afferent efferent arteriole arteriole glomerular capillaries Bowmans capsule 1. Filtration 2. Reabsorption peritubular 3. Secretion capillaries 4. Excretion 63 renal vein 4 urinary excretion
1600 1200 80 Renal blood flow Glomerular filtration rate 8 日 2 50 100 150 200 Arterial pressure(mm Hg) 4080120160200240280 MEAN ARTERIAL PRESSURE pressure-diuresis curve
pressure-diuresis curve
Ill. The pressure-natriuresis and ressure-diuresis Even with these special control mechanisms, changes in arterial pressure still have significant effects on renal excretion of water and sodium (1) The slight increase in GFR that does occur contributes in part to the effect of increased arterial pressure on urine output(P→GFR↑→Uout1) (2 )This effect result in part from a slight increase in ritubular capillary hydrostatic pressure especially in the vasa recta of the renal medulla, and a subsequent increase in the renal interstitial fluid hydrostatic pressure.(P↑→ p cap hyd p↑→ reabsorb」→ Uout t) (3)Decreased angiotensin I formation contributes to the decreased tubular sodium reabsorption that occurs when arterial pressure is increased (P↑→Ag‖↓→ eabsob↓→out)
III. The pressure-natriuresis and pressure-diuresis Even with these special control mechanisms, changes in arterial pressure still have significant effects on renal excretion of water and sodium. (1) The slight increase in GFR that does occur contributes in part to the effect of increased arterial pressure on urine output. ( P↑ → GFR ↑ →Uout ↑) (3)Decreased angiotensin II formation contributes to the decreased tubular sodium reabsorption that occurs when arterial pressure is increased. (P↑ → AgII ↓ →reabsob↓ →Uout ↑) (2) This effect result in part from a slight increase in peritubular capillary hydrostatic pressure, especially in the vasa recta of the renal medulla, and a subsequent increase in the renal interstitial fluid hydrostatic pressure. (P↑ → p cap hyd p ↑ →reabsob↓ →Uout ↑)
When the arterial pressure changes slowly over many hours or days or week-after-week, or month- after month, the nervous mechanisms gradually lose all or almost all of their ability to oppose the changes
When the arterial pressure changes slowly over many hours or days, or week-after-week, or monthafter month, the nervous mechanisms gradually lose all or almost all of their ability to oppose the changes
Cardiac outpu 2000 1000 Infusion period Arterial pressure 505050 4 Urinary output 0102030405060 Time minutes Increase in cardiac output, (urniary)urinary output, and arterial pressure caused by increased blood volume in dogs whose nervous oressure control mechanisms had been blocked. This figure shows the return of arterial pressure to normal after about an hour of fluid loss into the urine. Bourtrsy Dr. Wolliam Dobbs
Increase in cardiac output, (urniary) urinary output, and arterial pressure caused by increased blood volume in dogs whose nervous pressure control mechanisms had been blocked. This figure shows the return of arterial pressure to normal after about an hour of fluid loss into the urine. (Bourtrsy Dr. Wolliam Dobbs.) Infusion period Time minutes Cardiac output Arterial pressure Urinary output