Tobacco contains a multitude of harmful chemicals, including substances associated with cancer and other diseases. Nicotine is the chemical that keeps people smoking, chewing or sniffing tobacco. Because of its effects on the brain, nicotine is physically and psychologically addicting. These effects can make it very difficult for people to stop using tobacco once it becomes a habit.
Amounts
An average smoker inhales 1 to 2 mg of nicotine per cigarette, according to the National Institute on Drug Abuse (NIDA). Because nicotine reaches the brain rapidly, every puff delivers a separate hit of the drug. At a pack a day, with 10 puffs on each cigarette, this amounts to 200 hits of nicotine per day. Even when not inhaling the smoke or when using smokeless tobacco, people still absorb nicotine through their mucous membranes.
Effects
Nicotine intake stimulates the adrenal glands, causing a rush of epinephrine (adrenaline). This leads to an increase in respiration and an increase in heart rate by about 10 to 20 beats per minute, states MedlinePlus. Nicotine causes narrowing of blood vessels, leading to an increase in blood pressure by 5 to 10 mmHg. It also increases bowel activity, which may result in diarrhea. Additionally, nicotine also suppresses appetite, raises blood sugar levels and increases insulin, saliva and bronchial secretions.
Acetylcholine
Nerve cells communicate with chemicals called neurotransmitters. Each neurotransmitter activates a nerve cell by fitting into a specific type of receptor on the surface of that cell. Nicotine is shaped like the neurotransmitter acetylcholine and attaches to those receptors. This causes effects associated with acetylcholine activity, including improvement of concentration, memory, learning ability and alertness. It also allows the release of other neurotransmitters, including dopamine.
Dopamine
An increase in dopamine at the level caused by smoking or chewing tobacco elevates mood, producing feelings of pleasure and well-being and, sometimes, even euphoria. Nicotine use can actually relieve minor depression. This temporary dopamine elevation is part of the nicotine addiction process, as the tobacco user continues to desire more of that feeling once it dissipates. Because of its effects on dopamine, nicotine can cause addiction similar to that involved with the use of alcohol, cocaine, morphine and, even, heroin, reports MedlinePlus.
Significance
Nicotine is both physically and psychologically addictive. Stopping tobacco use typically causes withdrawal symptoms, including strong cravings for tobacco, along with anxiety, irritability, anger, restlessness, difficulty concentrating, feelings of depression, increased hunger, trouble sleeping and constipation or diarrhea. Users also may crave the pleasurable effects of nicotine long after physical withdrawal has subsided. Yet, smoking, chewing or sniffing this substance on a long-term basis can be dangerous to your health. Tobacco contains hundreds of harmful chemicals, including at least 19 cancer-causing chemicals, typically referred to as a group called "tar," explains MedlinePlus. Smoking tobacco also produces gases, including carbon monoxide and hydrogen cyanide, which can have negative effects on your health. Smokers have significantly higher rates of cancer, as well as cardiovascular and lung disease.
