Chapter 10 — Chemical Coordination and Integration
Key Concepts Quick Recap
| Gland | Hormone | Function |
|---|---|---|
| Hypothalamus | Releasing/inhibiting hormones | Controls anterior pituitary |
| Anterior pituitary | GH, TSH, ACTH, FSH, LH, Prolactin | Stimulates other glands |
| Posterior pituitary | ADH, Oxytocin (stored; made in hypothalamus) | Water reabsorption; uterine contraction |
| Thyroid | T3, T4 (thyroxine), Calcitonin | BMR; growth; blood Ca²⁺ (↓) |
| Parathyroid | PTH (parathormone) | Blood Ca²⁺ (↑); antagonises calcitonin |
| Adrenal cortex | Glucocorticoids (cortisol), Mineralocorticoids (aldosterone) | Stress response; Na⁺ balance |
| Adrenal medulla | Adrenaline (epinephrine), Noradrenaline | Emergency "fight or flight" |
| Pancreas (islets) | Insulin (beta cells), Glucagon (alpha cells) | Blood glucose regulation |
| Gonads | Testosterone (testes), Oestrogen/Progesterone (ovaries) | Reproduction, secondary sexual characters |
| Pineal gland | Melatonin | Circadian rhythm, sleep |
| Thymus | Thymosin | T-cell maturation, immunity |
I. Choose the Best Answer (MCQs)
1. The "master gland" of the endocrine system is: (a) Thyroid (b) Adrenal gland (c) Pituitary gland (d) Hypothalamus
2. Insulin is produced by which cells of the pancreas? (a) Alpha cells (b) Delta cells (c) Beta cells (d) Acinar cells
Acinar cells are exocrine (produce digestive enzymes) — not endocrine.
- Beta cells (B cells): ~70% → secrete Insulin (lowers blood glucose).
- Alpha cells (A cells): ~25% → secrete Glucagon (raises blood glucose).
- Delta cells: ~5% → secrete Somatostatin (inhibits glucagon and insulin).
3. Deficiency of iodine in diet leads to: (a) Diabetes insipidus (b) Simple goitre (c) Cretinism (d) Both b and c
Prevention: iodised salt.
- Simple (endemic) goitre: Iodine deficiency → low T3/T4 → TSH increases → thyroid gland enlarges (compensates).
- Cretinism: Iodine deficiency in infants → low thyroxine → mental retardation, stunted growth, delayed sexual development.
4. The hormone responsible for the "fight or flight" response is: (a) Cortisol (b) Aldosterone (c) Adrenaline (d) Insulin
5. Which hormone promotes water reabsorption in the kidney collecting duct? (a) Aldosterone (b) ADH (c) GH (d) PTH
6. The hormone that raises blood calcium levels is: (a) Calcitonin (b) PTH (c) ADH (d) Insulin
Calcitonin (from thyroid) does the opposite: lowers blood Ca²⁺.
- Stimulating osteoclasts → bone resorption → Ca²⁺ released.
- Increasing Ca²⁺ reabsorption in kidney tubules.
- Stimulating Vitamin D activation → Ca²⁺ absorption from gut.
7. Thymosin, important for immunity, is secreted by: (a) Thyroid (b) Parathyroid (c) Thymus (d) Adrenal cortex
II. Short Answer Questions
Common Mistakes
- Confusing thyroid (calcitonin lowers Ca²⁺) vs parathyroid (PTH raises Ca²⁺).
- Saying posterior pituitary MAKES ADH and Oxytocin — it only STORES and RELEASES them; they are synthesised in hypothalamus.
- Confusing alpha cells (glucagon — raises glucose) and beta cells (insulin — lowers glucose).
- Forgetting thymosin is from thymus (not thyroid).
Exam Checklist
- Master gland: pituitary (controlled by hypothalamus).
- Beta cells → insulin (↓ glucose); alpha cells → glucagon (↑ glucose).
- Iodine deficiency: goitre (adults) + cretinism (infants).
- Adrenaline = adrenal medulla → fight or flight.
- Cortisol = adrenal cortex → stress response; aldosterone → Na⁺ and water reabsorption.
- PTH (parathyroid) → ↑ blood Ca²⁺; calcitonin (thyroid) → ↓ blood Ca²⁺.
- ADH: posterior pituitary → water reabsorption in collecting duct.
- Thymosin: thymus → T-lymphocyte maturation.