Answer: Low arterial PO2 (hypoxia), high PCO2, and low pH.
- A Fluctuations in arterial blood pressure sensed via stretch receptors
- B Low arterial PO2 (hypoxia), high PCO2, and low pH
- C Core body temperature shifts relayed from the hypothalamus
- D Circulating blood glucose concentration via glucose-sensing neurons
Correct answer: B. Low arterial PO2 (hypoxia), high PCO2, and low pH
Explanation: Carotid body (and aortic bodies): peripheral chemoreceptors sensitive to low PO2 (<60 mmHg), high PCO2, and low pH. Signal brain stem respiratory centers to increase ventilation.
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.