Regulation of Glomerular Filtration

Regulation of Glomerular Filtration - There are two...

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Urinary System Regulation of Glomerular Filtration GFR must be finely controlled * If it is too high * Fluid flows through the renal tubules too rapidly for them to reabsorb the usual amount of water and solutes * Urine output rises and creates a threat of dehydration and electrolyte depletion * If it is too low * Fluid flows sluggishly through the tubules and they reabsorb wastes that should be eliminated and azotemia may occur * GFR is adjusted by three homeostatic mechanisms * Renal autoregulation * Sympathetic control * Hormonal control Renal Autoregulation * The ability of the nephrons to adjust their own blood flow and GFR without external (nervous or hormonal) control. * Allows stable fluid and electrolyte balance in spite of alterations in mean arterial pressure. * Therefore, a primary role of the renal autoregulatory mechanism is to regulate intrarenal hemodynamics and intrarenal pressures to levels that maintain an optimal balance with tubular metabolic functions.
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Unformatted text preview: * There are two mechanisms of autoregulation * Myogenic mechanism * Tubuloglomerular feedback Myogenic Mechanism * Keeping mind that GFR = Pgc (filtration pressure) x Kuf (ultrafiltration coefficient) and filtration pressure is a matter of blood pressure (or glomerular capillary pressure) * Blood pressure changes are sensed through stretch receptors and respond accordingly through relaxation or constriction. * afferent arteriolar vasoconstriction would serve to protect the glomerulus from uncontrolled systemic hypertension, * while afferent arteriolar vasodilatation would allow for greater blood flow into the glomerulus in times of hypotension * The autoregulatory system accomplishes this by maintaining the glomerular capillary pressure around 60-70 mm Hg * This ability to maintain renal perfusion pressure and glomerular capillary pressure is impaired when mean arterial pressure drops below 70 mmHg....
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