pulmonary circulation following inhalation from which it passes through the left side of the heart and into the cerebral circulation. It rapidly crosses the blood-brain barrier and binds to specific receptors in various parts of the brain. Stimulation of receptors by nicotine results in the activation of a number of neurohumoral pathways leading to release of acetylcholine, norepinephrine, dopamine, serotonin, vasopressin and various hormones. Nicotine causes the release of the substance b-endorphin, an endogenous peptide that also binds to opiate receptors. This indicates a link between addiction to opiates, such as morphine and heroin, and addiction to nicotine.Nicotine affects nearly all components of the endocrine and neuroendocrine systems, including catecholamines, serotonin, corticosteroids and pituitary hormones.Some of these endocrine effects are mediated by actions of nicotine on brain neurotransmitter systems. In addition, nicotine causes skeletal muscle relaxation and has cardiovascular effects.Nicotine is a powerful substance in controlling brain function. It interacts with specific receptors in brain tissue, and initiates metabolic and electrical activity in the brain. The individual cells within the brain, the neurons, release a whole array of chemical signals in communication with one another . The most common chemical signal that is used in the brain is a transmitter called glutamate, which stimulates the brain. The production of glutamate requires the brain chemical acetylcholine, and studies have shown that nicotine has similar affects to acetylcholine on the receptors in the brain due to their common dimensions. *How nicotine acts depends on factors including the amount of nicotine in the body, the time passed since the last cigarette and stress level of the smoker. Nicotine has a stimulating effect, but intake of larger doses can lead to paralysis, vasoconstriction and tachycardia. Nicotine mimics a chemical...
