1. Neural vs Endocrine Coordination
| Feature | Neural coordination | Endocrine coordination |
|---|---|---|
| Signal route | Organised point-to-point neural connections | Hormones carried through body fluids to target tissues |
| Speed / duration | Rapid but short-lived | Provides continuous regulation of cellular functions |
| Signal type | Nerve impulses | Non-nutrient chemical intercellular messengers made in trace amounts |
| Need | Nerve fibres do not innervate every body cell | Coordinates metabolism, growth, development and homeostasis |
2. Anterior vs Posterior Pituitary
| Feature | Adenohypophysis / anterior pituitary | Neurohypophysis / posterior pituitary |
|---|---|---|
| Parts | Pars distalis and pars intermedia | Pars nervosa |
| Hypothalamic relation | Hypothalamic releasing/inhibiting hormones reach through portal circulation | Under direct neural regulation; stores hypothalamus-synthesised hormones |
| Hormones | Pars distalis: GH, PRL, TSH, ACTH, LH, FSH. Pars intermedia: MSH. | Oxytocin and vasopressin / ADH |
| Representative actions | Growth, lactation, endocrine-gland activity, gonadal activity and pigmentation | Uterine contraction/milk ejection; water conservation by kidneys |
3. Thyroid vs Parathyroid Hormones
| Feature | Thyroid: T3 / T4 and TCT | Parathyroid: PTH |
|---|---|---|
| Source | Thyroid follicles make T3/T4; gland also releases thyrocalcitonin | Four parathyroids on back of thyroid |
| Key metabolic role | T3/T4 regulate BMR, RBC formation and metabolism | Calcium homeostasis |
| Ca2+ effect | TCT lowers blood calcium | PTH raises blood calcium: bone resorption, renal reabsorption and intestinal absorption |
| Disorder link | Iodine shortage -> goitre/hypothyroidism; excess -> hyperthyroidism/Graves’ disease | Hypercalcemic hormone |
4. Adrenal Medulla vs Adrenal Cortex
| Feature | Adrenal medulla | Adrenal cortex |
|---|---|---|
| Location / products | Central tissue; epinephrine and norepinephrine (catecholamines) | Outer tissue; glucocorticoids, mineralocorticoids and small androgen amount |
| Major response | Fight-or-flight emergency response | Longer metabolic and electrolyte regulation |
| Key actions | Raises alertness, heartbeat, respiration, glycogenolysis, lipolysis and proteolysis | Cortisol stimulates gluconeogenesis/lipolysis/proteolysis; aldosterone retains Na+ and water, and removes K+/phosphate |
| Clinical point | Rapid stress secretion | Low cortical output causes Addison’s disease |
5. Glucagon vs Insulin
| Feature | Glucagon | Insulin |
|---|---|---|
| Cell source | Alpha cells of islets of Langerhans | Beta cells of islets of Langerhans |
| Target | Mainly hepatocytes | Hepatocytes and adipocytes |
| Metabolic action | Glycogenolysis and gluconeogenesis; reduces cellular glucose use | Increases glucose uptake/use and glycogenesis |
| Blood glucose | Raises it: hyperglycemic hormone | Lowers it: hypoglycemic hormone |
| Disorder | Counterbalances insulin | Deficiency/resistance causes diabetes mellitus; insulin therapy is effective |
6. Androgens vs Estrogens vs Progesterone
| Hormone group | Source | Principal actions |
|---|---|---|
| Androgens / testosterone | Leydig cells of testis | Male accessory-organ function, secondary sex characters, spermatogenesis, libido and anabolic effects. |
| Estrogens | Growing ovarian follicles | Female accessory organs and secondary sex characters, follicular/mammary development and sexual behaviour. |
| Progesterone | Corpus luteum after ovulation | Supports pregnancy; forms mammary alveoli and promotes milk secretion. |
7. Hormones from Other Organs
| Source | Hormone | Function |
|---|---|---|
| Atrial wall | ANF | Released with high BP; vasodilation reduces BP. |
| Kidney | Erythropoietin | Stimulates RBC formation. |
| Stomach | Gastrin | Stimulates HCl and pepsinogen secretion. |
| GI tract | Secretin | Stimulates pancreatic water and bicarbonate secretion. |
| GI tract | CCK | Stimulates pancreatic enzymes and gall-bladder bile secretion. |
| GI tract | GIP | Inhibits gastric secretion and motility. |
8. Membrane-bound vs Intracellular Receptors
| Feature | Membrane-bound receptor | Intracellular receptor |
|---|---|---|
| Location | Cell membrane of target cell | Inside target cell, mostly in nucleus |
| Hormone entry | Hormone normally does not enter cell | Hormone enters to interact with internal receptor |
| Mechanism | Hormone-receptor complex creates second messengers: cAMP, IP3, Ca2+ | Complex regulates gene expression or chromosome function |
| Typical hormones | Peptide, polypeptide and protein hormones | Steroids and iodothyronines |
Receptor specificity Each receptor is specific to a hormone. Complex formation changes target-tissue biochemistry, producing physiological and developmental effects.