Lesson 11 of 11 · 13 min
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Endocrine system explained with animation
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Must-know facts
20 facts
- 01Endocrine glands are ductless; hormones are non-nutrient intercellular messengers made in trace amounts.
- 02Hypothalamus: basal part of the diencephalon; GnRH stimulates gonadotrophin release, somatostatin inhibits GH release.
- 03Hypothalamic hormones reach the anterior pituitary through a portal circulation; the posterior pituitary is under direct neural control.
- 04Pars distalis: GH, PRL, TSH, ACTH, LH, FSH. Pars intermedia: MSH only. Pars nervosa: stores and releases oxytocin and vasopressin, made in the hypothalamus.
- 05GH excess in childhood: gigantism; GH deficiency: pituitary dwarfism; GH excess in adults: acromegaly.
- 06ADH (vasopressin) acts on the distal tubules; its impairment causes diabetes insipidus.
- 07LH: ovulation of Graafian follicles and maintenance of corpus luteum in females; androgen secretion in males.
- 08Melatonin from the pineal regulates the 24-hour (diurnal) rhythm.
- 09Thyroid: T₄ and T₃ need iodine; iodine deficiency gives goitre; hypothyroidism in pregnancy gives cretinism.
- 10Exophthalmic goitre (Graves' disease): hyperthyroidism with protruding eyeballs, raised BMR and weight loss.
- 11TCT lowers blood Ca²⁺; PTH raises it (hypercalcemic): bone resorption, renal reabsorption, intestinal absorption.
- 12Four parathyroids on the back of the thyroid; thymosins drive T-lymphocyte differentiation.
- 13Adrenal cortex from outside in: zona glomerulosa, zona fasciculata, zona reticularis.
- 14Cortisol: main glucocorticoid. Aldosterone: main mineralocorticoid (Na⁺ and water in, K⁺ and phosphate out).
- 15Adrenaline and noradrenaline (catecholamines) from the adrenal medulla are the fight-or-flight hormones.
- 16Addison's disease: underproduction of adrenal cortex hormones.
- 17About 1 to 2 million islets, only 1 to 2 per cent of pancreatic tissue; α-cells glucagon (hyperglycemic), β-cells insulin (hypoglycemic).
- 18Leydig cells make androgens; growing follicles make estrogen; corpus luteum makes mainly progesterone.
- 19ANF from the atrial wall lowers blood pressure; erythropoietin from juxtaglomerular cells stimulates RBC formation.
- 20Steroids and iodothyronines use intracellular receptors and act on genes; protein hormones use membrane receptors and second messengers (cAMP, IP₃, Ca⁺⁺).
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Key terms
22 terms
- Endocrine gland
- A ductless gland that releases its secretion, a hormone, without a duct.
- Hormone
- A non-nutrient chemical made in trace amounts that carries a message between cells.
- Neurosecretory cells
- Hypothalamic nerve cells, grouped as nuclei, that make and release hormones.
- Portal circulation
- The vessels that carry hypothalamic hormones to the anterior pituitary.
- Adenohypophysis
- Pars distalis plus pars intermedia; the glandular part of the pituitary.
- Neurohypophysis
- Pars nervosa or posterior pituitary; stores and releases oxytocin and vasopressin.
- Gonadotrophins
- LH and FSH, the pituitary hormones that stimulate the gonads.
- Acromegaly
- Disfigurement, mostly of the face, from excess GH in adults.
- Diabetes insipidus
- Water loss and dehydration when ADH synthesis or release is impaired.
- Goitre
- Enlargement of the thyroid, as in iodine deficiency.
- Cretinism
- Stunted growth and impaired development of a baby from hypothyroidism in pregnancy.
- Hypercalcemic hormone
- A hormone that raises blood Ca²⁺, such as PTH.
- Thymosins
- Thymus peptide hormones that drive T-lymphocyte differentiation and promote antibody production.
- Catecholamines
- Adrenaline and noradrenaline, the fight-or-flight hormones of the adrenal medulla.
- Corticoids
- Hormones of the adrenal cortex: glucocorticoids and mineralocorticoids.
- Addison's disease
- Weakness and fatigue from underproduction of adrenal cortex hormones.
- Islets of Langerhans
- The endocrine part of the pancreas, with glucagon-making α-cells and insulin-making β-cells.
- Glycogenolysis
- Breakdown of glycogen to glucose, stimulated by glucagon and catecholamines.
- Leydig cells
- Interstitial cells between the seminiferous tubules that make androgens.
- Corpus luteum
- The ruptured follicle after ovulation, which secretes mainly progesterone.
- Atrial natriuretic factor
- A peptide from the atrial wall that dilates vessels and lowers blood pressure.
- Second messenger
- A molecule such as cAMP, IP₃ or Ca⁺⁺ made inside the cell when a hormone binds a membrane receptor.