Endocrine System — Set 5

Correct Answer: A. Sweat gland

• **Sweat gland** = exocrine glands release their secretions through ducts onto body surfaces or into body cavities; sweat glands secrete sweat via ducts directly onto the skin surface for temperature regulation and waste excretion. • **Key fact** — The defining difference: endocrine glands (ductless) secrete hormones into the bloodstream; exocrine glands (ducted) deliver secretions to a specific surface — other exocrine examples include salivary glands, liver (bile), and pancreatic acini (digestive enzymes). • The pancreas is both — its acinar cells are exocrine (digestive enzymes via pancreatic duct) while its islets of Langerhans are endocrine (insulin, glucagon into blood). • 💡 Option B (Thyroid) is ductless and secretes T3/T4 into blood; Option C (Pituitary) releases tropic hormones into blood; Option D (Adrenal) secretes cortisol and adrenaline into blood — all three are endocrine glands.

Correct Answer: C. Tyrosine

• **Tyrosine** = Thyroxine (T4) and Triiodothyronine (T3) are both synthesised from the amino acid tyrosine by coupling it with iodine atoms in the thyroid gland — T4 has four iodine atoms and T3 has three. • **Key fact** — This is why dietary iodine is essential for thyroid function; iodine deficiency prevents T3/T4 synthesis, causing the thyroid to enlarge (goitre) in a futile effort to compensate. • Tyrosine is also the precursor for dopamine, noradrenaline, and adrenaline — making it one of the most metabolically versatile amino acids. • 💡 Option A (Glycine) is the simplest amino acid with no ring structure; Option B (Alanine) is a non-polar aliphatic amino acid; Option D (Tryptophan) is the precursor to serotonin and melatonin — none are iodinated to form thyroid hormones.

Correct Answer: B. Gastrin

• **Gastrin** = secreted by G-cells in the antrum of the stomach and duodenum, gastrin stimulates parietal cells to secrete hydrochloric acid and chief cells to release pepsinogen, together constituting gastric juice for protein digestion. • **Key fact** — Gastrin secretion is triggered by protein in the stomach, stomach distension, and vagal stimulation (thinking about food); it is inhibited when stomach pH drops below 3, acting as a negative feedback loop. • Zollinger-Ellison syndrome is caused by a gastrin-secreting tumour (gastrinoma) that produces massive acid, leading to severe peptic ulcers. • 💡 Option A (Insulin) reduces blood glucose — it has no role in gastric juice; Option C (Secretin) neutralises acid in the duodenum by triggering bicarbonate release from the pancreas; Option D (CCK) acts on the gallbladder and pancreatic enzymes, not gastric acid.

Correct Answer: C. Stimulating growth

• **Stimulating growth** = Somatotropin is simply another name for Growth Hormone (GH), secreted by somatotroph cells of the anterior pituitary; it promotes longitudinal bone growth by stimulating production of IGF-1 (insulin-like growth factor-1) in the liver, which directly stimulates cartilage and bone growth. • **Key fact** — GH is released in pulses, predominantly during deep sleep (Stage 3/4 NREM), which explains why adequate sleep is essential for normal growth in children and tissue repair in adults. • The name 'somatotropin' comes from Greek: soma = body, tropin = to nourish/stimulate. • 💡 Option A (Producing milk) is the role of Prolactin; Option B (Regulating calcium) is done by PTH and Calcitonin; Option D (Controlling heart rate) is done by the autonomic nervous system via adrenaline and noradrenaline.

Correct Answer: A. Gibberellin

• **Gibberellin** = plant hormones produced in young leaves, roots, and seeds; gibberellins promote cell elongation, seed germination, fruit development, and — critically — the differentiation of microsporangia (pollen-producing anther structures) in flowers. • **Key fact** — Gibberellins were first discovered in Japan in the 1920s when studying 'bakanae' (foolish seedling) disease in rice, caused by the fungus Gibberella fujikuroi, which produces gibberellin-like compounds causing abnormal elongation. • GA3 (Gibberellic acid) is commercially used to produce seedless grapes and increase fruit size. • 💡 Option B (Cytokinin) promotes cell division and delays leaf senescence; Option C (Auxin) controls phototropism and apical dominance; Option D (Ethylene) is a gaseous hormone that triggers fruit ripening and leaf abscission — none specifically regulate pollen structure development.

