Chapter 18: Body Fluids & Circulation
NCERT Solutions for CBSE Class 10 Biology — 19 solved questions with detailed explanations.
Solved Questions
Q1. The pacemaker of the heart is the:
- AV node
- SA node
- Bundle of His
- Purkinje fibers
Difficulty: Easy · Topic: Heart
Solution
SA node (sinoatrial node) is the natural pacemaker. It generates impulses at 70-75 beats/min.
Q2. Platelets are involved in:
- immunity
- pH balance
- oxygen transport
- blood clotting
Difficulty: Easy · Topic: Body Fluids & Circulation
Q3. The cardiac cycle duration is approximately:
- 0.5 seconds
- 0.8 seconds
- 2 seconds
- 1.5 seconds
Difficulty: Easy · Topic: Body Fluids & Circulation
Q4. Lub (first heart sound) is due to:
- opening of semilunar valves
- closure of AV valves
- opening of AV valves
- closure of semilunar valves
Difficulty: Easy · Topic: Body Fluids & Circulation
Solution
closure of AV valves.
Q5. RBCs are produced in:
- liver
- spleen
- lymph nodes
- red bone marrow
Difficulty: Easy · Topic: Body Fluids & Circulation
Q6. RBC lifespan is approximately:
- 30 days
- 7 days
- 365 days
- 120 days
Difficulty: Easy · Topic: Body Fluids & Circulation
Q7. WBC lifespan varies from:
- always 30 days
- always 120 days
- always 7 days
- few hours to years
Difficulty: Easy · Topic: Body Fluids & Circulation
Solution
few hours to years.
Q8. Platelet lifespan is approximately:
- 120 days
- 8-10 days
- 30 days
- 1 day
Difficulty: Easy · Topic: Body Fluids & Circulation
Q9. Fibrinogen is converted to fibrin by:
- plasmin
- thrombin
- pepsin
- trypsin
Difficulty: Easy · Topic: Body Fluids & Circulation
Q10. Heparin is a natural:
- enzyme
- anticoagulant
- hormone
- coagulant
Difficulty: Easy · Topic: Body Fluids & Circulation
Q11. Lymph differs from blood by lacking:
- electrolytes
- RBCs and most proteins
- WBCs
- water
Difficulty: Easy · Topic: Body Fluids & Circulation
Solution
RBCs and most proteins.
Q12. Double circulation means:
- blood flows once
- heart pumps once
- blood passes through heart twice per circuit
- no circulation
Difficulty: Easy · Topic: Body Fluids & Circulation
Solution
blood passes through heart twice per circuit.
Q13. Portal vein carries blood from:
- kidneys to heart
- brain to heart
- heart to lungs
- intestine to liver
Difficulty: Easy · Topic: Body Fluids & Circulation
Solution
intestine to liver.
Q14. Cardiac output = :
- stroke volume only
- blood pressure
- heart rate only
- heart rate × stroke volume ≈ 5L/min
Difficulty: Easy · Topic: Body Fluids & Circulation
Solution
heart rate × stroke volume ≈ 5L/min.
Q15. Blood group O is called the universal donor because:
- It has both A and B antigens
- It has no A or B antigens on RBCs
- It has both antibodies
- It has Rh factor
Difficulty: Easy-Medium · Topic: Blood Groups
Solution
Type O blood has no A or B antigens on RBCs, so it won't trigger immune response in any recipient.
Q16. WBCs are involved in:
- immunity/defense
- pH regulation
- oxygen transport
- clotting
Difficulty: Easy-Medium · Topic: Body Fluids & Circulation
Solution
immunity/defense.
Q17. Dub (second heart sound) is due to:
- ventricular contraction
- closure of semilunar valves
- opening of AV valves
- closure of AV valves
Difficulty: Easy-Medium · Topic: Body Fluids & Circulation
Solution
closure of semilunar valves.
Q18. ECG P wave represents:
- ventricular repolarization
- ventricular depolarization
- atrial repolarization
- atrial depolarization
Difficulty: Easy-Medium · Topic: Body Fluids & Circulation
Solution
atrial depolarization.
Q19. ECG QRS complex represents:
- ventricular depolarization
- atrial depolarization
- atrial repolarization
- ventricular repolarization
Difficulty: Easy-Medium · Topic: Body Fluids & Circulation
Solution
ventricular depolarization.
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