UPSC Prelims 2005 Q89: Science & Technology – Health & Diseases
Assertion (A): The person with diabetes insipidus feels thirsty.
Reason (R): A person with diabetes insipidus suffers from excess secretion of vasopressin.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is not the correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (c) A is true but R is false
Explanation
Diabetes insipidus and vasopressin
| Part | Verdict |
|---|---|
| A. A person with diabetes insipidus feels thirsty | True — excess urination causes thirst |
| R. It is caused by excess vasopressin | False: it is due to deficiency of vasopressin (ADH) |
A is true but R is false: diabetes insipidus is caused by too little ADH (vasopressin), so large volumes of dilute urine are passed and thirst follows.
Answer: (c) A is true but R is false.
Why each option is right or wrong
- (a) Incorrect. R is false, so it cannot explain A.
- (b) Incorrect. R is not true, since the cause is a deficiency of ADH.
- (c) CORRECT. A is true because of water loss, but R is false because the cause is deficiency of vasopressin.
- (d) Incorrect. A is true, as the patient does feel thirsty.
Key point
ADH deficiency: diabetes insipidus. Insulin deficiency: diabetes mellitus.
Remember
Diabetes insipidus is caused by a deficiency of vasopressin.
Common mistakes
- Treating excess ADH as the cause.
- Mixing diabetes insipidus with diabetes mellitus.
- Forgetting the link between ADH and water reabsorption.
Exam tip
ADH (vasopressin): released by the posterior pituitary, controls water balance.
Sources
- NCERT Class XI Biology — Chemical Coordination
- John E. Hall — Guyton and Hall Textbook of Medical Physiology (The Pituitary Hormones and Their Control by the Hypothalamus)