Tobacco (Nicotine)

The Physiological Effects of Smoking Nicotine

A.   Short-Term Effects:

1.    Nicotine constricts terminal bronchioles
decreases airflow into and out of the lungs

2.    CO in smoke binds to hemoglobin
reducing its O₂-carrying capability

3.    Irritants in smoke cause increased mucosa secretions
results in swelling of mucosal lining
impedes airflow into and out of the lungs

4.    Furthermore, irritants in smoke inhibit the movement of cilia of the respiratory system
a. Excess fluids and foreign debris are not easily removed
b. Adds further to the difficulty of breathing

B.   Long-Term Effects of Smoking

1.    Destruction of Elastic Fibers in the Lungs

2.    Smoking acts as a persistent stressor

3.    Increased mucus is secreted

4.    Cilia become ineffective

5.    Mucus remains trapped in the bronchial tubes

6.    "Smoker’s Cough"

a.     Irritation slowly destroys the alveoli

b.     Replaced with thick inelastic connective tissue

c.     Damaged alveoli are destroyed by the immune system

II. The effects of one cigarette

A.   If a person has not smoked for twelve hours and then has a cigarette, the following things happen

B.   Carbon monoxide levels in the lungs increase. This gas is quickly absorbed into the blood, reducing its capacity to carry oxygen. The inhalation of carbon monoxide via passive smoking has the same effect.

C.   The changes brought about by carbon monoxide mean that more effort must be made to achieve the same physical results as a non-smoker. In particular, the heart must work harder for the same effect, especially when doing rigorous exercise.

D.   Studies have shown that the levels of carbon monoxide in the blood of a 20-cigarette-a-day smoker can impair vision, perception of time and coordination.

E.    Nicotine from tobacco smoke reaches the brain and muscle tissue soon after being inhaled.

F.    When nicotine is present a number of changes occur:

1.    The heart rate increases.

2.    This can be measured as an increase in pulse rate.

3.    Basically nicotine has the ability to stimulate neurons in the brain.

4.    Depending on where in the brain these neurons are, a euphoric sensation can be experienced by the smoker, leading to a physical need for nicotine.

5.    According to one study: Many smokers continue to smoke because nicotine helps them to regulate mood.

6.    The nicotine intake leads promptly and noticeably to pleasant, desired psychotropic effects.

7.    In the event of physical dependence, the occurrence of withdrawal symptoms results in renewed nicotine intake.

8.    Psychological and physiological dependence could be very different among smokers and this has important implications on the motivation for smoking cessation

III. How does nicotine deliver its effect?

A.   Nicotine can act as both a stimulant and a sedative.

B.   Immediately after exposure to nicotine, there is a "kick" caused in part by the drug's stimulation of the adrenal glands and resulting discharge of epinephrine (adrenaline).

C.   The rush of adrenaline stimulates the body and causes a sudden release of glucose as well as an increase in blood pressure, respiration, and heart rate.

D.   Nicotine also suppresses insulin output from the pancreas, which means that smokers are always slightly hyperglycemic.

E.    In addition, nicotine indirectly causes a release of dopamine in the brain regions that control pleasure and motivation.

F.    This reaction is similar to that seen with other drugs of abuse - such as cocaine and heroin - and it is thought to underlie the pleasurable sensations experienced by many smokers.

G.   In contrast, nicotine can also exert a sedative effect, depending on the level of the smoker's nervous system arousal and the dose of nicotine taken.

III. What happens when nicotine is taken for long periods of time?

A.   Chronic exposure to nicotine results in addiction.

B.   Research is just beginning to document all of the neurological changes that accompany the development and maintenance of nicotine addiction.

C.   The behavioral consequences of these changes are well documented, however.

D.   Greater than 90 percent of those smokers who try to quit without seeking treatment fail, with most relapsing within a week.

E.    Recent research has shown in fine detail how nicotine acts on the brain to produce a number of behavioral effects.

F.    Of primary importance to its addictive nature are findings that nicotine activates the brain circuitry that regulates feelings of pleasure, the so-called reward pathways.

