Monday, June 30, 2008

What Nicotine does to the Brain

The reason why people smoke is to experience the effects that nicotine has on the brain. Cigarettes are a nicotine delivery system. Inhaling smoke into the lungs is the fastest way to get nicotine to the brain. The lungs have a large surface area and the capillary walls are very accessible. Up to 90% of the nicotine in mainstream smoke is absorbed and it enters the arterial system and moves fairly directly to the brain, arriving within 7 to 10 seconds. The concentration of nicotine can be three times higher than if the nicotine was injected into veins of the arm because through the venous system, first the blood is pumped to the heart, then to the lungs, back to the heart before finally going to the brain. No product reaches the brain as fast as smoking. Inhaling smoke gives higher, faster, and shorter surges of nicotine to the brain when compared to the nicotine replacement products.

Nicotine then needs to pass through the blood-brain barrier. Ammonia is added to tobacco to increase the PH of the cigarette because a higher PH allows nicotine to cross this barrier easier. Once in the brain nicotine binds to specific areas called nicotinic acetylcholine receptors. Smokers have more of these receptors than non-smokers. Smoking may increase the number of receptors or smoking may allow the receptors to live longer.

Nicotine affects the different parts of the brain in different ways depending on the dosage. Each cigarette is like getting 10 injections of nicotine. Smokers unconsciously regulate the amount of nicotine by either inhaling deeper or smoking more of the cigarette. Sometimes the smoker may use a cigarette to relax, at other times as a stimulant. Menthol cigarettes cool the smoke which causes the smoker to inhale deeper.

When nicotine occupies the receptors in the pleasure pathway, dopamine is released which causes pleasurable sensations (positive reinforcement) and removes unpleasant sensations of pain, anxiety or feelings of illness (negative reinforcement). When the brain has an increase in dopamine, it may be that this increases the attention that the individual places on external activities. These external activities become paired with the pleasurable sensations and become triggers themselves for smokers to light up. The brain becomes conditioned so that when a trigger happens, such as answering the telephone, the brain lights up and expects nicotine to occupy the receptors which the smoker experiences as “cravings”. So any event that a smoker does habitually can be paired with smoking and become a trigger to light up. The brain becomes conditioned to these pleasurable sensations and will “crave” nicotine when faced with these triggers even if they have just finished a cigarette.

Individuals smoke for a combination of both positive and negative reinforcement. When an individual starts smoking it is usually for the pleasurable effects and at some point the individual continues to smoke to avoid the unpleasant effects of withdrawals. Individuals with depression, Attention-Deficit Hyper Activity, and other mental conditions, will start smoking to relieve negative sensations, a form of self-medication. The pattern starts with the individual smoking irregularly but with each cigarette, the nicotine changes the structure of the brain until the individual increases the number of cigarettes and the frequency until addiction sets in, which can occur within three to six months of the first cigarette.

The other area of the brain that nicotine affects is the locus ceruleus which controls vigilance, arousal, concentration and stress reactions. It is also responsible for an individual’s response to stress, anxiety and panic, which may explain why smokers use tobacco in times of high stress and as a way of coping with negative emotions.

The brain structure is changed by smoking. Nicotine floods the brain with dopamine yet the body is constantly seeking balance or homeostasis. The receptor that normally accepts the dopamine is changed to lessen the effect of this flood of dopamine. This change can last five to ten years.

During the quitting process, the smoker may experience withdrawals which are physical symptoms when a drug has not been used for a period of time. Withdrawal symptoms from nicotine includes irritability, frustration, anger, anxiety, depression, difficulty concentrating, restlessness, decreased heart rate, a change in appetite, either hunger or an increase in appetite, a change in sleep habits, either insomnia or inability to fall asleep. The body is also recovering from the effects of smoking and the smoker may experience an increase in coughing, tightness in the throat, dry mouth, dizziness, lightheadedness, headaches, fatigue, difficulty in concentrating and confusion. Medications can help with these symptoms.

Cravings are not the same as withdrawals. Cravings or powerful urges to smoke happen when the brain is conditioned to want nicotine either through positive or negative reinforcement. The brain is shouting, “Where is my nicotine?” Over time cravings become less intense and less frequent. Medications can help with these cravings. Relapse occurs when a smoker will reintroduce nicotine which immediately lights up the receptors in the smoker’s brain. Often only one cigarette is all it takes for the individual to relapse back to full time smoking again because of the strong effect nicotine has on the brain. The brain has memory of how it felt with nicotine and re-addiction can happen within one day when nicotine is re-introduced. The brain has a memory and with the reintroduction of nicotine, the chemical state of the brain matches up with memories of how the individual was when he or she was addicted.

Besides nicotine there are estimated to be 4000 to 5000 chemicals in tobacco smoke. About 400 are either poisonous, cancer causing, or cancer promoting. It is unknown exactly what ingredients are in cigarettes because while the tobacco companies are required to give a list of their ingredients to the government, this information is not released to the public because it is considered a "trade secret". Additives are used to alter the pH level to make nicotine more accessible to the body and to keep the cigarettes burning longer. Nicotine delivery systems are the least regulated consumer product, yet one of the most deadly. There are a few of these chemicals:

Nicotine: A poisonous alkaloid that is the chief active principle of tobacco and is used as an insecticide.
Tar: A particulate matter made up of dozens of compounds. Some are toxic, some are cancer-causing agents. Tar cools inside the lungs, forming a sticky mass and damaging lung tissue. A quart of tar goes through the lungs of a pack a day smoker every year.
Carbon Monoxide: Deprives oxygen from the red blood cells. It stays in the blood hemoglobin for up to six hours after exposure. Is related to heart attacks and strokes. Affects non-smokers. Binds to red blood cells in the lungs 230 times faster than oxygen.
Hydrogen Cyanide: Poison used in the gas chamber. EPA standards indicate that 10 parts per million as safe however cigarette smoke produces an average 1600 parts per million.
Arsenic: A metallic substance, poisonous to all life. The human body can build up a tolerance to arsenic.
Benzene: A poison that interferes with cellular metabolism.
Cadmium: A metal which accumulates in the lungs and stays there. Has an adverse effect on the protective immune devices of the body. Used in batteries.
Ammonia: This chemical is added to tobacco to increase the pH level to make it easier for nicotine to cross the blood brain barrier. Used as a household chemical.
Acetone: Used as nail polish remover.
Toluene: Industrial solvent.
Formaldehyde: Embalming fluid.
Methanol: Rocket fuel.
Naphthalene: Mothball Chemical.
Nitrobenzene: Gasoline additive.
Mercury: Found in thermometers.
Nitrous oxide: Disinfectant.
Stearic acid: Candle wax
Butane: Cigarette lighter fuel.
Vinyl Chloride: Component of PVC pipe.
DDT: Insecticide banned by most Western industrialized nations.
Hexamine: Barbecue lighter

No comments: