NEET Chemical Coordination and Integration Previous Year Questions with Solutions

The pituitary gland (hypophysis) is lodged in a bony cavity called sella turcica and is attached to the hypothalamus by a stalk. Anatomically, it is divided into two main lobes: 1. Adenohypophysis: Comprising pars distalis (anterior pituitary) and pars intermedia. 2. Neurohypophysis: Pars nervosa (posterior pituitary).

• • Statement (a) is correct.

Pars distalis region of the anterior pituitary secretes gonadotropins, specifically Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH), which stimulate gonadal activity.

• • Statement (b) is correct.

Pars intermedia secretes only one hormone in humans, called Melanocyte Stimulating Hormone (MSH), which acts on melanocytes to regulate skin pigmentation.

• • Statement (c) is correct.

Prolactin (PRL) is a primary peptide hormone secreted by the lactotroph cells of the pars distalis of the adenohypophysis. It regulates the growth of mammary glands and milk formation. Statement (d) asserts that the pituitary "does not secrete prolactin", which is scientifically false.

• • Therefore, statements (a), (b), and (c) only are correct.

The pancreas is a composite (heterocrine) gland. The endocrine part consists of 1 to 2 million Islets of Langerhans representing only 1 to 2 percent of total pancreatic tissue. The two main cell types are alpha (α) cells and beta (β) cells.

• • α-cells comprise ~20% and β-cells comprise ~70% of islet cells.

Glucagon is a peptide hormone that maintains normal blood glucose levels by acting on hepatocytes to stimulate glycogenolysis (breakdown of glycogen into glucose) and gluconeogenesis, producing hyperglycemia. Insulin is a peptide hormone that enhances cellular glucose uptake and stimulates glycogenesis, lowering blood glucose (hypoglycemia).

• • Statement (1) is correct.
• • Statement (3) is correct.
• • Statement (4) is correct.

Statement (2) claims that α-cells secrete insulin. In reality, insulin is secreted exclusively by β-cells. Therefore, Statement (2) is incorrect.

• • Matches official NTA final answer key Option B / (2).

Hypersecretion of growth hormone (GH) in adults (middle-aged individuals after epiphyseal plate closure) causes disfigurement, especially of the face, hands, and feet. This clinical pathology is termed Acromegaly.

• • A pairs with III.

In females, an LH surge at mid-cycle stimulates the rupture of the mature Graafian follicle and induces ovulation, and maintains the corpus luteum.

• • B pairs with IV.

Vasopressin (Antidiuretic Hormone, ADH), released from neurohypophysis, acts mainly on the distal convoluted tubules and collecting ducts of the nephron to stimulate reabsorption of water and electrolytes.

• • C pairs with I.

Oxytocin acts on the smooth myometrium of the uterus, stimulating vigorous contractions during parturition (child birth) and milk ejection from mammary glands.

• • D pairs with II.

The combined match is A-III, B-IV, C-I, D-II. Looking at the options, this corresponds to Option (2).

• • Matches official NTA final answer key Option B / (2).

Analyzing the specific endocrine functions of tissues outside the traditional pituitary/thyroid glands:

• • A. Heart: The atrial wall of our heart secretes a very important peptide hormone called Atrial Natriuretic Factor (ANF). When blood pressure is increased, ANF is secreted causing vasodilation and thereby decreasing blood pressure. Hence, A matches III.
• • B. Kidney: The juxtaglomerular (JG) cells of kidney produce a peptide hormone called Erythropoietin (EPO) which stimulates erythropoiesis (formation of RBCs in bone marrow). Hence, B matches I.
• • C. Gastro-intestinal tract (GIT): Endocrine cells present in different parts of the gastro-intestinal tract secrete four major peptide hormones: gastrin, secretin, cholecystokinin (CCK), and gastric inhibitory peptide (GIP). Secretin acts on the exocrine pancreas and stimulates secretion of water and bicarbonate ions. Hence, C matches IV.
• • D. Adrenal Cortex: Composed of three distinct layers (zona reticularis, zona fasciculata, zona glomerulosa). The outermost layer (zona glomerulosa) secretes mineralocorticoids, mainly Aldosterone, which regulates sodium and water reabsorption in renal distal tubules. Hence, D matches II.

Consolidating the four organ-hormone associations:

• • A -> III (Heart - Atrial natriuretic factor)
• • B -> I (Kidney - Erythropoietin)
• • C -> IV (Gastro-intestinal tract - Secretin)
• • D -> II (Adrenal Cortex - Aldosterone)

The correct matching option is A-III, B-I, C-IV, D-II, exactly matching Option (4).

The adrenal medulla secretes two catecholamines in response to stress or sympathetic stimulation: adrenaline (epinephrine) and noradrenaline (norepinephrine):

• • Commonly called emergency hormones or hormones of Fight or Flight.
• • They elicit coordinated physiological shifts to prepare the organism for intense physical exertion or survival emergencies.

