Happened upon this today while searching the effects of nicotine. It gives more in-depth information than the EX Plan does. Below is a sample of the material in this link: http://science.howstuffworks.com/nicotine.htm
Effects of Nicotine
Ever wonder why smokers crave a cigarette when they're in a bad mood or in a stressful situation? It's because nicotine may help people feel calmer, causing temporary feelings of relaxation as well as reducing stress, anxiety and even pain [source: World Health Organization].
In spite of that relaxation, though, nicotine actually increases physical stress; its effects are considered a bit of a paradox. It perks up the central nervous system, but depending on the dosage some smokers find nicotine also acts as a sedative. Some studies, though, suggest it may just be the ritual of smoking that induces a calming effect, because nicotine is actually considered a stimulant, not a depressant.
Nicotine in the Body
Just 10 seconds after a cigarette smoker inhales, nicotine is absorbed through the skin and the mucosal linings in the nose, mouth and lungs, and travels through the bloodstream to the brain. It stimulates adrenal glands to produce epinephrine, a hormone and neurotransmitter you also know as adrenaline. This increases heart rate and blood pressure while constricting blood vessels; it also stimulates the production of dopamine, a neurotransmitter that controls the brain's pleasure center. Inhaling nicotine gives the most immediate effects, and that's not a coincidence; it's because your lungs are lined with millions of tiny air sacs called alveoli. Alveoli provide an enormous surface area -- more than 40 times the surface area of your skin -- making it the most efficient way to get nicotine into the bloodstream [source: Richardson]. Nicotine only stays in the human body for a few hours; it has a half-life of about an hour or two, meaning that six hours after smoking a cigarette, only about 0.031 milligram of the 1 milligram of nicotine you inhaled remains [source: Hukkanen, Benowitz].
Nicotine can also be absorbed through your gastrointestinal tract and your skin -- this is how smokeless tobacco products such as chewing tobacco, skin patches and gum deliver their nicotine fix.
.... Nicotine also increases the level of other neurotransmitters and chemicals that modulate how your brain works. For example, your brain makes more endorphins in response to nicotine. Endorphins are small proteins that are often called the body's natural painkiller. It turns out that the chemical structure of endorphins is very similar to that of heavy-duty synthetic painkillers like morphine. Endorphins can lead to feelings of euphoria, and may explain nicotine's psychoactive and rewarding effects.
.... You don't need to inhale nicotine to become addicted. Smokeless tobacco products are also addictive; an average-sized dip resting between your cheek and lip for about 30 minutes will give you the same nicotine fix as if you smoked three cigarettes [source: BeTobaccoFree.gov].