GENM0703 week2 - The Endocrine System HORMONES substances...

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The Endocrine System HORMONES: substances secreted by endocrine glands and transported in the bloodstream to distant target organs where they elicit specific responses Steroid Hormones Andrew Brown, BABS Sex Hormones Mineralocorticoids Glucocorticoids Cholesterol From diet and synthesis (carried in bloodstream by lipoproteins) Steroid hormones are synthesised from cholesterol 27C Adrenal glands Histological view of Adrenal Cortex Aldosterone : the principal mineralocorticoid, produced from progesterone in the outer zone ( zona glomerulosa) of adrenal cortex increases Na+ uptake raises blood pressure and fluid volume • secreted in response to elevated concentrations of angiotensin II or plasma potassium Mineralocorticoids 21C Glucocorticoids Cortisol : dominant glucocorticoid in humans, synthesized from progesterone in the mid-zone ( zona fasciculata) of the adrenal cortex • Secreted in response to adrenocorticotrophic hormone (ACTH) from the anterior pituitary • involved in stress adaptation (hypoglycaemia, fear, pain, heavy exercise, infection) • elevates blood pressure and Na + uptake • numerous effects on the immune system • production follows a diurnal pattern 21C Sex Hormones Testosterone : an androgen produced from progesterone in the testes • principal male sex hormone • responsible for secondary male sex characteristics, Estradiol : an estrogen, principal female sex hormone, produced in the ovary • responsible for secondary female sex characteristics 19C 18C BABS2202 Steroid Hormones AJB2016 1
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