How nicotine acts in our body after consumption of Tobacco or smoking ciggars? Explain machenism.?
Answers:
As nicotine enters the body, it is distributed quickly through the bloodstream and can cross the blood-brain barrier. On average it takes about seven seconds for the substance to reach the brain when inhaled. The half life of nicotine in the body is around two hours.
Nicotine acts on the nicotinic acetylcholine receptors. In small concentrations it increases the activity of these receptors, among other things leading to an increased flow of adrenaline (epinephrine), a stimulating hormone. The release of adrenaline causes an increase in heart rate, blood pressure and respiration, as well as higher glucose levels in the blood.
The sympathetic nervous system, acting via splanchnic nerves to the adrenal medulla, stimulates the release of epinephrine. Acetylcholine released by preganglionic sympathetic fibers of these nerves acts on nicotinic acetylcholine receptors, causing cell depolarization and an influx of calcium through voltage-gated calcium channels. Calcium triggers the exocytosis of chromaffin granules and thus the release of epinephrine (and norepinephrine) into the bloodstream.
In high doses, nicotine will cause a blocking of the nicotinic acetylcholine receptor, which is the reason for its toxicity and its effectiveness as an insecticide.
In addition, nicotine increases dopamine levels in the reward circuits of the brain. Studies have shown that smoking tobacco inhibits monoamine oxidase (MAO), an enzyme responsible for breaking down monoaminergic neurotransmitters such as dopamine, in the brain. It is currently believed that nicotine by itself does not inhibit the production of monoamine oxidase (MAO), but that other ingredients in inhaled tobacco smoke are believed to be responsible for this activity. In this way, it generates feelings of pleasure, similar to that caused by cocaine and heroin, thus causing the addiction associated with the need to sustain high dopamine levels.
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