Correct Answer: B. Acromegaly

• **Acromegaly** = when Growth Hormone is excessively secreted after the epiphyseal (growth) plates have fused in adulthood, bones cannot lengthen but instead thicken — causing enlarged jaw, protruding brow, spade-like hands, and enlarged feet characteristic of acromegaly. • **Key fact** — Over 95% of acromegaly cases are caused by a benign GH-secreting pituitary adenoma; treatment includes surgery (transsphenoidal), somatostatin analogues (octreotide), and GH receptor antagonists. • The word 'acromegaly' comes from Greek: akron = extremity, megas = large — referring to the enlarged extremities. • 💡 Option A (Dwarfism) results from GH deficiency; Option C (Gigantism) is GH excess in childhood before plates fuse — giving excessive height, unlike acromegaly; Option D (Goitre) is thyroid enlargement due to iodine deficiency or thyroid disease, unrelated to GH.

Correct Answer: A. Increasing alertness and blood pressure

• **Increasing alertness and blood pressure** = Noradrenaline (norepinephrine) acts as both a hormone (from adrenal medulla) and a neurotransmitter (in sympathetic nerves); it causes vasoconstriction, raising blood pressure, and increases alertness, focus, and readiness during stress or threat. • **Key fact** — Noradrenaline has stronger alpha-adrenergic (vasoconstrictor) effects than adrenaline; adrenaline has stronger beta-adrenergic (heart rate and bronchodilation) effects — together they cover the full fight-or-flight spectrum. • Low noradrenaline in the brain is linked to depression and ADHD; drugs like norepinephrine reuptake inhibitors (SNRIs) target this system. • 💡 Option B (Digesting proteins) is a function of pepsin and trypsin, not hormones; Option C (Lowering blood pressure) is the opposite effect — noradrenaline raises it; Option D (Inducing sleep) is the role of melatonin from the pineal gland.

Correct Answer: C. Oxytocin

• **Oxytocin** = produced in the hypothalamus (specifically paraventricular and supraoptic nuclei) and stored in and released from the posterior pituitary — not the anterior pituitary; it stimulates uterine contractions during childbirth and milk let-down during breastfeeding. • **Key fact** — The anterior pituitary (adenohypophysis) is a true glandular tissue; the posterior pituitary (neurohypophysis) is neural tissue that stores hypothalamic hormones — Oxytocin and ADH (vasopressin). • Synthetic oxytocin (Pitocin) is widely used in obstetrics to induce or augment labour. • 💡 Option A (Prolactin) is secreted by the anterior pituitary to stimulate milk production; Option B (Growth Hormone) is also from the anterior pituitary; Option D (TSH) is a tropic hormone from the anterior pituitary that stimulates the thyroid gland.

Correct Answer: D. Stimulating sperm production

• **Stimulating sperm production** = in males, FSH from the anterior pituitary acts on Sertoli cells in the seminiferous tubules of the testes, promoting spermatogenesis — the production and maturation of sperm cells. • **Key fact** — FSH works together with LH in males: FSH drives sperm production while LH stimulates Leydig cells to produce testosterone; both are required for normal male fertility. • Men with low FSH have impaired sperm production (oligospermia or azoospermia) despite normal testosterone — FSH is tested in male infertility workups. • 💡 Option A (Producing testosterone) is the role of LH acting on Leydig cells; Option B (Regulating metabolism) is the function of thyroid hormones; Option C (Deepening the voice) is caused by testosterone acting on the larynx during puberty, not FSH.

Correct Answer: D. Diabetes Mellitus

• **Diabetes Mellitus** = insulin is produced by beta cells of the pancreas and allows cells to absorb glucose from the blood; its deficiency (Type 1) or ineffective action (Type 2) results in chronically high blood glucose (hyperglycaemia) — the hallmark of Diabetes Mellitus. • **Key fact** — Without insulin, glucose cannot enter most body cells, so the body catabolises fat for energy, producing ketones — in Type 1 diabetes this can lead to life-threatening diabetic ketoacidosis (DKA). • Classic symptoms are the '3 Polys': Polyuria (frequent urination), Polydipsia (excessive thirst), and Polyphagia (excessive hunger). • 💡 Option A (Addison's Disease) is cortisol deficiency; Option B (Graves' Disease) is thyroid hormone excess causing hyperthyroidism; Option C (Diabetes Insipidus) is caused by ADH deficiency — it causes excessive water loss but has nothing to do with blood sugar or insulin.