Chemical Coordination and Control MCQs for NEET — Zoology Questions with Answers

The thyroid gland plays a crucial role in regulating the body's basal metabolic rate (BMR). It produces hormones such as thyroxine (T4) and triiodothyronine (T3), which regulate the rate of oxidation in cells and hence ATP production. Therefore, any irregularities in the thyroid gland can indeed alter the BMR. Since statement y explains why statement x is true, option o1 is correct.

Under stress conditions, the body's 'fight or flight' response is activated, which is controlled by the adrenal medulla. This leads to the secretion of adrenaline (epinephrine) and noradrenaline (norepinephrine), which among other things, cause body hairs to stand up (a phenomenon called piloerection). Therefore, statement x is correct. However, statement y is incorrect because the secretion from the adrenal medulla increases under stress, not stops. Hence, option o3 is correct.

Pituitary hormones generally interact with cell surface receptors and require secondary messengers to express their effects. Thus, statement x is correct. However, statement y is incorrect because pituitary hormones do not interact with intracellular receptors.

Hormone receptors are specific, meaning each hormone has its own unique receptor. Therefore, statement y is correct. However, statement x is incorrect because insulin and glucagon each have their own distinct receptors.

Aldosterone is a hormone that stimulates the reabsorption of sodium (Na⁺) ions in the kidneys, which in turn promotes water reabsorption. However, deficiency of aldosterone leads to Addison's disease, not diabetes mellitus. Therefore, statement x is correct and statement y is wrong.

Parathyroid glands, which are located near the thyroid gland, regulate calcium (Ca²⁺) levels in the blood. Surgery on the thyroid gland can sometimes inadvertently damage the parathyroid glands, leading to irregularities in calcium levels. Thus, both statements x and y are correct, and y provides a correct explanation for x.

In cases of thyroid cancer, hyperthyroidism is often observed, which means an increased rate of thyroid hormone synthesis and secretion. Therefore, both statements x and y are correct, and y provides a correct explanation for x.

Over secretion of the adrenal cortex, particularly the zona reticularis, results in the increased production of androgenic steroids. This can lead to the development of male secondary sexual characteristics such as facial hair in females, a condition known as hirsutism. Therefore, both statements x and y are correct, and y provides the correct explanation for x.