Nicotine is an organic compound that is found naturally in the tobacco plant. It is composed of carbon, nitrogen, hydrogen and oxygen and belongs to a group of compounds called alkaloids. Plants usually produce these types of chemical poisons so that animals are deterred from eating them. In high concentrations nicotine acts as a nerve poison and it is used in insecticides. However, in small amounts, nicotine is a stimulant that enhances brain activity and concentration and improves cognitive processing as well as a person's memory. On the downside, nicotine increases blood pressure and heart rate, causes you to breathe faster and less deeply and it constricts the arteries.