Question 1

Ductless glands that secrete their products (hormones) directly into the blood are called:

Accepted Answer

Endocrine glands. Endocrine glands lack ducts and release hormones into the blood; exocrine glands (e.g. salivary) have ducts.

Question 2

Chemical messengers secreted in small amounts that regulate distant target organs are called:

Accepted Answer

Hormones. Hormones are non-nutrient chemical messengers acting on specific target tissues bearing receptors.

Question 3

The gland often called the "master gland" because it controls many other endocrine glands is the:

Accepted Answer

Pituitary gland. The pituitary secretes tropic hormones controlling other glands — hence "master gland" (itself regulated by the hypothalamus).

Question 4

A deficiency of Growth Hormone (GH) in childhood leads to:

Accepted Answer

Dwarfism. Low GH in children causes pituitary dwarfism; excess causes gigantism.

Question 5

The thyroid hormones (T₃ and T₄) require the element ______ for their synthesis:

Accepted Answer

Iodine. Iodine is essential for thyroxine (T₄) and triiodothyronine (T₃) synthesis.

Question 6

Enlargement of the thyroid gland due to dietary iodine deficiency is called:

Accepted Answer

Goitre. Iodine deficiency → low thyroxine → thyroid enlarges (simple goitre).

Question 7

The hormone secreted by the adrenal medulla during emergencies ("fight or flight") is:

Accepted Answer

Adrenaline (epinephrine). Adrenaline (and noradrenaline) from the adrenal medulla prepares the body for emergencies.

Question 8

The pancreatic hormone that lowers blood glucose by promoting its uptake and storage is:

Accepted Answer

Insulin. Insulin (from β-cells of islets) lowers blood glucose; glucagon (α-cells) raises it.

Question 9

The gland that secretes melatonin and regulates the sleep-wake (diurnal) cycle is the:

Accepted Answer

Pineal gland. The pineal gland secretes melatonin, which maintains the body's circadian rhythm and sleep-wake cycle.

Question 10

The gland that plays a major role in the development of the immune system (T-lymphocytes) is the:

Accepted Answer

Thymus. The thymus secretes thymosins that promote differentiation of T-lymphocytes; it degenerates with age.

Question 11

Protein/peptide hormones (e.g. insulin) act via membrane receptors and ______, whereas steroid hormones act by ______:

Accepted Answer

Second messengers (e.g. cyclic AMP); entering the cell and regulating gene expression. Peptide hormones bind surface receptors and use second messengers; lipid-soluble steroids enter cells and modulate transcription.

Question 12

The organs like the heart, kidney and gastrointestinal tract are considered part of the diffused endocrine system because they:

Accepted Answer

Also produce hormones (e.g. ANF, erythropoietin, gastrin) though not classical endocrine glands. Non-endocrine organs secrete hormones too — heart (ANF), kidney (erythropoietin/renin), gut (gastrin, secretin).

Question 13

The posterior pituitary (neurohypophysis) does NOT synthesise hormones; it stores and releases ______ made by the ______:

Accepted Answer

Oxytocin and vasopressin (ADH); hypothalamus. ADH and oxytocin are made by hypothalamic neurons and merely stored/released by the posterior pituitary.

Question 14

The hypothalamus controls the anterior pituitary by secreting ______ that travel through a ______:

Accepted Answer

Releasing and inhibiting hormones; portal (hypophyseal) blood system. Hypothalamic releasing/inhibiting hormones reach the anterior pituitary through the hypothalamo-hypophyseal portal system.

Question 15

Calcitonin (from the thyroid) and parathormone (from parathyroids) act antagonistically to regulate:

Accepted Answer

Blood calcium levels. Calcitonin lowers and PTH raises blood Ca²⁺ — together they maintain calcium homeostasis.

Question 16

Thyroxine is also a major regulator of the ______ and influences ______:

Accepted Answer

Basal metabolic rate (BMR); growth, RBC formation and tissue development. Thyroxine controls BMR and supports normal growth, erythropoiesis, and metabolism of carbohydrates, fats and proteins.

Question 17

Aldosterone (a mineralocorticoid from the adrenal cortex) mainly regulates:

Accepted Answer

Na⁺ and K⁺ balance and water (blood pressure) by acting on the kidney. Aldosterone promotes Na⁺/water reabsorption and K⁺ excretion in the kidney, controlling electrolyte and fluid balance.

Question 18

The islets of Langerhans have α-cells and β-cells that secrete, respectively:

Accepted Answer

Glucagon and insulin. α-cells secrete glucagon (raises glucose); β-cells secrete insulin (lowers glucose); together they regulate blood sugar.

Question 19

Steroid hormones and thyroxine can enter the target cell and act by:

Accepted Answer

Binding intracellular receptors and regulating gene (DNA) transcription. Lipid-soluble hormones (steroids, thyroxine) cross the membrane, bind nuclear/cytoplasmic receptors and alter gene expression.

Question 20

Protein/peptide hormones like insulin act through the second-messenger mechanism because they:

Accepted Answer

Cannot enter the cell, so they bind surface receptors and generate second messengers (e.g. cAMP). Being water-soluble, peptide hormones bind membrane receptors and trigger intracellular second messengers to produce the response.

Chemical Coordination and Integration — NEET Biology MCQs with Solutions

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Sample questions with solutions