Multiple choice

In mammals, the process of ventilation is normally controlled by the autonomic nervous system. Which among the following statements does NOT characterise ventilation in humans?

  1. Pregnancy tends to increase ventilation.

  2. The tone of respiratory muscle is modulated by muscle spindles via a reflex arc.

  3. Ventilatory rate is usually controlled and determined by blood levels of oxygen as determined by metabolic rate.

  4. During moderate exercise, ventilation increases in proportion to metabolic production of carbon dioxide.

  5. Afferent neurons from the carotid bodies and aortic bodies are via the glossopharyngeal nerve.
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C Correct answer
Explanation

Ventilatory rate (minute volume) is strictly controlled and determined primarily by blood levels of carbon dioxide as determined by metabolic rate. Blood levels of oxygen become important in hypoxia. These levels are sensed by chemoreceptors in the medulla oblongata for pH, and the carotid and aortic bodies for oxygen and carbon dioxide.

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