I learned this today. Cigarettes are addictive because the nicotine they contain is a highly addictive chemical.
Nicotine is a naturally occurring chemical that is produced by plants. It is produced by many different types of plants: nightshade, tobacco, the coca plant, tomato, potato, eggplant, and green pepper. The concentrations differ depending on the plant. The plants have evolved to produce this chemical because it is a good insecticide. It discourages them from eating the plants because it kills them very quickly if they do.
There are basically two ways that nicotine enters our bodies: through our lungs or through our skin.
Through the lungs is probably the most common and comes from smoking cigarettes. When someone smokes, the smoke, containing nicotine and a whole pile of other chemicals, enters the lungs. From there it goes into the alveoli. These are tiny sacs that make up most of the area of the lungs. There are over 480 million of them. They are used by the body to oxygenate blood and to remove CO2 blood. The sacs are covered in tiny blood vessels. When they come close to the surface of the alveoli, they pick up oxygen molecules and release CO2 molecules. And they pick up nicotine. The nicotine enters the bloodstream.
The second most common way is through the skin and comes from nicotine patches. When you wear a nicotine patch, the nicotine is released, and it travels through the skin to the blood vessels, where it enters the bloodstream.
Once the nicotine is in the bloodstream it heads for the brain. It takes ten seconds for nicotine to enter the lungs and reach the brain. When the nicotine enters the brain, it binds to receptors that are meant for acetylcholine. Acetylcholine is a major neurotransmitter that provides signals for alertness, learning, and memory. It also tells the heart, blood vessels, and muscles to contract. Nicotine flows into the brain, and there is far more of it than acetylcholine, which is regulated, and it binds with all of the receptors giving a great sense of alertness, making the heart beat faster, increasing blood pressure, and making the muscles contract.
Nicotine also causes the brain to release dopamine. There is an area of the brain called the “reward pathway”. It is an area that is activated by natural rewards such as food, water, and sex. When the pathway is activated, it makes us want more of whatever is activating it, which is an extremely important evolutionary advantage. We want our brain to make us want more of the things we need. The problem comes when the brain makes us want more of the things we don’t need.
The nicotine makes the brain release dopamine, which binds to the dopamine receptors and makes us feel good. Our brain associates this feeling with the nicotine (or rather the action of smoking) and wants us to do more of it to get that feeling again.
Nicotine is broken down by the body extremely quickly, so the rush from the cigarette doesn’t last long and the nicotine addict has to quickly find another cigarette.
As people take in more nicotine, the brain makes more acetylcholine receptors to deal with it. This creates a circle because it now takes more nicotine to make the same reaction, so the person smokes more, taking in more nicotine, which keeps the cycle going. This is called tolerance. The next step after this is dependence. The body becomes so used to the feeling of the nicotine that it becomes unable to cope without it. And the next step is addiction.
So, we become addicted to nicotine because it binds to acetylcholine receptors in our brain and gives us a sense of alertness and feeling awake and alive. It also causes the brain to release dopamine which makes us feel good. Our brain associates all of these feelings with pleasure and tries to make us find more of it. However, when we take in more nicotine, the brain adapts to it and demands even more. And that cycle continues, which is why we become addicted to nicotine. And this is what I learned today.
Sources
https://en.wikipedia.org/wiki/Nicotine
https://www.swedish.org/classes-and-resources/smoking-cessation/nicotine-dependence-how-it-happens
https://en.wikipedia.org/wiki/History_of_tobacco
https://www.quit.org.au/articles/nicotine-addiction-explained/