During the "fight or flight" response, stimulation from the sympathetic division of the autonomic nervous system causes the bronchial tubes to dilate, allowing more air through the lungs.

The lower respiratory tract is lined with tiny hair-like structures known as cilia, which move in a coordinated wave-like motion to help move debris upward and out of the lungs. Once the debris reaches the larger bronchial tubes it can stimulate the cough reflex, which is designed to expel debris from the respiratory tract.

	The tiny delicate cilia are killed by tobacco smoke; and as a result, smokers have few if any cilia remaining in their lungs. Because of this, and the constant irritation of smoke, smokers are much more susceptible to all sorts of respiratory problems. Smoking is also the primary cause of lung cancer, is a major contributor to all sorts of circulatory problems including heart disease and stroke, and is responsible for nearly all cases of emphysema. Smoking also contributes to stomach ulcers, harms unborn babies, and increases the risk of osteoporosis. And second-hand smoke also harms nonsmokers, including children. The children of smokers suffer from many more respiratory problems and ear infections than those of non-smokers. Smoking has justifiably earned the reputation of being the largest preventable cause of death and disease.

Debris is moved out of the lungs with the aid of . . .

A. the cough reflex
B. smoking
C. cilia
D. Both A and C.

(Select the best answer and click on the "Continue" button.)

       

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