The rate and depth of breathing are regulated mainly by the level of
Correct answer: D. carbon dioxide in the blood, monitored by the medulla oblongata
- A. oxygen in the alveoli
- B. glucose in the blood
- C. nitrogen in the blood
- D. carbon dioxide in the blood, monitored by the medulla oblongata
Explanation
Chemoreceptors in the medulla and in the great arteries respond to the fall in pH that a rise in carbon dioxide produces, and the respiratory centre then increases the rate and depth of breathing until the excess is blown off. Oxygen level acts only as a weak backup stimulus and matters mainly at high altitude. This is why holding the breath becomes unbearable from the build up of carbon dioxide, not from the lack of oxygen.
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About Gaseous Exchange in Lungs
Gaseous exchange in the lungs occurs across the thin, moist alveolar and capillary surfaces, where oxygen and carbon dioxide diffuse down partial pressure gradients. The topic covers alveolar adaptations, ventilation, the role of haemoglobin in oxygen transport, carbon dioxide carriage, and the difference between external gas exchange and cellular respiration.
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