Answer: Medullary rhythm/respiratory centre.
- A Medullary rhythm/respiratory centre
- B Carotid body chemoreceptors
- C Aortic body chemoreceptors
- D Pneumotaxic centre in the pons
Correct answer: A. Medullary rhythm/respiratory centre
Explanation: The medullary respiratory rhythm centre generates the basic rhythm of breathing, while the pneumotaxic centre in the pons can moderate the duration and depth of breaths.
The S-shaped (sigmoid) curve reflects cooperative binding between Hb's four O₂ sites; the Bohr effect shifts the whole curve to the right under conditions found in actively respiring tissue (more CO₂, more acid, more heat), making haemoglobin release oxygen more readily exactly where it's needed.
Concept context
The mechanics of breathing, lung volumes, gas transport in blood, the Bohr effect, and respiratory regulation.