Answer: Medulla oblongata, in the brainstem.
- A Medulla oblongata, in the brainstem
- B Cerebrum, in the frontal region
- C Cerebellum, behind the brainstem
- D Spinal cord, near the cervical region
Correct answer: A. Medulla oblongata, in the brainstem
Explanation: The respiratory rhythm centre in the medulla oblongata generates the basic rhythm of breathing; a pneumotaxic centre in the pons fine-tunes it.
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.