Human Physiology
Key Concepts
| # | Concept | Explanation |
|---|---|---|
| 1 | Blood Groups | ABO system: A, B, AB, O based on antigens; Rh+/- decides compatibility. |
| 2 | Haemoglobin | Iron-rich pigment in RBCs; 1 Hb carries 4 O₂ molecules; normal adult Hb = 12-16 g/dL. |
| 3 | Digestive Enzymes | Ptyalin (mouth) → Pepsin (stomach) → Trypsin (small intestine); each acts at optimum pH. |
| 4 | Neuron | Dendrite → Cell body → Axon → Synapse; impulse travels 120 m/s in myelinated fibres. |
| 5 | Hormones | Chemical messengers by endocrine glands; travel blood → target organ; slow & long-lasting. |
| 6 | Heart Valves | Tricuspid (R-side), Bicuspid (L-side), Semilunar (aorta/pulmonary); prevent back-flow. |
| 7 | Alveoli | 300 million sacs; total surface 70 m²; 1-cell thick for gas exchange. |
| 8 | Nephron | Functional unit of kidney; filters 180 L/day but excretes only 1-2 L urine. |
15 Practice MCQs
1. The pH of human blood is approximately
A) 6.8 B) 7.0 C) 7.4 D) 8.0 Answer: C) 7.4 **Trick**: “7.4 = All is fine” (remember normal body pH). **Tag**: Acid–base balance / Blood2. Which enzyme is present in saliva?
A) Pepsin B) Ptyalin C) Lipase D) Renin Answer: B) Ptyalin **Trick**: “Pty- for Pie (starch)” – Ptyalin breaks starch. **Tag**: Digestion3. The largest artery in the human body is
A) Pulmonary artery B) Carotid C) Aorta D) Femoral Answer: C) Aorta **Trick**: “Aorta = Airport” – biggest highway. **Tag**: Circulation4. Insulin is secreted by
A) Liver B) Pancreas β-cells C) Thyroid D) Adrenal Answer: B) Pancreas β-cells **Trick**: “β = Bed-time” (lowers sugar before rest). **Tag**: Hormones5. Oxygen mainly combines with which part of haemoglobin?
A) Iron B) Copper C) Magnesium D) Zinc Answer: A) Iron **Trick**: “Fe = Ferrum = Fix O₂”. **Tag**: Respiration6. Normal duration of cardiac cycle is
A) 0.8 s B) 1.2 s C) 1.5 s D) 2.0 s Answer: A) 0.8 s **Trick**: 72 beats/min ⇒ 60/72 ≈ 0.8 s. **Tag**: Heart7. Which part of the brain controls heartbeat & breathing?
A) Cerebrum B) Cerebellum C) Medulla D) Hypothalamus Answer: C) Medulla **Trick**: “Medulla = Manditory life buttons”. **Tag**: Nervous system8. The hormone that regulates sleep–wake cycle is
A) Cortisol B) Melatonin C) ADH D) Thyroxine Answer: B) Melatonin **Trick**: “Melatonin = Midnight hormone” from Pineal. **Tag**: Hormones9. Which blood cells are largest in size?
A) RBC B) Platelets C) Monocytes D) Neutrophils Answer: C) Monocytes **Trick**: “Mono = Monster size”. **Tag**: Blood cells10. Bile is stored in
A) Liver B) Pancreas C) Gall bladder D) Duodenum Answer: C) Gall bladder **Trick**: “Gall = Garage for bile”. **Tag**: Digestion11. The functional unit of kidney is
A) Neuron B) Nephron C) Alveolus D) Sarcomere Answer: B) Nephron **Trick**: “Nephron = Never fails to filter”. **Tag**: Excretion12. Which vitamin is essential for blood clotting?
A) A B) C C) K D) D Answer: C) K **Trick**: “K = Koagulation (German spelling)”. **Tag**: Vitamins13. During inspiration, diaphragm becomes
A) Flattened B) Dome-shaped C) Relaxed D) Passive Answer: A) Flattened **Trick**: “In-Flat-ion”. **Tag**: Respiration14. Which chamber of heart receives oxygenated blood?
A) Right atrium B) Left atrium C) Right ventricle D) Pulmonary artery Answer: B) Left atrium **Trick**: “LOVE = Left = Oxygenated”. **Tag**: Heart15. The pigment giving urine yellow colour is
A) Bilirubin B) Urochrome C) Haemoglobin D) Melanin Answer: B) Urochrome **Trick**: “Uro = Urine chrome = colour”. **Tag**: ExcretionSpeed Tricks
| Situation | Shortcut | Example |
|---|---|---|
| Remember 4 blood types | “A-B-AB-O, Rh is + or −” | O− = universal donor; AB+ = universal recipient. |
| Enzyme optimum pH | “Pie-Try-Pe” (Ptyalin 6.8, Trypsin 8, Pepsin 2)” | Saliva neutral, stomach acidic, intestine alkaline. |
| Heart valve order | “Tri before Bi, Semi at exit” | Tricuspid → Pulmonary valve → Mitral (Bicuspid) → Aortic valve. |
| Endocrine vs Exocrine | “Endo = Enter blood” | Pancreas is both; insulin (endo), pancreatic juice (exo). |
| Glomerular filtration rate | “180 L/day ≈ 125 mL/min” | Quick recall for MCQs asking GFR. |
Quick Revision
| Point | Detail |
|---|---|
| 1 | RBCs lack nucleus & mitochondria → max space for Hb. |
| 2 | Platelets life = 7–10 days; RBC = 120 days. |
| 3 | SA-node: pacemaker; generates 72 impulses/min. |
| 4 | CO₂ transported mainly as bicarbonate (70%) in plasma. |
| 5 | Pepsin secreted as inactive pepsinogen by chief cells. |
| 6 | ADH (vasopressin) increases water reabsorption in nephron. |
| 7 | Thyroxine needs iodine; deficiency → goitre. |
| 8 | Alveolar air has pO₂ ≈ 104 mmHg, pCO₂ ≈ 40 mmHg. |
| 9 | Right kidney sits slightly lower due to liver space. |
| 10 | CSF: 150 mL volume, replaced 3–4 times daily; cushions brain. |
BETA
