| Term | Definition | NEET Relevance |
|---|---|---|
| Tidal Volume (TV) | Volume of air moved in/out during a single normal breath (~500 mL) | Base value for capacity calculations |
| Inspiratory Reserve Volume (IRV) | Extra air forcibly inhaled beyond TV (2500–3000 mL) | Largest single lung volume |
| Expiratory Reserve Volume (ERV) | Extra air forcibly exhaled beyond normal expiration (1000–1100 mL) | Part of VC, FRC, EC |
| Residual Volume (RV) | Air remaining in lungs after maximum forced expiration (1100–1200 mL); cannot be voluntarily expelled | Cannot be measured by spirometry |
| Vital Capacity (VC) | TV + IRV + ERV; max voluntary air movement (~3500–4600 mL) | Excludes RV; most clinically relevant capacity |
| Total Lung Capacity (TLC) | VC + RV; all air in lungs after deepest inspiration (~5000–6000 mL) | Contains RV; cannot be fully measured by spirometry |
| Functional Residual Capacity (FRC) | ERV + RV; air remaining after normal expiration (~2100–2300 mL) | Different from RV; NEET trap |
| Diffusion membrane | 3-layered barrier (alveolar epithelium + basement membrane + capillary endothelium) | 3 layers — must know all |
| Oxyhaemoglobin | O2 bound to Fe2+ in haem group of Hb; carries 97% of blood O2 | Primary O2 transport form |
| Carbaminohaemoglobin | CO2 bound to amino groups of globin chains of Hb; carries 23% of blood CO2 | CO2 binds protein, not haem |
| Bohr effect | Right shift of O2–Hb curve due to increased CO2, H+, temperature, 2,3-BPG | Right shift = lower affinity = more O2 to tissues |
| Haldane effect | Oxygenation of Hb reduces its ability to carry CO2 and H+ | Complementary to Bohr; promotes CO2 release at lungs |
| Chloride shift | HCO3– exits RBC; Cl– enters RBC to maintain electrical neutrality | Also called Hamburger's phenomenon |
| Carbonic anhydrase | Enzyme in RBCs catalysing CO2 + H2O ⇌ H2CO3 | Critical for 70% CO2 transport as HCO3– |
| Pneumotaxic centre | Regulatory centre in pons that inhibits inspiration and limits its duration | Located in pons; limits inspiration |
| Respiratory rhythmicity centre | Primary breathing pacemaker in medulla oblongata | Sets basic breathing rhythm |
| Peripheral chemoreceptors | Carotid and aortic bodies detecting pO2, pCO2, and H+ | Both locations must be known |
| Intrapleural pressure | Slightly negative pressure in pleural space maintaining lung inflation | Negative = keeps lungs inflated |
| Emphysema | Chronic destruction of alveolar walls, loss of elastic recoil, air trapping | Barrel chest; increased RV |
| Silicosis | Lung fibrosis from chronic silica dust inhalation | Occupational disease; irreversible |
Part of HP-02 — Breathing & Exchange of Gases
Key Definitions Glossary — Breathing and Gas Exchange
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