Explain how chemicals present in cigarette smoke are able to enter the body and reach the brain

When you smoke a cigarette, the components; e. g. nicotine and carbon monoxide enter the lungs and are absorbed into the bloodstream. They are carried by the Red Blood Cells to the blood-brain barrier, here, nicotine binds to nicotinic acetylcholine receptors (nAChRs), resulting to a cascade that results to release of dopamine (good-feeling neurotransmitter).