Nicotine is one of the most powerful of all known drugs. Two or three drops placed on your tongue would be enough to kill you. And, for that matter, the amount of nicotine in a cigar would be fatal if it were administered as an injection in a single swift dose.
The way nicotine affects the organs of the body — every one of them, at that — seems to stem from its action at certain key points in the brain and the whole nervous system. And one of the most intriguing things about nicotine‘s effects is that they are often paradoxical. The effect of one particular dose at one particular spot can be quite different from that of another dose at another spot. Also, a low, short dose of nicotine may stimulate whereas a long-lasting high dose may depress or even paralyse.
Nicotine‘s Effects on the Brain and Nervous System
Nicotine appears to have a stimulating effect on the brain. This is something which many smokers say they experience, and it is also indicated by very “hyper” patterns in the electrical recordings used to measure brain waves. But the effect is likely to be brief at best, and to be followed by a feeling of sedation, especially if you smoke a good deal. Another thing that can happen is that one part of the brain may be stimulated while another part is depressed: the release of the neurotransmitter acetylcholine from the cortex, or outer layer, of the brain contributes to this paradoxical effect.
Nicotine also affects other parts of the central nervous system. According to some of the latest research, there may even be specific receptor sites for nicotine. Receptors are little grab points on the membrane of a cell that a particular chemical can latch on to, thereby causing a certain effect on the body. If indeed nicotine receptors do exist, then it may be possible to block them, just as is already being done with receptors for certain other drugs. This, incidentally, brings up a fascinating question: if it does become possible to block nicotine receptors, could this ever serve as a means to help smokers stop and stay off cigarettes?
Nicotine‘s Effect on the Heart and Blood Vessels
Nicotine makes your heart beat faster. In increases the amount of blood that your heart pumps out with each beat, and the speed and force with which it does this. Another effect is the boost it gives your blood pressure. The mechanism underlying all this is the release of epinephrine, or adrenalin, and other catecholamines (stimulating substances) from the heart tissues and also from the adrenal glands.
Nicotine also reduces the blood flow reaching the surface of the body, and this makes the skin temperature drop. A single cigarette contains enough nicotine to slow the blood flow in your fingers by over 40 per cent, and people who smoke heavily often have cold hands and feet.
The cardiovascular system reacts much more noticeably to nicotine after a period of abstinence. Effects can last for as long as an hour, all told.
Nicotine‘s Effects on the Stomach and Intestines
Smoking has been shown to stimulate the output of saliva, lessen hunger pangs for as much as an hour, reduce the secretion of gastric juice in the stomach, and sometimes delay the emptying of the stomach, too. It also tends to increase bowel activity; in fact, temporary constipation is one of the common withdrawal symptoms.
Nicotine‘s Effects on Behavior and Learning
Studies with animals suggest that nicotine, in small doses, helps learning processes, probably through the release of norepinephrine — another of the catecholamines — in the brain. But in larger doses nicotine has the opposite effect, through the counteraction of acetylcholine. Among human beings, smoking does seem to help addicted smokers concentrate and deal with stressful situations. It does not, however, enable them to perform better than people who do not smoke at all.
Nicotine and Tranquillisation
One of the best examples of nicotine‘s paradoxical effects is the way in which a small dose seems to stimulate a person psychologically while a larger one relaxes. Quite apart from all this, nicotine does have a specifically relaxing physical effect on the skeletal muscles of the body.
Nicotine‘s Effects on Weight
Through its stimulating effect, nicotine mobilises the release of fatty acids into the bloodstream; as a result, smokers do not use the calories of the food they eat as efficiently as non-smokers do. It may be because of this metabolic squandering, and a shift to greater efficiency in calorie metabolism which takes place when people stop smoking, that ex-smokers so often complain of gaining weight after they have stopped.
Interestingly, another alkaloid, caffeine, seems to have the same metabolic effect as nicotine does on calories. So for some people, coffee may be a good thing while giving up smoking, although there are others who find it too closely associated with cigarettes.
