What must inspiratory muscles do to overcome resistance in the lungs?

Correct answer: True

Subject adaptation refers to a decrease in chemoreceptor responsiveness after prolonged or chronic stimulation. Central and peripheral chemoreceptors, which normally detect changes in carbon dioxide, oxygen, and pH, may become less sensitive when exposed to persistently elevated or depressed levels of these stimuli. For example, patients with chronic hypercapnia, as seen in chronic obstructive pulmonary disease (COPD), often rely more on hypoxic drive for respiration because their central chemoreceptors adapt to high CO₂ levels. This physiological adaptation prevents overstimulation but also alters normal respiratory responses, confirming that decreased sensitivity due to chronic stimulation is an accurate description of subject adaptation.

A. Accessory muscles: Accessory muscles of respiration, including the sternocleidomastoid, scalene, and pectoralis minor, are recruited when increased ventilatory effort is needed, such as during exercise, respiratory distress, or lung diseases like COPD. They assist in elevating the thoracic cage, increasing lung expansion, and enhancing air movement into the lungs beyond what the primary muscles can achieve.

B. Vocal cords: Vocal cords are structures within the larynx that produce sound and regulate airflow through the glottis. They do not participate in the mechanics of breathing or provide supplemental respiratory power.

C. Bronchioles: Bronchioles are small airways that conduct air to the alveoli and regulate airflow through smooth muscle constriction or dilation. They are not muscles and do not contribute mechanical force to ventilation.

D. Primary muscles: The primary muscles of respiration, mainly the diaphragm and intercostal muscles, perform the bulk of normal, restful breathing. While essential for ventilation, they are supplemented by accessory muscles only when additional respiratory effort is required.