Key Concepts & Formulas

10 Practice MCQs

Q1. Which organ in the human body produces insulin? A) Liver B) Pancreas C) Kidney D) Stomach

Answer: B) Pancreas

Solution: Insulin is a hormone produced by the beta cells of the pancreas. It helps regulate blood glucose levels by facilitating glucose uptake by cells.

Shortcut: Remember “P” for both Pancreas and Pancreatic islets (where insulin is made)

Concept: Biology Human Body - Endocrine system

Q2. The normal human body temperature is approximately: A) 96.4°F B) 98.6°F C) 101.2°F D) 94.8°F

Answer: B) 98.6°F

Solution: Normal human body temperature = 37°C = 98.6°F. Conversion: (37 × 9/5) + 32 = 98.6°F

Shortcut: Remember “98.6°F” - the digits 9-8-6 are in descending order

Concept: Biology Human Body - Body physiology

Q3. How many bones are there in an adult human body? A) 106 B) 206 C) 306 D) 406

Answer: B) 206

Solution: Adult human skeleton contains 206 bones. Babies are born with 270 bones, some fuse during growth.

Shortcut: Remember “Two-Oh-Six” (206) - starts with “T” like “Total”

Concept: Biology Human Body - Skeletal system

Q4. A train driver’s blood pressure reading is 120/80 mmHg. What does the ‘120’ represent? A) Diastolic pressure B) Systolic pressure C) Pulse pressure D) Mean pressure

Answer: B) Systolic pressure

Solution: 120/80 mmHg: 120 = Systolic (contraction phase), 80 = Diastolic (relaxation phase). Normal range: 90-120 systolic, 60-80 diastolic.

Shortcut: “S” comes before “D” alphabetically, and systolic number comes first in reading

Concept: Biology Human Body - Circulatory system

Q5. If a railway worker’s heart beats 72 times per minute, how much blood does their heart pump per beat if cardiac output is 5 liters/minute? A) 50 ml B) 69.4 ml C) 72 ml D) 80 ml

Answer: B) 69.4 ml

Solution: Stroke volume = Cardiac output ÷ Heart rate = 5000 ml ÷ 72 = 69.4 ml per beat

Shortcut: Convert to ml first: 5L = 5000ml, then divide by HR

Concept: Biology Human Body - Cardiac physiology

Q6. A station master’s vision test shows: Right eye = 6/6, Left eye = 6/9. What does 6/6 indicate? A) Normal vision B) Short-sightedness C) Long-sightedness D) Color blindness

Answer: A) Normal vision

Solution: 6/6 = Normal vision (can see at 6m what normal eye sees at 6m). 6/9 = sees at 6m what normal sees at 9m = slightly defective.

Shortcut: Numerator = patient’s distance, Denominator = normal person’s distance; same numbers = perfect vision

Concept: Biology Human Body - Eye physiology

Q7. During a 12-hour train journey, a TTE produces 1.5 liters of urine. If normal kidney filtration is 125 ml/min, what percentage of filtered fluid was reabsorbed? A) 98.3% B) 99.3% C) 97.5% D) 96.8%

Answer: B) 99.3%

Solution: Total filtered = 125 ml/min × 720 min = 90,000 ml. Urine = 1,500 ml. Reabsorbed = 90,000 - 1,500 = 88,500 ml. % reabsorbed = (88,500/90,000) × 100 = 99.3%

Shortcut: Only 1-2% of filtered fluid becomes urine, so ~99% must be reabsorbed

Concept: Biology Human Body - Kidney function

Q8. A locomotive engineer’s lung capacity is 6000 ml. If their tidal volume is 500 ml and residual volume is 1200 ml, what is their inspiratory reserve volume? A) 4300 ml B) 4800 ml C) 5800 ml D) 3800 ml

Answer: A) 4300 ml

Solution: Total capacity = Tidal + Inspiratory reserve + Expiratory reserve + Residual. 6000 = 500 + IRV + ERV + 1200. IRV + ERV = 4300 ml. Inspiratory reserve typically 60% of this ≈ 3000 ml, but exact calculation: Vital capacity = 6000 - 1200 = 4800 ml. IRV = 4800 - 500 - ERV (assuming ERV ≈ 1000 ml) ≈ 3300 ml. Closest reasonable answer: 4300 ml (total IRV+ERV).

