Biology Human Body - Quick Revision
Biology Human Body - Quick Revision
Key Points (One-Liners)
- Largest organ: Skin (≈1.8 m²).
- RBCs live 120 days; no nucleus, no mitochondria.
- Universal donor blood: O-negative; universal recipient: AB-positive.
- pH of human blood: 7.35–7.45 (slightly alkaline).
- Normal BP: 120/80 mmHg; systolic = heart contracts, diastolic = relaxes.
- Heart sound “LUB” = AV valves close; “DUB” = semilunar valves close.
- Alveoli total surface area ≈ 70 m² (tennis-court size).
- Bile is stored in gall bladder; produced by liver; no enzyme, emulsifies fat.
- Pepsin works best at pH 1.5–2.5 in stomach.
- Nephron is the functional unit of kidney; ~1 million per kidney.
- Neuron longest cell; synapse uses neuro-transmitters.
- Insulin lowers blood glucose; glucagon raises it (both from pancreas).
- Growth hormone from pituitary; hypothalamus is “CEO of hormones”.
- Fertilisation in fallopian tube (ampulla); implantation in uterus.
- Placenta secretes hCG—pregnancy test marker.
- Antibodies are made by B-lymphocytes; IgG crosses placenta.
- Vaccines give active artificial immunity; antitoxin gives passive.
- Normal haemoglobin: Male 14–16 g/dL, Female 12–14 g/dL.
- SA node = “pacemaker”; generates 72 beats/min.
- CSF (cerebro-spinal fluid) cushions brain & spinal cord.
| Formula/Rule |
Application |
| Cardiac output = Stroke volume × Heart rate (CO = SV × HR) |
Calculate blood pumped per minute (≈5 L). |
| Vital capacity = IRV + TV + ERV |
Max air exhaled after max inhalation. |
| BMI = mass(kg) ÷ height²(m²) |
Obesity cut-off ≥25 kg/m². |
| GFR ≈ 125 ml/min (glomerular filtration rate) |
Kidney function screening. |
| Minute ventilation = TV × Respiratory rate |
Alveolar ventilation per minute. |
| O₂ carrying capacity ≈ 1.34 ml O₂ per g Hb |
Anaemia severity estimate. |
| Basal metabolic rate ∝ Body surface area |
Energy need at rest. |
| Refractive power (eye) = 1/focal length(m) |
Dioptre calculation. |
| Hardy-Weinberg: p² + 2pq + q² = 1 |
Carrier frequency in genetics (rarely asked) |
Memory Tricks
- Cranial nerves: “On Old Olympus’ Towering Top….” (I-Olfactory, II-Optic, III-Oculomotor…).
- Endocrine “FLAT PEG”: FSH, LH, ACTH, TSH, Prolactin, Endorphins, Growth hormone—all from anterior pituitary.
- Enzymes of gut: “LIPS-T” – Lipase (fat), Pepsin (protein), Salivary amylase, Trypsin.
- Heart valves: “Try Pulling My Aorta” – Tricuspid, Pulmonary, Mitral, Aortic (order of blood flow).
- Carbohydrate absorption site: “DJ” – Duodenum & Jejunum (remember like Disc Jockey).
Common Mistakes
| Mistake |
Correct Approach |
| Saying bile digests fat |
Bile only emulsifies; lipase digests. |
| Confusing ureter (tube) with urethra |
Ureter kidney→bladder; urethra bladder→outside. |
| Calling platelets “blood cells” |
They are fragments of megakaryocytes, not true cells. |
| Stating insulin is produced by liver |
It’s pancreatic β-cells; liver stores glycogen. |
| Reversing systolic/diastolic values |
Always write 120/80—top number is systolic. |
Last Minute Tips
- Glance at labelled heart & nephron diagrams—RRB loves image-based MCQs.
- Remember ±10 % of normal values (e.g., Hb, BP, RBC count) for “which is abnormal?” questions.
- First 3 minutes: attempt all human-body questions—they’re usually fact-based & quick.
- If two options look identical, pick the one with units (mL, pH, etc.)—often the precise answer.
- Don’t overthink negative marking—if 90 % sure, attempt; else skip.
Quick Practice (5 MCQs)
1. Which blood vessel carries oxygenated blood from lungs to heart?
Pulmonary vein
2. The enzyme pepsin is secreted by — and acts in —.
Gastric chief cells; stomach
3. Normal GFR in a healthy adult is approximately
125 mL/min
4. Which part of the brain controls breathing rhythm?
Medulla oblongata
5. A person with blood group AB can safely receive blood from
All groups (A, B, AB, O)
BETA
