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Posterior Pituitary: ADH

ENDOCRINE PHYSIOLOGY

Stimulates ADH Secretion Increased body fluid osmolality
Decreased blood volume Decreased blood pressure Angiotensin II Pain Stress Nausea and vomiting
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Cells in the paraventricular--"" '

Inhibit ADH Secretion

Decreased body fluid osmolality Increased blood volume Increased blood pressure Atrial natriuretic peptide Ethanol

and supraoptic nuclei receive input from osmoreceptors monitor changes in body fluid osmolality), pcripheral baroreceptors (monitor changes in blood pressure and vołume), and higher neural centers

Antidiurelic hormone descends nerve fibers and is picked up by capillaries o i neurohypophysi;

Antidiurelic hormone (ADH or vasopressin)

Antidiuretic hormone makes distal convoluted tubule permeable to water and thus permits it to be reahsorbed along with actively reabsorbed salt

Antidiuretic hormone makes collecting tubule permeable to water, permitting its reabsorption due to high osmolality of renal medulla

14 to 16 L reabsorbed daily under influence of antidiurelic hormone, resulling in 1 to 2 L of urine in 24 hours

Water and electrolyte exchange between blood and tissues: normal or pathological (edemal

Fluid intake ^ (orał or parenteral)

Water and electrolyte loss via gul (vomiting, diarrhea), via cavities (ascites, effusion), or extemally (sweat, hemorrhage)

90% of filtered water reabsorbed in proximal tubule and Henle's loop due to reabsorption of salts, leaving 15 to 20 L a day \

Approximately

180 Lof fluid filtered from blood

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glomeruli i 24 hours

Ascending limb

of Henles loop

impermeable to

water; actively

re.ihsorhs sali.

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Figurę 8.6 Posterior Pituitary Function (ADH)-

Antidiuretic hormone (ADH), or vasopressin, is involved in the regu- secretion (see also Figurę 6.9). When ADH levels are elevated, a lation of water balance. Changes in body fluid osmolality and blood smali volume of concentrated urine is excreted. When ADH leve!s volume and pressure are the primary physiologic regulators of ADH are Iow, a large volume of dilute urine is excreted.