Web Bit 37-1: How Does Tobacco Smoke Damage the Cardiovascular System?
By Allan Tobin and Jennie Dusheck
The three most dangerous substances in tobacco smoke are nicotine, carbon monoxide, and tar. Tar, a brown, oily substance, ruins the lungs, while nicotine and carbon monoxide work together to damage the heart and arteries.
Nicotine is a stimulant with a broad range of effects. By mimicking the neurotransmitter acetylcholine, it increases the heart rate and constricts the blood vessels, causing the blood pressure to increase. Nicotine also stimulates the release of antidiuretic hormone (vasopressin), a hormone that causes the kidneys to retain water, which can further raise blood pressure. In addition, nicotine increases the tendency of the blood platelets to form clots. High blood pressure and abnormal clots are two factors that can trigger a heart attack or stroke.
Nicotine contributes to hardening of the arteries, or atherosclerosis, a major cause of heart attacks and strokes. By increasing blood pressure, nicotine causes damage to the arteries, which then become inflamed and scarred. Finally, nicotine increases levels of cholesterol in the blood, which, in response to the inflammation, forms deposits on the arterial walls. These deposits further narrow the arteries and increase the likelihood that a blood clot will plug an artery and cause a heart attack or stroke.
Smokers say nicotine makes them feel good. It relaxes the muscles and increases alpha waves, brain waves that characterize a pleasant, relaxed state. If you want to know what it feels like to increase alpha waves in the brain, sit down in front of the television for a few minutes. While nicotine maintains the cigarette habit and raises blood pressure, carbon monoxide interferes with the body's ability to supply oxygen to the cells of the body. Carbon monoxide is an odorless and toxic gas. Cigarettes are not the only source of carbon monoxide. Exhaust from automobiles and furnaces, for example, also release carbon monoxide. Government regulations outlaw levels higher than 10 parts per million (ppm) in homes or at work. Yet, cigarette smoke contains about 1600 ppm carbon monoxide.
In the blood, carbon monoxide binds to hemoglobin and displaces oxygen. Inhaling carbon monoxide reduces oxygen supplies to every cell in the body. The heart and the brain, however, are affected most. Oxygen deprivation in the brain impairs judgment, vision, and the ability to distinguish sounds. Oxygen deprivation in the heart reduces its ability to pump blood. But the high blood pressure induced by nicotine means that the heart needs to work harder than usual. The result can be muscle strain and long-term damage to the heart.