Evaluating sensory and autonomic responses:

• • Pupillary dynamics (Statement A): Catecholamines stimulate $\alpha_1$-adrenergic receptors on the pupillary dilator muscle, causing pupillary dilation (mydriasis) to maximize visual field and light capture. They do NOT cause pupillary constriction (miosis). Hence, Statement A is INCORRECT.
• • Cutaneous dynamics (Statement C): Adrenaline causes contraction of arrector pili muscles attached to hair follicles, causing piloerection (raising of hairs or "goosebumps"). Hence, Statement C is CORRECT.

Evaluating energy mobilization and cardiac performance:

• • Glucose homeostasis (Statement B): Catecholamines stimulate hepatic and muscular glycogenolysis (breakdown of glycogen into glucose) and lipolysis, sharply elevating blood glucose levels. Thus, adrenaline is a potent hyperglycemic hormone. Hence, Statement B is CORRECT.
• • Cardiovascular output (Statement D): By stimulating $\beta_1$-adrenergic receptors on cardiomyocytes, catecholamines exert positive inotropic effects, significantly increasing the strength of heart contraction and cardiac output. Hence, Statement D is CORRECT.

Statements B, C, and D are correct, while Statement A is false. This corresponds to Option (2).

The pituitary gland (hypophysis cerebri) is divided into two anatomically and embryologically distinct lobes:

• • Adenohypophysis (Anterior Pituitary): Originates from Rathke's pouch (oral ectoderm). Its glandular cells synthesize and secrete true trophic hormones: Growth Hormone (GH), Prolactin (PRL), Thyroid Stimulating Hormone (TSH), Adrenocorticotrophic Hormone (ACTH), Luteinizing Hormone (LH), and Follicle Stimulating Hormone (FSH).
• • Neurohypophysis (Posterior Pituitary / Pars Nervosa): Originates from downward neural outgrowth of the hypothalamus (infundibulum). It contains non-secretory pituicytes and axon terminals of hypothalamic neurosecretory cells.

Mechanism of ADH and Oxytocin production:

• • The cell bodies of neurosecretory neurons located in the supraoptic and paraventricular nuclei of the hypothalamus synthesize Oxytocin and Vasopressin (Anti-diuretic hormone / ADH).
• • These peptide hormones are packaged into neurosecretory granules and transported down unmyelinated axons through the hypothalamo-hypophysial tract to nerve terminals in the neurohypophysis.
• • The posterior pituitary stores and releases them into the systemic circulation upon appropriate physiological stimulation (e.g. osmoreceptor activation for ADH).
• • Thus, the posterior pituitary synthesizes ZERO hormones itself; ADH is synthesized in the hypothalamus.

Anti-diuretic hormone (ADH) is the pituitary-released hormone that is actually synthesized in the hypothalamus, matching Option (2).

Analyzing each endocrine gland and tissue pairing:

• • A. Progesterone: After ovulation, the ruptured Graafian follicle transforms into a temporary yellow endocrine gland called the Corpus luteum. The corpus luteum secretes large amounts of progesterone which is essential for maintenance of the endometrium. Hence, A matches IV.
• • B. Relaxin: NCERT Chapter 3 (Section 3.6) explicitly states: "In addition, in the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary." (Relaxin facilitates parturition by loosening pubic symphysis). Hence, B matches II.
• • C. Melanocyte stimulating hormone (MSH): The adenohypophysis consists of two portions, pars distalis and pars intermedia. In humans, pars intermedia secretes only one hormone: MSH (which acts on melanocytes to regulate skin pigmentation). Hence, C matches I.
• • D. Catecholamines: The Adrenal Medulla secretes adrenaline (epinephrine) and noradrenaline (norepinephrine), commonly designated as catecholamines. Hence, D matches III.

Combining the verified associations:

• • A -> IV (Progesterone - Corpus luteum)
• • B -> II (Relaxin - Ovary)
• • C -> I (Melanocyte stimulating hormone - Pars intermedia)
• • D -> III (Catecholamines - Adrenal Medulla)

The unambiguous combination is A-IV, B-II, C-I, D-III, exactly matching Option (1).

Hormones are divided into four chemical classes: (i) Peptide, polypeptide, protein hormones: insulin, glucagon, pituitary hormones, hypothalamic hormones, etc. (ii) Steroids: e.g., cortisol, testosterone, estradiol and progesterone. (iii) Iodothyronines: thyroid hormones. (iv) Amino-acid derivatives: epinephrine.

Glucagon is a peptide hormone secreted by the alpha-cells of the islets of Langerhans that plays an important role in maintaining normal blood glucose levels (hyperglycemic factor).

