9 - Manaia Breathing

Q1. What do the diaphragm and intercostal muscles do during inspiration/Inhale?

A1. Diaphragm contracts and pulls → external intercostal muscles pull ribs up and out → thoracic cavity volume increases → pressure inside lungs drops → air flows in.

Q2. If Manaia’s blood CO₂ rises above the set point, can she consciously control her breathing for long? Why?

A2. No → rising CO₂ stimulates chemoreceptors → brainstem takes over → involuntary breathing occurs.

Q3. How is breathing rate regulated by homeostatic feedback when Manaia is not consciously controlling it?

A3. CO₂ rises → chemoreceptors detect change → medulla/pons increase breathing rate → diaphragm & intercostals contract faster → more CO₂ exhaled → balance restored.

Q4. How do mucous membranes and the mucociliary elevator protect the respiratory tract?

A4. Mucous membranes trap dust & pathogens → cilia sweep mucus upwards by mucociliary elevator → mucus swallowed or coughed out → lungs protected.

Q5. How does Manaia’s skin help regulate temperature during labour?

A5. Labour raises body heat → skin blood vessels vasodilate → more blood flows to skin → sweat released → sweat evaporates → temperature homeostasis maintained.

Q6. How are oxygen and carbon dioxide exchanged in the lungs?

A6. O₂ high in alveoli and low in blood → O₂ diffuses into Capillaries → CO₂ high in blood and low in alveoli → CO₂ diffuses into alveoli → gases exchanged by diffusion.

*Gases always move from high pressure gradient to low pressure.

Q7. What are two ways carbon dioxide is transported in the blood?

A7.

• CO₂ carried as bicarbonate in plasma.

• CO₂ carried attached to haemoglobin.

Q8. Why can Manaia’s heart rate increase but her blood pressure remain normal?

A8. BP = SV × HR × TPR →

Labour stress activates sympathetic NS → HR increases, cardiac output rises → arterioles vasodilate, lowering TPR → ↑HR balanced by ↓TPR → BP stays normal.