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Control of respiration · Physiology

Which of the following describes the primary mechanism by which central chemoreceptors are stimulated during a rise in arterial PCO2?

  1. Direct binding of CO2 molecules to the chemoreceptor cell membrane surface
  2. Diffusion of arterial H+ ions directly across the intact blood-brain barrier
  3. CO2 diffuses into the CSF, where it forms H+ ions that stimulate the receptors
  4. Carotid bodies detect the CO2 and signal the central receptors via the vagus nerve
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Correct answer: CO2 diffuses into the CSF, where it forms H+ ions that stimulate the receptors

While central chemoreceptors are highly sensitive to H+, these ions cannot easily cross the blood-brain barrier. Instead, CO2 diffuses into the CSF and brain interstitial fluid, where it reacts with water to form H+ ions that directly stimulate the receptors.

Difficulty: Medium Question 21 of 40

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