Exophthalmic goitre is a form of hyperthyroidism, characterised by enlargement of the thyroid gland, protrusion of the eyeballs, increased basal metabolic rate, and weight loss, also called Graves' disease (A -> III). Hypothyroidism during pregnancy causes defective development and maturation of the growing baby leading to stunted growth (cretinism), mental retardation, low intelligence quotient, abnormal skin, deaf-mutism, etc. (D -> II).

Excess secretion of growth hormone in adults especially in middle age can result in severe disfigurement (especially of the face) called acromegaly (B -> IV). Hypersecretion of cortisol by the adrenal cortex leads to Cushing’s syndrome, characterized by fat accumulation in face ("moon face"), muscle breakdown, and hyperglycemia (C -> I).

A-III, B-IV, C-I, D-II corresponds to Option (2).

Analyzing the anatomical associations of peptide hormones secreted by heart, kidney, and gastrointestinal mucosa:

NCERT states under Hormones of Heart, Kidney and Gastrointestinal Tract: - "CCK acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice, respectively." - "GIP inhibits gastric secretion and motility." - "ANF is secreted by the atrial wall of our heart." - "ADH facilitates water reabsorption from latter parts of the tubule in the kidney."

A-IV is present in Options (1) and (2). B-III uniquely isolates Option (2), ruling out Option (1) which has B-II.

Thyroxine ($T_4$) and triiodothyronine ($T_3$) exert widespread metabolic actions across human tissues:

Analyzing the specific endocrine control of functions C and D: - Function C (Sleep-wake cycle): Regulated by the hormone melatonin, secreted by the pineal gland to maintain 24-hour diurnal circadian rhythms. - Function D (Development of immune system): Regulated by peptide hormones called thymosins, secreted by the thymus gland to promote T-lymphocyte differentiation and humoral antibody production.

NCERT states under Thyroid Gland: "Thyroid hormones play an important role in the regulation of the basal metabolic rate. These hormones also support the process of red blood cell formation... Maintenance of water and electrolyte balance is also influenced by thyroid hormones." Melatonin regulates "24-hour (diurnal) rhythm... sleep-wake cycle". Thymosins play "a major role in the differentiation of T-lymphocytes... development of immune system".

Although primarily excretory organs, the kidneys perform vital endocrine functions. When systemic arterial oxygen tension drops (hypoxia, anaemia, or high altitude), specialized oxygen-sensing juxtaglomerular (JG) cells situated along afferent arterioles secrete the glycoprotein hormone erythropoietin (EPO) into the circulation.

Circulating erythropoietin binds to high-affinity EPO receptors (EpoR) on erythroid progenitor cells (CFU-E and proerythroblasts) in the red bone marrow, rescuing them from apoptosis, accelerating cellular proliferation, and boosting maturation into mature biconcave erythrocytes (RBCs).

- Alpha cells of pancreas: Synthesize and secrete *glucagon*, a hyperglycaemic peptide hormone regulating glycogenolysis. - Rostral adenohypophysis (anterior pituitary): Secretes trophic hormones (GH, PRL, TSH, ACTH, LH, FSH), not erythropoietin. - Bone marrow cells: Act as the effector / target tissue executing erythropoiesis, not the primary endocrine source of EPO.

The posterior pituitary (neurohypophysis) releases vasopressin/ADH. Hyposecretion or impairment of ADH synthesis leads to inability of kidney to conserve water, resulting in copious dilute urine excretion known as Diabetes insipidus. Thus, (a) matches (iii).

Grave's disease is a form of hyperthyroidism characterized by enlargement of the thyroid gland, protrusion of the eyeballs (exophthalmos), increased basal metabolic rate, and weight loss. Thus, (b) matches (i).

Underproduction of hormones by the adrenal cortex (mineralocorticoids and glucocorticoids) alters carbohydrate metabolism, causing acute weakness and fatigue, leading to Addison's disease. Thus, (c) matches (iv).

Hyposecretion of insulin by the beta-cells of the islets of Langerhans in the pancreas impairs glucose uptake, leading to prolonged hyperglycemia, glycosuria, and ketone body formation (Diabetes mellitus). Thus, (d) matches (ii).

The adrenal cortex secretes glucocorticoids (mainly cortisol). Glucocorticoids stimulate gluconeogenesis (synthesis of glucose from non-carbohydrate precursors like amino acids and glycerol), lipolysis, and proteolysis, while inhibiting cellular uptake and utilization of amino acids.

Glucagon is secreted by alpha-cells of the islets of Langerhans; it stimulates glycogenolysis and gluconeogenesis, acting as a HYPERglycemic hormone. Statement (2) incorrectly asserts it causes hypoglycemia.

Insulin acts primarily on hepatocytes (liver cells) and adipocytes (adipose tissue cells), stimulating cellular glucose uptake and glycogenesis. It does not act autocrinely on pancreatic cells.

Insulin promotes rapid movement of glucose from blood to hepatocytes and adipocytes, resulting in a decrease in blood glucose levels (HYPOglycemia). Statement (4) claims it causes hyperglycemia, which is false.