When a person inhales cigarette smoke, the nicotine in the smoke
is rapidly absorbed into the blood and starts affecting the brain
within 10 seconds. The result is the release of adrenaline, the
"fight or flight" hormone. Physically, adrenaline
increases a person's heart rate, blood pressure and restricts blood
flow to the heart muscle. When this occurs, the smoker experiences
rapid, shallow breathing and the feeling of a racing heartbeat.
Adrenaline also instructs the body to dump excess glucose into the
bloodstream.
Nicotine also inhibits the release of insulin from the pancreas,
a hormone that is responsible for removing excess sugar from a
person's blood. This leaves the smoker in a slightly hyperglycemic condition,
meaning he has more sugar in his blood than is normal. High blood
sugar acts as an appetite suppressant, which may be why smokers
think their cigarettes reduce hunger.
Nicotine activates the same reward pathways in the brain that
other drugs of abuse such as cocaine or amphetamines do, although
to a lesser degree. Research has shown that nicotine increases the
level of dopamine in the brain, a
neurotransmitter that is
responsible for feelings of pleasure and well-being. The acute
effects of nicotine wear off within minutes, so people must
continue dosing themselves frequently throughout the day to
maintain the pleasurable effects of nicotine and to prevent
withdrawal symptoms.
