C. The Adrenal Glands Adrenal medulla Adrenal cortex Three specific zones and each produces a specific class of steroid hormone Zona glomerulosa – mineralocorticoids ( Aldosterone ) Zona fasciculata – glucocorticoids ( Cortisole ) Zona reticularis - androgens
Functions of mineralocorticoids Aldosterone exerts the 90% of the mineralocorticoid activity. Cortisol also have mineralocorticoid activity, but only 1/400 th that of aldosterone Aldosterone increases renal tubular (principal cells) reabsorption of sodium & secretion of potassium Excess aldosterone ↑ ECF volume & arterial pressure, but has only a small effect on plasma sodium concentration
Excess aldosterone causes hypokalemia & muscle weakness, & too little aldosterone causes hyperkalemia & cardiac toxicity Excess aldosterone increases tubular (intercalated cells) hydrogen ion secretion, with resultant mild alkalosis Aldosterone stimulates sodium & potassium transport in sweat glands, salivary glands, & intestinal epithelial cells Functions of mineralocorticoids
Effect of cortisol on protein metabolism Reduction of protein storage in all cells except those of liver – ↑ protein catabolism & ↓ protein synthesis Cortisol increases liver & plasma proteins Mobilizes aminoacids from non hepatic cells, thus increase blood amino acid level. ↑ amino acid transport to liver cells & ↓ transport of amino acids into other cells Functions of glucocorticoids
Renin Aldosterone Adrenal cortex Corticosterone Angiotensinogen (Lungs) renal blood flow &/or Na + ++ Juxtaglomerular apparatus of kidneys (considered volume receptors) Angiotensin I Converting enzymes Angiotensin II (powerful vasoconstrictor) Angiotensin III (powerful vasoconstrictor) Renin-Angiotensin System: N.B. Aldosterone is the main regulator of Na + retention.
Effects of Epinephrine Gets you ready to fight or run Heightens your senses, tenses your muscles, openings breathing passages, etc. In response to stress Take less than 30 seconds to kick in and last several minutes
C. Disorders of the Adrenal Gland 1. Hypoaldosteronism loss of water/Na+ Addison’s disease – low aldosterone & cortisol 2. Hyperaldosteronism 3. Cushing’s syndrome hypersecretion of cortisol,androgens,aldosterone
Adrenal glands can malfunction Cushing syndrome – hypersecretion of glucocorticoids by the adrenal cortex characterized by weight gain in the trunk of the body but not arms and legs 15.4 Adrenal glands