The Physiological Effects of Nicotine

What makes nicotine so dangerous and so addictive? Again, the answer begins in the brain. When a person takes a puff on a cigarette, the nicotine is pulled into the lungs and absorbed directly into the bloodstream. Within eight to 10 seconds, nicotine has penetrated the brain and begins to cause its characteristic “rush.”

Nicotine and the Brain

A logical question is, how could the brain be affected so quickly? Part of the answer has to do with the shape of the nicotine molecule. Its shape is similar to a natural neurotransmitter in the brain called acetylcholine. Because the shape of nicotine is so close to that of acetylcholine, it can fit into the receptor sites on brain cells that actually belong to acetylcholine.

One might think of nicotine as an interloper in the brain's messenger system. Once nicotine has connected with the acetylcholine receptors, a person's heart rate, blood pressure, and respirations increase as does the release of glucose into the bloodstream. The person smoking may experience these changes and interpret them as increased mental alertness.


Depression among smokers is three times more common than with nonsmokers. Thus it is thought that many individuals use nicotine as a way to self-medicate their mood disorder. Individuals who are treated with medication and therapy for their depression are more likely to successfully quit smoking and remain smoke-free.

Another way that nicotine affects the brain is through the now familiar dopamine pleasure pathway. Nicotine stimulates the release of large amounts of dopamine, the neurotransmitter that causes intense feelings of pleasure. You may recall from reading about methamphetamines that once dopamine has completed its prescribed function of transmitting messages from neuron to neuron, in a normally functioning brain it gets recycled. For some unknown reason, components of cigarette smoke block the reabsorption of dopamine. It remains in the space between the neurons called the synaptic gap, contributing to the intense feelings of pleasure that a person addicted to nicotine experiences.

Beta-endorphins are another type of neurotransmitter that have the ability to enhance moods. Nicotine stimulates the release of beta-endorphins as well as dopamine. In addition to these significant effects of nicotine on one's brain, it also has been found to interrupt the flow of oxygen to the brain, especially the right hemisphere. Nicotine also elevates the body's levels of cortisol, which is a hormone involved in relieving stress by arousing the sympathetic nervous system.


Research has shown that adolescents who smoke are fifteen times more likely than nonsmoking peers to experience anxiety, depression, and panic attacks. One possible explanation is that nicotine may damage blood vessels to the brain while also decreasing oxygenation to the lungs. This is yet one more reason why it is so important to educate young people about nicotine use.

One can readily see that nicotine affects the brain on many levels. However, these effects come and go quickly. Recall that the drug reaches the brain within eight to 10 seconds. Within 40 minutes, half of the effects caused by nicotine are over. This process is somewhat slower for a person who uses smokeless tobacco or who smokes cigars or pipes. The result is that, before long, someone addicted to nicotine is needing another dose of the drug either to achieve the desired effects or to prevent withdrawal symptoms.

Over a period of time, the brain begins to make changes in order to adjust to the effects of the drug, particularly the increased production of dopamine. For example, the brain cuts down on its normal production of dopamine and reduces the number of certain brain cell receptors. Again, adjustments must be made to maintain homeostasis, or balance, in the brain's functioning. The addicted person must now consume more of the drug to stimulate the release of more dopamine just to feel “normal.”

Systemic Effects of Nicotine

While much attention has been given to the effects of nicotine on the brain, nicotine has harmful effects on every vital organ in the body. In the lungs, nicotine is a primary contributor to lung cancer, emphysema, pneumonia, and chronic bronchitis. Nicotine has been connected to leukemia and cataracts. It has been strongly associated with cancers of the esophagus, larynx, throat, mouth, bladder, pancreas, liver, kidneys, cervix, stomach, colon, and rectum.

What is nicotine poisoning?

Nicotine poisoning occurs when someone is exposed to high levels of nicotine. It only takes one drop of pure nicotine to cause death. Symptoms of nicotine poisoning include vomiting, tremors, convulsions, and even death. One way this may occur is through exposure to high doses of insecticides that contain nicotine. It does not occur from smoking too much.

The heart and circulatory systems demonstrate the harmful effects of nicotine through strokes, heart attacks, vascular diseases, and aneurysms. In terms of the reproductive system, nicotine increases the risks for infertility and miscarriages in women and impotence and infertility in men. Infants are at risk for low birth weight, premature delivery, and lung problems when their mothers use nicotine during their pregnancies.

Smoking tends to deaden one's sense of taste and smell, which can contribute to poor appetite and a loss of enjoyment while eating. The immune system is affected and individuals addicted to nicotine seem to be more prone to infectious illnesses such as colds and the flu compared to non-addicted people. Smoking tends to dry and irritate one's skin cells, promoting wrinkles and giving one the appearance of premature aging.

Cigarette smoking can also cause a yellowing of one's teeth, fingers, and fingernails. Smokeless tobacco products can cause gum disease, bad breath, and stained teeth. They can also destroy the bone sockets surrounding one's teeth and thus cause tooth loss. The number of harmful effects from nicotine can definitely be overwhelming and frightening. There is hope, and treatment options will be discussed soon. But first, consider the psychological aspects of nicotine addiction.

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