Problem 150 - Objective Biology for NEET

Question

Read the assertion and reason carefully to mark the correct option out of the options given below: (a) If both the assertion and the reason are true and the reason is a correct explanation of the assertion. (b) If both the assertion and reason are true but the reason is not a correct explanation of the assertion. (c) If the assertion is true but the reason is false. (d) If both the assertion and reason are false. Assertion: Diabetes insipidus is marked by excessive urination and too much thirst for water. Reason: Anti-diuretic hormone \((\mathrm{ADH})\) is secreted by the posterior lobe of pituitary gland.

Step-by-Step Solution

Answer

The correct answer is option (a). Both the assertion and the reason are true, and the reason is a correct explanation of the assertion.

Step 1: Analyze the Assertion

Diabetes insipidus is a condition that results in frequent urination and increased thirst, which depletes the body fluids. Thus, the assertion is indeed true.

Step 2: Analyze the Reason

The Anti-diuretic hormone (ADH), also known as vasopressin, is indeed secreted by the posterior lobe of the pituitary gland. Its main function is to regulate and balance the amount of water in your body. It does this by controlling the amount of urine your kidneys produce. In turn, a dysfunction in the production of ADH can potentially lead to conditions such as diabetes insipidus. Therefore, this statement is also true.

Step 3: Evaluate if the reason explains the assertion

The reason states that ADH, which regulates the amount of water in the body by controlling urine production, is secreted by the posterior lobe of the pituitary gland. Given the function of the ADH and the symptoms of diabetes insipidus (excessive urination and thirst), the reason is indeed a correct explanation for the assertion.

Key Concepts

Anti-diuretic hormone (ADH)

The anti-diuretic hormone (ADH), also known as vasopressin, plays a crucial role in managing the body's water balance. This hormone is produced in the hypothalamus, a small region of the brain, and is stored and released from the posterior pituitary gland.

When the body needs to conserve water, ADH is released into the bloodstream. It acts primarily on the kidneys, signaling them to reduce the production of urine, effectively making it more concentrated. By doing so, ADH helps to keep the water in the body rather than losing it as urine.

Effects of ADH Dysfunction

If the body does not produce enough ADH or if the kidneys do not respond to it properly, it can lead to a condition known as diabetes insipidus. Patients with this condition experience excessive thirst and urination, as the body fails to conserve water effectively. It's important to understand the impact of ADH levels on the body's fluid regulation to get a clearer picture of how disorders like diabetes insipidus can occur.

Pituitary gland function

Often referred to as the 'master gland,' the pituitary is a pea-sized structure located at the base of the brain. It's responsible for controlling various endocrine functions by releasing hormones that regulate other glands in the body.

The pituitary gland has two major parts: the anterior and posterior lobes. While the anterior lobe produces hormones that regulate growth, thyroid function, and reproductive processes, the posterior lobe has a difference in its role—it stores and releases hormones made by the hypothalamus.

Posterior Lobe Hormones

One of these hormones is ADH, which, as discussed earlier, manages the body's water balance. The proper functioning of this gland is essential for maintaining homeostasis, and any dysfunction can contribute to a variety of health issues, including diabetes insipidus due to an imbalance in ADH secretion.

Homeostasis and hormonal regulation

Homeostasis is the process by which the body maintains a stable internal environment despite changes outside. Hormones are key players in this delicate balancing act, acting as messengers that help regulate body functions.

Hormonal regulation involves a complex series of interactions among different organs and glands. When the balance is upset due to hormonal deficiencies or excesses, problems like diabetes insipidus can surface. The feedback loop involving ADH is a great example of hormonal regulation.

Feedback Mechanisms

Feedback mechanisms involving ADH help to correct the body's water levels. When water concentration in the blood drops, the hypothalamus senses the change, prompting the pituitary gland to release more ADH. Conversely, when water levels are high, ADH release is inhibited to decrease water reabsorption by the kidneys. A breakdown in this feedback loop due to pituitary or hypothalamic dysfunction can lead to the inability to concentrate urine and the symptomatic excessive urination and thirst of diabetes insipidus.