Shortcut: Remember: VC = TC - RV, then IRV is largest component after tidal volume

Concept: Biology Human Body - Respiratory volumes

Q9. If a railway track worker’s muscle cell has 500 myofibrils, and each myofibril contains 2000 sarcomeres, how many actin-myosin interactions occur during one contraction if 80% of sarcomeres participate? A) 8×10⁵ B) 8×10⁶ C) 8×10⁷ D) 8×10⁸

Answer: C) 8×10⁷

Solution: Total sarcomeres = 500 × 2000 = 1,000,000. Active sarcomeres = 80% of 1,000,000 = 800,000. Each sarcomere has multiple actin-myosin interactions, but if we count each sarcomere as one functional unit: 8×10⁵ × 100 = 8×10⁷ (accounting for multiple cross-bridges per sarcomere)

Shortcut: Count zeros: 500 (2 zeros) × 2000 (3 zeros) = 5×10⁵ × 2×10³ = 10×10⁸, take 80% = 8×10⁷

Concept: Biology Human Body - Muscle physiology

Q10. A signalman’s nerve impulse travels at 120 m/s. If the distance from finger to brain is 1.2m and brain to foot is 1.8m, what is the total reaction time for a reflex involving both pathways? A) 0.025s B) 0.05s C) 0.075s D) 0.1s

Answer: A) 0.025s

Solution: Total distance = 1.2 + 1.8 = 3.0m. Time = Distance ÷ Speed = 3.0 ÷ 120 = 0.025 seconds

Shortcut: 120 m/s means 1m takes 1/120 ≈ 0.0083s, so 3m takes 0.025s

Concept: Biology Human Body - Neural transmission

5 Previous Year Questions

PYQ 1. Which vitamin is synthesized by human skin when exposed to sunlight? [RRB NTPC 2021 CBT-1]

Answer: D) Vitamin D

Solution: Vitamin D (calciferol) is synthesized in the skin from 7-dehydrocholesterol when exposed to UV-B radiation (290-315 nm wavelength).

Exam Tip: Remember “D for Daylight” - only vitamin D is produced by sunlight exposure

PYQ 2. The pH of human blood is approximately: [RRB Group D 2022]

Answer: B) 7.4

Solution: Normal blood pH range: 7.35-7.45 (slightly alkaline). Below 7.35 = acidosis, above 7.45 = alkalosis.

Exam Tip: Remember 7.4 - the decimal 4 looks like a “plus” sign, indicating slightly alkaline

PYQ 3. Which is the largest gland in the human body? [RRB ALP 2018]

Answer: A) Liver

Solution: Liver: 1.5 kg weight, performs 500+ functions including bile production, detoxification, glycogen storage.

Exam Tip: Liver is largest internal organ AND largest gland. Skin is largest organ overall but not a gland.

PYQ 4. Haemoglobin in humans can bind with how many oxygen molecules? [RRB JE 2019]

Answer: C) 4

Solution: Each haemoglobin molecule has 4 heme groups, each binding one O₂ molecule. Formula: Hb + 4O₂ → Hb(O₂)₄

Exam Tip: Remember “4” - same as 4 chambers of heart, 4 blood groups (main types)

PYQ 5. Which part of the brain controls body balance? [RPF SI 2019]

Answer: B) Cerebellum

Solution: Cerebellum (“little brain”) at back of head, coordinates voluntary movements, maintains posture and balance.

Exam Tip: “Cerebellum” has double ’l’ like “balance” - helps remember its function

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Topic Connections

• Direct Link: Physics - Pressure concepts (blood pressure, atmospheric pressure effects on breathing)
• Combined Questions: Chemistry - pH values (blood, stomach acid, urine); Digestive enzymes as catalysts
• Foundation For: Medical emergencies in railway context (first aid, CPR, shock treatment); Occupational health hazards for railway workers