NCERT Class 11 Science — Chapter 9: Chemical Coordination and Integration

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Assertion (A): Vasopressin is synthesized by the posterior pituitary gland. Reason (R): Vasopressin stimulates the reabsorption of water and electrolytes by the distal tubules.

Official previous-year question

Verified 1 Aug 2026.

Options

ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is NOT the correct explanation of A
CA is true but R is false
DA is false but R is true

Did you get this right?

Solution

The correct option is

A is false but R is true

Explanation

Vasopressin, also known as Antidiuretic Hormone (ADH), is a neurohypophysial hormone crucial for osmoregulation and the maintenance of body fluid volume.

Statement-wise Analysis:

Assertion (A): Incorrect. Vasopressin is not synthesized by the posterior pituitary gland. It is synthesized by the hypothalamus (specifically in the supraoptic and paraventricular nuclei). The posterior pituitary (neurohypophysis) acts merely as a storage and release center. The hormone is transported axonally from the hypothalamus to the posterior pituitary, where it is stored until released into the bloodstream.
Reason (R): Correct. Vasopressin acts mainly on the kidney's distal convoluted tubules (DCT) and collecting ducts. It increases the permeability of these tubules to water by inserting aquaporin channels, thereby stimulating the reabsorption of water and electrolytes. This process concentrates the urine and reduces water loss.

Key Takeaway: The posterior pituitary gland does not synthesize hormones; it stores and releases oxytocin and vasopressin, which are synthesized in the hypothalamus.

Your note

More from Chapter 9: Chemical Coordination and Integration

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Regarding exophthalmic goitre (Graves' disease), which of the following is/are correct? 1. It is a form of hyperthyroidism. 2. It involves sinking of the eyeballs. 3. It is characterised by an increased basal metabolic rate. Select the correct answer using the code below:

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Assertion (A): Thyrocalcitonin (TCT) helps regulate blood calcium levels. Reason (R): Parathyroid hormone (PTH) acts on bones to stimulate bone resorption.

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With reference to parathyroid hormone (PTH), consider the following statements: 1. Its secretion is regulated by circulating sodium levels. 2. It increases bone resorption and renal reabsorption of calcium. 3. It increases calcium absorption from the digested food. Which of the statements given above are correct?

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The correct option is

A is false but R is true

Explanation

Vasopressin, also known as Antidiuretic Hormone (ADH), is a neurohypophysial hormone crucial for osmoregulation and the maintenance of body fluid volume.

Statement-wise Analysis:

Assertion (A): Incorrect. Vasopressin is not synthesized by the posterior pituitary gland. It is synthesized by the hypothalamus (specifically in the supraoptic and paraventricular nuclei). The posterior pituitary (neurohypophysis) acts merely as a storage and release center. The hormone is transported axonally from the hypothalamus to the posterior pituitary, where it is stored until released into the bloodstream.
Reason (R): Correct. Vasopressin acts mainly on the kidney's distal convoluted tubules (DCT) and collecting ducts. It increases the permeability of these tubules to water by inserting aquaporin channels, thereby stimulating the reabsorption of water and electrolytes. This process concentrates the urine and reduces water loss.

Key Takeaway: The posterior pituitary gland does not synthesize hormones; it stores and releases oxytocin and vasopressin, which are synthesized in the hypothalamus.