Q1: Define Vital Capacity. What is its significance?
Answer: Vital Capacity (VC) is the maximum volume of air that a person can exhale after a forceful inhalation. It is calculated as IRV + TV + ERV.
Significance:
- Shows the functional efficiency of lungs
- Higher VC means better oxygen supply
- Athletes usually have higher VC due to regular training
Q2: State the volume of air remaining in the lungs after a normal expiration.
Answer: The air remaining in the lungs after normal breathing is called Functional Residual Capacity (FRC).
- Formula: FRC = ERV + RV
- Value: About 2300 mL
Key idea: This air prevents lung collapse and allows continuous gas exchange.
Q3: Why does diffusion of gases occur only in alveoli and not in other parts of the respiratory system?
Answer: Gas diffusion needs a surface that is thin, moist, and richly supplied with blood.
- Alveoli: Have extremely thin walls, large surface area, moisture, and dense capillaries → ideal for diffusion
- Other parts (trachea, bronchi): Thick walls with cartilage meant for air conduction, not gas exchange
Q4: What are the major transport mechanisms for carbon dioxide in blood?
Answer: Carbon dioxide is transported in three main forms:
- As bicarbonate ions (HCO₃⁻): ~70% (main form)
- As carbamino-haemoglobin: ~20–25%
- Dissolved in plasma: ~5–7%
Key point: Bicarbonate formation is helped by the enzyme carbonic anhydrase in RBCs.
Q5: Distinguish between Inspiratory Reserve Volume (IRV) and Expiratory Reserve Volume (ERV).
Answer:
| Feature | IRV | ERV |
|---|---|---|
| Meaning | Extra air inhaled forcibly | Extra air exhaled forcibly |
| Value | 2500–3000 mL | 1000–1100 mL |
| Associated with | Inspiration | Expiration |
Q6: What is the Oxygen Dissociation Curve? When does it shift to the right?
Answer: The Oxygen Dissociation Curve is a sigmoid (S-shaped) graph showing the relationship between percentage saturation of haemoglobin and pO₂.
Right shift (easy release of O₂) occurs when:
- pO₂ is low
- pCO₂ is high
- H⁺ concentration is high (low pH)
- Temperature is high
Student tip: Right shift = oxygen released to tissues easily
Q7: Match the respiratory organs with organisms.
Answer:
- Earthworm → Cutaneous respiration
- Insects → Tracheal system
- Fishes → Branchial respiration (gills)
- Birds/Mammals → Pulmonary respiration (lungs)
Q8: Explain the mechanism of inspiration.
Answer: Inspiration is an active process:
- Diaphragm contracts and flattens
- External intercostal muscles lift ribs and sternum
- Thoracic volume increases
- Intrapulmonary pressure decreases
- Air enters lungs due to pressure gradient
Q9: How is respiration regulated in humans?
Answer: Respiration is regulated mainly by the neural and chemical control systems:
- Respiratory rhythm centre (medulla): Sets basic rhythm
- Pneumotaxic centre (pons): Controls duration of inspiration
- Chemosensitive area: Detects CO₂ and H⁺
- Peripheral chemoreceptors: Located in carotid and aortic bodies
Q10: Why is carbon dioxide considered the main regulator of respiration?
Answer: Even a small increase in CO₂ strongly stimulates the respiratory centres through chemoreceptors. Oxygen levels have a much weaker effect.
Key point: CO₂ directly controls breathing rate by affecting blood pH.
Q11: What is the Bohr effect?
Answer: Bohr effect refers to the reduced affinity of haemoglobin for oxygen in the presence of high CO₂ and low pH, helping oxygen to be released in tissues.
Q12: What is the Haldane effect?
Answer: Haldane effect states that oxygenation of haemoglobin decreases its ability to carry CO₂, helping carbon dioxide to be released in lungs.
Q13: What is emphysema?
Answer: Emphysema is a chronic respiratory disorder in which alveolar walls are destroyed, reducing surface area for gas exchange. Smoking is the major cause.
---### Q14: What is asthma?
Answer: Asthma is an allergic respiratory disorder caused by narrowing of bronchioles due to inflammation, mucus secretion, and muscle spasm, leading to wheezing and breathlessness.
Q15: What are occupational respiratory disorders?
Answer: These disorders occur due to long-term exposure to industrial dust.
Examples:
- Silicosis: Silica dust
- Asbestosis: Asbestos fibres
They cause lung fibrosis and are usually irreversible.