Chapter 18: Body Fluids and Circulation – Case-Based / Source-Based Questions with Answers
CBSE Class 11 Biology Case-Based Questions – Body Fluids and Circulation (NCERT)
Course & Examination Details
- Course: CBSE Class 11 Biology
- Prescribed By: Central Board of Secondary Education
- Based On: NCERT
- Unit: Unit V – Human Physiology
- Chapter: Chapter 18 – Body Fluids and Circulation
- Question Type: Case-Based / Source-Based Questions
- Exam Relevance: CBSE Class 11 Annual Examination, Unit Tests, Competency-Based Assessments
Section A: Blood (Case 1–8)
Case 1
A blood sample shows plasma containing proteins like albumin, globulin, and fibrinogen.
Q1. Identify the fluid component of blood.
Answer:
Plasma is the fluid component of blood that transports proteins, nutrients, hormones, and waste materials.
Q2. State one function of fibrinogen.
Answer:
Fibrinogen helps in blood clotting by forming fibrin threads during coagulation.
Case 2
A patient suffers excessive bleeding even from small wounds.
Q3. Which blood component is likely deficient?
Answer:
Platelets are likely deficient, affecting normal blood clotting.
Q4. Mention one function of platelets.
Answer:
Platelets initiate blood clotting to prevent excessive blood loss.
Case 3
A laboratory report shows low haemoglobin levels.
Q5. Which blood cells are affected?
Answer:
Red blood cells are affected, as they contain haemoglobin.
Q6. State one major function of haemoglobin.
Answer:
Haemoglobin transports oxygen from lungs to body tissues.
Case 4
An infection causes increased production of certain blood cells.
Q7. Which blood cells increase during infection?
Answer:
White blood cells increase during infection.
Q8. Name one type of WBC involved in immunity.
Answer:
Lymphocytes are involved in immune responses.
Case 5
A person suffers from severe allergic reactions.
Q9. Which WBC type is associated with allergy?
Answer:
Basophils are associated with allergic reactions.
Case 6
Excess tissue fluid accumulates in limbs.
Q10. Which body fluid drains excess tissue fluid?
Answer:
Lymph drains excess tissue fluid back into blood circulation.
Case 7
Fat absorption is impaired in a patient.
Q11. Which fluid normally transports absorbed fats?
Answer:
Lymph transports absorbed fats from the intestine.
Case 8
RBC formation is reduced due to kidney malfunction.
Q12. Name the hormone regulating RBC formation.
Answer:
Erythropoietin regulates red blood cell formation.
Section B: Heart & Blood Vessels (Case 9–16)
Case 9
A doctor observes rhythmic contraction of heart even without nerve signals.
Q13. What type of heart is this?
Answer:
It is a myogenic heart.
Case 10
An ECG shows impulse initiation in a specific region of heart.
Q14. Name the natural pacemaker of the heart.
Answer:
The sinoatrial (SA) node is the natural pacemaker.
Case 11
A patient has blockage in arteries supplying heart muscles.
Q15. Which circulation is affected?
Answer:
Coronary circulation is affected.
Case 12
Blood flows only in one direction through heart chambers.
Q16. Which structures ensure this?
Answer:
Heart valves ensure one-way blood flow.
Case 13
Blood pressure is recorded very high in an adult.
Q17. Name this condition.
Answer:
The condition is called hypertension.
Case 14
Veins in legs prevent backflow of blood against gravity.
Q18. Which structure helps in this function?
Answer:
Valves in veins prevent backflow of blood.
Case 15
Exchange of gases occurs efficiently in tissues.
Q19. Which blood vessels facilitate this exchange?
Answer:
Capillaries facilitate exchange of gases and nutrients.
Case 16
Left ventricle appears thicker than right ventricle.
Q20. State the reason.
Answer:
Left ventricle pumps blood to entire body and needs higher pressure.
Section C: Cardiac Cycle & Blood Groups (Case 17–25)
Case 17
A heartbeat produces two distinct sounds.
Q21. What causes the first heart sound?
Answer:
Closure of atrioventricular valves causes the first heart sound.
Case 18
The heart completes one beat in less than a second.
Q22. What is the duration of one cardiac cycle?
Answer:
One cardiac cycle lasts about 0.8 seconds.
Case 19
During a phase, all heart chambers relax.
Q23. Name this phase.
Answer:
This phase is called joint diastole.
Case 20
Blood flows from atria to ventricles during contraction.
Q24. Name this phase.
Answer:
Atrial systole is the contraction phase of atria.
Case 21
A person with AB blood group receives blood safely.
Q25. Why is AB called universal recipient?
Answer:
AB blood group lacks antibodies, allowing transfusion from all groups.
Case 22
Agglutination occurs during mismatched blood transfusion.
Q26. What causes agglutination?
Answer:
Antigen–antibody reaction causes agglutination.
Case 23
An Rh⁻ mother carries an Rh⁺ fetus.
Q27. Name the disorder that may occur.
Answer:
Erythroblastosis fetalis may occur.
Case 24
Blood grouping is done before transfusion.
Q28. Why is this necessary?
Answer:
To prevent fatal transfusion reactions due to agglutination.
Case 25
Heart rate increases during stress.
Q29. Which nervous system stimulates this increase?
Answer:
Sympathetic nervous system increases heart rate.
NCERT & CBSE Compliance Note
✔ Strictly based on NCERT Class 11 Biology
✔ Competency-based, source-linked questions
✔ Fully aligned with CBSE assessment pattern
✔ Ideal for board exams and internal assessments