G.   A key brain chemical involved in mediating the desire to consume drugs is the neurotransmitter dopamine, and research has shown that nicotine increases the levels of dopamine in the reward circuits.

H.   Nicotine's pharmacokinetic properties have been found also to enhance its abuse potential.

I.     Cigarette smoking produces a rapid distribution of nicotine to the brain, with drug levels peaking within 10 seconds of inhalation.

J.     The acute effects of nicotine dissipate in a few minutes, causing the smoker to continue dosing frequently throughout the day to maintain the drug's pleasurable effects and prevent withdrawal.

K.   What people frequently do not realize is that the cigarette is a very efficient and highly engineered drug-delivery system.

1.    By inhaling, the smoker can get nicotine to the brain very rapidly with every puff.

2.    A typical smoker will take 10 puffs on a cigarette over a period of 5 minutes that the cigarette is lit.

3.    Thus, a person who smokes about 1-1/2 packs (30 cigarettes) daily, gets 300 "hits" of nicotine to the brain each day.

L.    These factors contribute considerably to nicotine's highly addictive nature.

1.    Addiction- dependence on a substance to the point that stopping is very difficult and causes severe physical and mental reactions.

2.    Pattern of compulsive drug use characterized by a continued craving for a substance and the need to use the substance for effects other than pain relief.

M.  Research shows that nicotine, like other addictive drugs, affects the mesolimbic system--the part, of the brain that produces "feel good" chemicals.

N.   One recent study zeroed in on a specific brain protein, called beta 2 subunit, that is essential to nicotine addiction.

O.   Without this protein in their brains, lab mice don't experience nicotine's pleasurable sensations.

P.    Result: They don't crave or get addicted to the drug. Scientists hope such studies can lead to better methods for treating nicotine addiction.

IV. Smoke signals

A.   Not every smoker is addicted to nicotine, About one in 10 is an occasional smoker, who can pass on a cigarette for days without suffering from withdrawal symptoms, like wrenching headaches or intense cravings.

B.   But the vast majority of smokers become hooked on nicotine.

C.   The key may lie in brain chemistry.

1.    "When you smoke nicotine or any drug, for that matter, it reaches the brain in about eight seconds," explains Dr. Stephen Heishman, a NIDA researcher in Baltimore, Maryland.

2.    In the brain, nicotine stimulates the release of dopamine, a chemical or neurotransmitter that allows communication between nerve cells

3.    Dopamine transmits pleasure signals when you eat chocolate or receive a hug, for example.

4.    By releasing a cascade of dopamine in the brain, nicotine gives smokers that pleasurable feeling that makes them want more--and more.

V. What a Drag!

A.   Nicotine addiction is not instantaneous. "Addiction takes around two to three years--from the time a person first tries a cigarette to the point where he or she is smoking on a daily basis," Dr. Heishman says.

B.   In fact, the first drag often makes a new smoker dizzy and nauseous, thanks to nicotine's adverse effects.

C.   Few people realize that pure nicotine is actually quite deadly.

D.   Nicotine is the active ingredient in some insecticides. A couple of drops (about 60 milligrams) of pure nicotine would kill you.

E.    For every cigarette a person smokes, he or she inhales about 1 to 3 mg of nicotine.

F.    Fortunately, the body quickly breaks down nicotine to keep it from building up to a fatal dose.

G.   After repeated exposure to nicotine, your body gets used to the drug.

H.   The brain creates more receptors, the parts of a nerve cell to which nicotine and neurotransmitters bind.

I.     This process is part of why smokers get addicted. "With more receptors, you need more of a drug to occupy those receptors," Dr. Heishman says. That's what makes quitting so hard.

VI. Up in smoke

A.   Strangely enough, nicotine is not what makes smoking so harmful.

B.   The real villain is the cigarette itself, which pumps more than 4,000 chemicals into yom' body, about 200 of which are poisonous.

C.   The damage that's done to the heart and lungs is primarily due to tars, carcinogens (cancer-causing chemicals), and carbon monoxide in smoke.

