Tobacco is the only natural source of nicotine and cigarettes have often been described as a “nicotine delivery device.” Nicotine is unusual because it can act as both a stimulant and a depressant when absorbed by the body. Why these dual reactions occur is not completely understood.

Nicotine reaches the brain within as little as 10 seconds. There, the nicotine changes the brain’s metabolic and electrical activity, as well as regulation of hormones and neurotransmitters (chemicals that control bodily functions). These changes cause the following negative reactions in the body:

• Increased heart rate by five to 10 beats per minute due to the release of a stress hormone (adrenaline).
  
  
• Constricted blood vessels, resulting in higher blood pressure.
  
  
• Greater collection of the body’s natural blood-clotters (platelets), which may lead to thrombosis (formation of blood clots), embolism (obstruction of a blood vessel by a clot) or heart attack.
  
  
• Increased saliva and sweat production.
  
  
• Increased bowel activity, which may result in diarrhea.
  
  
• Increased bronchial secretions and depressed respiratory muscles.
  
  
• Stimulated central nervous system, which in high doses may result in nausea, tremors or even convulsions.
  
  
• Increased glucose (blood sugar), but also less insulin – a chemical compound produced in the pancreas that helps the body process glucose. As a result, many smokers have slightly higher blood glucose (hyperglycemia).

Individuals have different sensitivities to nicotine and flush the drug out of their system at different speeds. This may account for variations of how often, and how much, tobacco users feel they need to smoke. Once the drug is out of a smoker’s system, that person begins to feel the effects of withdrawal (i.e., a “nicotine fit”). Studies have proven that after four hours without nicotine, withdrawal can interfere with work performance.

It is also possible to overdose on nicotine, which could produce symptoms such as:

• Mouth sores
• Muscle twitching
• Abdominal cramps
• Vomiting
• Headache
• Difficulty breathing
• Convulsions
• Collapse
• Coma

Effects of tar in tobacco smoke

Tar is a term used to describe the different carcinogens found in tobacco smoke that form a sticky, tar-like substance within the lungs. This substance irritates the lungs and respiratory system and is considered to be a major cause of lung cancer, bronchitis, emphysema and chronic obstructive pulmonary disease. So-called “low tar” cigarettes have shown to have little benefit, for those wishing to cut down on tar intake - many smokers compensate by taking longer, more intensive puffs. As a result, there has been a rise in cancers occurring in deeper areas of the lungs.

Effects of carbon monoxide in tobacco smoke

Carbon monoxide is a colorless, odorless, tasteless gas present in tobacco smoke. Other common sources are home furnaces and automobile engines. When tobacco smoke brings carbon monoxide into the body, it is absorbed into the bloodstream and begins to replace the oxygen normally carried by red blood cells to vital tissues and organs. Over time, the body’s organs cannot operate as efficiently because of the decrease in oxygen. Additionally, blood vessel linings are damaged, which contributes to atherosclerosis, a leading cause of heart attack and stroke.

Though lethal levels of carbon monoxide are not typically reached through smoking alone, smokers have a lower threshold for carbon monoxide poisoning due to the amount of the gas already present in their bodies. Carbon monoxide poisoning can lead to any of the following:

• Headache
• Nausea
• Dizziness
• Feeling tired or fatigued
• Rapid pulse
• Blurred vision
• Chest pain
• Convulsions
• Unconsciousness
• Death