enough to cause life-threatening diseases. The American Lung Association cites smoking cigarettes as the cause of 392,000 deaths in the U.S. each year, making it the leading cause of preventable death.
Cardiac and Respiratory Effects
Nicotine increases the heart rate, causing the pulse to quicken. The veins in the body constrict, which makes the blood pressure go up temporarily. Nicotine also affects nerves related to respiration which can affect the breathing pattern.
Central Nervous System Effects
Nicotine enters the brain within 8 seconds of smoking, according to the National Institute of Drug Abuse, or NIDA, for Teens. Nicotine is similar to a neurotransmitter in the brain called acetylcholine. It can trick the brain by activating feelings of pleasure and reward. Nicotine stimulates and sedates the central nervous system. The adrenal glands pump out adrenaline which increases metabolism and makes the heart rate go up. It also results in the relaxation of smooth muscle.
When exposed to nicotine, the body develops a tolerance for it. This can lead to an addiction because more nicotine in the body is needed to maintain the effect of the drug. Quitting smoking leads to withdrawal symptoms that can be difficult to cope with. NIDA for Teens reports that people who start smoking before the age of 21 have the hardest time quitting; fewer than one in 10 people who try to quit smoking succeed. Smoking cessation can sometimes take several attempts, but the benefits are worth the effort.
An addiction to nicotine can lead to a smoking habit. Smoking causes many cancers, and increases the chances for serious chronic lung diseases. In addition, other diseases such as heart disease and diabetes are linked to smoking. The American Lung Association reports that 8.6 million people in the U.S. have at least one serious illness caused by smoking.