Nicotine is a naturally occurring alkaloid found in tobacco plants. Nicotine has a physiologic effect because it binds to receptors on the neuromuscular system. Nicotine affects the skeletal, smooth and cardiac muscles, which can result in acute and chronic muscular dysfunctions such as a decrease in appetite, paralysis and asphyxiation.
Smooth Muscles of the Gastrointestinal Tracts
Nicotine exposure causes acute action on the smooth muscles of the gastrointestinal tract, resulting in a loss of appetite. Nicotine is also believed to affect the smooth muscles of the colon, altering the gut motility. This results in an alteration of the rate at which food and digested material move through the gastrointestinal tract. Smoking cigarettes or any other tobacco product containing nicotine, causes the release of nitric oxide at various sites in the gastrointestinal tract. Nitric oxide relaxes the smooth muscles of the gastrointestinal tract and reduces muscular tone and activity.
Nicotine acts a stimulant binding to nicotinic receptors at the postganglionic neurons, notes McGraw Hill Higher Education. Nicotine binds to these receptors and causes a continual stimulation of the heart muscles, resulting in either an increased or decreased heart rate depending on its action on the parasympathetic or sympathetic nervous system. The opposing stimulation caused by nicotine causes the rhythm of the heart to become less regular. According to the International Programme on Chemical Safety, nicotine causes constriction of the peripheral blood vessels along with tachycardia, or a rapid heart beat, as well as an increase in blood pressure. Nicotine can also cause cardiac arrhythmia, arterial fibrillation and cardiac standstill as a result of its continual stimulation of the cardiac muscles.
Nicotine travels through the bloodstream and reaches the brain within 10 to 19 seconds. Nicotine acts on nicotinic receptors in the brain and muscles. According to Elmhurst College, nicotine causes muscle twitching and muscle weakness. Nicotine also acts on nicotinic receptors in the respiratory muscles causing paralysis as well as vasodilation in the skeletal muscles. Nicotine's vasodilation of skeletal muscles results in increased blood flow and well as a relaxing effect on the skeletal muscles of the body.