What exactly does nicotine do that makes it addictive?

I have heard many times that nicotine is the most addictive drug on the plantet and hardest to get off of......I knew a woman once that was addicted to heroin....she kicked that habit, she could NOT kick the nicotine addiction.....even with rehab's help....could someone please tell me what nicotine does to the body that makes the body become addicted to it?....I have smoked cigarettes off and on for years now...but until recently I have never felt like I was hooked...now I am starting to "crave" them....I hate that.....please help....any info appreciated.....

There is plenty of accurate scientific information available on the effects of nicotine. If you read it you will hear that it affects acetylcholine receptors and dopamine levels. Basically, it causes your brain to send you chemicals that "reward" you. Everytime you get nicotine into your bloodstream, it is like your brain is saying "good job!", even though you probably don't feel euphoric at all...please, please, learn the lesson from your friend and just stop smoking entirely while you still can!

like any chemical, you can get addicted to it. i certainly am. but personally, i think cigarettes is much more psychological.. they are cheap, relativesly speaking, it involves using your hands and mouth, and you usually get hooked up because it looks cool as a teenager or it just goes with drinking at bars. im sick of it but havent found anything to totally get me to stop.

This might explain it...

"Nicotine is highly addictive. Nicotine provides an almost immediate "kick" because it causes a discharge of epinephrine from the adrenal cortex. This stimulates the central nervous system, and other endocrine glands, which causes a sudden release of glucose. Stimulation is then followed by depression and fatigue, leading the smoker to seek more nicotine..."