D.   Compared to a cigarette's other hazards, nicotine is fairly safe.

E.    This is why the Food and Drug Administration approved nicotine replacement therapy--nicotine gum and patches--to treat smokers.

F.    Both gum and patches deliver nicotine to the brain, but at a much slower rate than cigarettes.

G.   In patches, small doses of nicotine are released through the skin over a given period of time.

H.   While both alternatives can satisfy nicotine craving, they're less likely to lead to addiction.

VII. An alternative treatment for nicotine addiction

A.   ImmuLogic, a Massachusetts company, plans to test an anti-smoking vaccine on volunteers--smokers trying to kick the habit.

B.   The vaccine's antibodies (substances that destroy foreign matter in the body) seek out and neutralize nicotine before it reaches the brain's receptors.

C.   Smokers no longer get a "nicotine hit," so smoking loses its appeal.

D.   Ultimately, the best treatment for quitting cigarettes may combine drugs that combat nicotine craving, therapy that helps smokers control the way they respond to cravings. Best prevention: Don't even start!

VIII. Smoking Statistics

A.   Statistics show smoking's deadly truths

B.   Smoking is the most wide spread addiction.

3. Statistics show that in 90 years there have been 1.1 billion smokers in the world, among them 47% men and 12% women out of the whole population.
4. Only in China there are 300 million smokers, 90% men and 10% women.
5. In the developed countries 42% of all men and 24% of all women smoke, whereas in developing countries approximately 48% of men and 7% of women, because smoking has spread there only recently.
6. Prevalence among men depends on geographic and also social situation.
7. Most male smokers come from west pacific regions, where more than 60% of men smoke.
8. In China, for example, which is the biggest country of this region, about 61% of men are smokers.
9. Per year smokers smoke about 6 million tons of tobacco in different ways (cigarettes, cigars, pipe tobacco...).
10. Consumption of tobacco increases every day, especially in poor countries, whereas in more developed countries it decreases, which is a result of people being more conscious of the harm caused by tobacco.
11. 430,000 annual deaths attributable to cigarette smoking - United States, 1990-1994
12. The Centers for Disease Control says smoking is the single greatest preventable cause of illness and premature death in the United States.
13. People who smoke are at increased risk of heart disease, cancer and other smoking-related illnesses that contribute to more than 420,000 deaths a year.
14. Medical costs for smokers are $50 billion annually, plus an additional $47 billion for indirect expenses, such as time lost from work and disability.
15. Smoking represents additional health threats to women, including cervical cancer, reproductive and pregnancy complications, and early menopause.
16. If they smoke and use oral contraceptives, women are at increased risk of coronary heart disease.
17. Some evidence also suggests that women may have a harder time quitting than men, and recent data indicates that the message to avoid smoking has been less successful in reaching young women than young men.
18. Government statistics show there is a larger percentage of male smokers (32 percent) than female (27 percent), but the gender gap has narrowed dramatically over the past 25 years.
19. While the percentage of male smokers has dropped by nearly 40 percent from its peak, the percentage of female smokers has dropped only 18 percent since its peak in 1966.
20. And, in some age groups (late teens and early 20s), the percentage of female smokers exceeds that of male smokers.
21. The Centers for Disease Control estimates, if current trends continue, that by the mid 1990's there will be more women than men who smoke, both proportionally and in actual numbers of smokers.

References

ChemFinder.Com Search Form. http://chemfinder.camsoft.com/. 2000. ChemFinder.Com Search Form.

Drug Facts - Nicotine. http://www.alapubhealth.org/inform/drugweb/pages/nicotin.htm. 2001. Alabama Department of Public Health

Nicotine. http://wso.williams.edu/orgs/peerh/drugs/nicotine.html. 2001. Drugs and Alcohol.

Re: Why is smoking habit-forming? http://www.madsci.org/posts/archives/aug98/899398293.Ns.r.html. 2000.Madsci.

Science World - Hooked On Nicotine. http://www.findarticles.com/m1590/7_55/53461443/p1/article.jhtml. 2000. Science World.

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