True/False Misconceptions — Breathing and Gas Exchange — Notes

18 True/False Statements with Corrections

Statement	True/False	Correction (if False)
1. Residual volume remains after a normal quiet expiration.	FALSE	RV remains after MAXIMUM FORCED expiration. After normal expiration = FRC.
2. Vital Capacity = TV + IRV + ERV + RV.	FALSE	VC = TV + IRV + ERV only. Adding RV gives TLC, not VC.
3. The primary form of CO2 transport in blood is bicarbonate ions.	TRUE	70% as HCO3– — correct.
4. Quiet (normal) expiration requires contraction of internal intercostals.	FALSE	Quiet expiration is PASSIVE (elastic recoil). Internal intercostals = forced expiration.
5. A right shift of the O2–Hb curve means haemoglobin has a higher affinity for O2.	FALSE	Right shift = LOWER O2 affinity → more O2 released to tissues.
6. The pneumotaxic centre in the pons initiates the breathing rhythm.	FALSE	The MEDULLARY RHYTHMICITY centre initiates rhythm. Pons pneumotaxic = limits inspiration.
7. During the chloride shift, HCO3– moves INTO RBCs from plasma.	FALSE	HCO3– moves OUT of RBCs; Cl– moves INTO RBCs.
8. The right lung has 2 lobes; the left lung has 3 lobes.	FALSE	Right = 3 lobes; Left = 2 lobes (cardiac notch).
9. CO2 is transported primarily as carbaminohaemoglobin.	FALSE	CO2 = 70% HCO3–, 23% carbaminoHb, 7% dissolved.
10. The alveolar diffusion membrane has 3 layers.	TRUE	Alveolar epithelium + basement membrane + capillary endothelium.
11. Gas exchange in alveoli occurs by active transport.	FALSE	Gas exchange is by SIMPLE DIFFUSION along partial pressure gradients.
12. Alveolar pO2 is approximately 104 mmHg.	TRUE	Correct value to memorise.
13. CO2 binds to the iron atom in the haem group to form carbaminohaemoglobin.	FALSE	CO2 binds to amino groups (–NH2) of the GLOBIN chains, not haem iron. O2 binds Fe2+.
14. Carbonic anhydrase is found primarily in plasma.	FALSE	Carbonic anhydrase is primarily in RED BLOOD CELLS.
15. The left lung is smaller to accommodate the cardiac notch.	TRUE	Left lung has 2 lobes due to the cardiac notch.
16. Emphysema causes an increase in residual volume.	TRUE	Air trapping from loss of elastic recoil increases RV in emphysema.
17. CO2 diffuses more slowly than O2 because its partial pressure gradient is smaller.	FALSE	CO2 diffuses MORE RAPIDLY than O2 per unit pressure difference due to its ~20× higher solubility.
18. Peripheral chemoreceptors in the carotid bodies respond only to changes in pO2.	FALSE	Carotid bodies detect pO2, pCO2, AND H+ concentration.