Question

Many runners find that smoking cigarettes decreases their speed and endurance. This finding is due to all of the following effects of nicotine EXCEPT A. constriction of the terminal bronchioles of the lungs. B. increase in surfactant secretion by type II alveolar epithelial cells. C. swelling of the epithelial linings. D. paralysis of the cilia on the surfaces of respiratory epithelial cells.

Short answer

B

Step-by-step solution

- Understand the Effects of Nicotine

Review the common physiological impacts of nicotine on the body, especially concerning the respiratory system. Nicotine often causes constriction of air passages, swelling in epithelial linings, and damage to cilia functionality.

- Analyze Each Option

Examine each option to determine which effects are associated with nicotine and which are not. Pay attention to the physiological functions of the lungs and consider how nicotine would impact each function.

- Evaluate Option A

Nicotine constricts the terminal bronchioles of the lungs, making it harder to breathe. This option is consistent with known effects.

- Evaluate Option B

Nicotine does not increase surfactant secretion by type II alveolar epithelial cells. Surfactant is a substance that helps keep the lungs inflated, and there is no evidence that nicotine affects its secretion.

- Evaluate Option C

Nicotine causes swelling of the epithelial linings. This option is also consistent with the smoking-related changes in respiratory tissues.

- Evaluate Option D

Nicotine can paralyze the cilia on the surfaces of respiratory epithelial cells, preventing them from removing mucus and debris effectively. This option aligns with known effects.

- Identify the Exception

Determine that Option B is the only effect not supported by nicotine's known impacts on the respiratory system.

Key concepts

bronchiole constriction

Nicotine has a significant impact on the respiratory system by causing constriction of the terminal bronchioles. This narrowing of air passages makes breathing more difficult. Terminal bronchioles are the small airways in the lungs that lead to the air sacs where gas exchange occurs. When these passages constrict, less oxygen can reach the lungs, and it becomes harder to expel carbon dioxide. This results in decreased oxygen supply to the body, making physical activities like running much more challenging. This response is part of the body's natural defense mechanism to harmful substances, but it also severely impacts respiratory efficiency and overall endurance.

epithelial swelling

Nicotine exposure leads to swelling of the epithelial linings of the respiratory tract. The epithelium is a thin layer of tissue that lines the airways and aids in protecting the respiratory system. Swelling occurs as a reaction to the irritation and inflammation caused by nicotine. This inflammation can restrict airflow and cause discomfort during breathing. Swollen epithelial cells can also produce more mucus, further obstructing the air passages. For athletes, this means reduced lung capacity and less efficient oxygen exchange, ultimately leading to poorer performance and endurance.

cilia paralysis

Cilia are tiny hair-like structures on the surface of respiratory epithelial cells. They move rhythmically to clear mucus and debris from the respiratory tract. Nicotine can paralyze these cilia, preventing them from functioning correctly. This paralysis means that mucus and harmful particles remain in the airways longer, leading to congestion and increased risk of infections. In the context of physical exertion, such as running, an impaired ability to clear out mucus results in increased difficulty in breathing and can reduce stamina. Healthy cilia are critical for maintaining clear airways and ensuring efficient respiratory function.

surfactant secretion

Surfactant is a substance secreted by type II alveolar epithelial cells in the lungs. It reduces surface tension, keeping the alveoli — the tiny air sacs in the lungs — open, allowing for efficient gas exchange. However, nicotine does not actually increase surfactant secretion. In fact, there is no substantial evidence to suggest that nicotine affects surfactant levels directly. This is crucial because proper surfactant levels are needed to prevent the alveoli from collapsing, ensuring that the lungs remain inflated and functional. Misconceptions about nicotine's effects on surfactant can lead to misunderstandings about how smoking impacts lung health and physical performance.