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Physiological control of GFR & Renal Blood Flow

Physiological control of GFR & Renal Blood Flow. Sympathetic Nervous System Hormonal and Autacoid control Feedback controls intrinsic to the kidney. Sympathetic Nervous System. Stimulation: ↓ GFR & ↓ Blood Flow Moderate/ Mild Stimulation: Little Effect. Hormonal Control.

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Physiological control of GFR & Renal Blood Flow

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  1. kidney

  2. kidney

  3. Physiological control of GFR & Renal Blood Flow • Sympathetic Nervous System • Hormonal and Autacoid control • Feedback controls intrinsic to the kidney kidney

  4. Sympathetic Nervous System • Stimulation: ↓ GFR & ↓ Blood Flow • Moderate/ Mild Stimulation: Little Effect kidney

  5. Hormonal Control • Catecholamine's: GFR • Angiotensin II : Prevents decrease in GFR B.P Blood volume Salt intake. • Atrial Natriuretic peptide: GFR kidney

  6. Autacoids • Endothelin: ↓ GFR • Blood vessel damage • Toxemia of pregnancy • Renal failure • Endothelial Derived Nitric Factor: ↑ GFR • Normally present in small amounts (vasodilator) • May ↓ in some abnormal conditions → ↓ GFR • Prostaglandins (PGE2 and PGI2): ↑ GFR (drugs that block prostaglandin e.g. NSAID can cause ↓ GFR) • Bradykinin →↑ GFR kidney

  7. Function of blood flow autoregulation Other Tissues and kidney Delivery of OXYGEN at normal level Delivery of NUTRIENTS at normal level Remove WASTE Products of metabolism Despite changes in Arterial pressure. In Kidney Maintains a relatively constant GFR Precise control of excretion of water and solutes kidney

  8. Autoregulation of GFR & Renal Blood Flow These mechanisms Still function in Blood-perfused kidneys That have Been removed from the body, independent of systemic influences

  9. 25% ↑in BP • 100 mmHg to 125 mmHg • If no autoregulation • 25% ↑ in GFR= 225 L/day • Tubular reabsorption= 178.5 L/Day • Urine output= 46.5 L/Day • In reality, much less effect on urinary volume due to kidney

  10. Autoregulation of GFR & Renal Blood Flow 1.Tubulo-Glomerular Feedback 2. Glomerulo-Tubular Balance 3. Myogenic autoregulation. kidney

  11. Tubulo-Glomerular Feedback JuxtaGlomerular Complex= JuxtaGlomerular Cells+ Macula Densa kidney

  12. Tubuloglomerular Feedback Mechanism TWO Componenets • Afferent arteriolar feedback mechanism • Efferent arteriolar feedback mechanism kidney

  13. kidney

  14. Flow rate kidney

  15. Glomerulo -Tubular Balance ↑ Filtration → ↑ Reabsorption • Second line of defense to buffer the effects of spontaneous changes in GFR on urine output. kidney

  16. Myogenic Autoregulation • Stretch → Contraction (resist stretching) • Mechanism: stretch → ↑ Ca++ entry into muscle cells → muscle contraction • Advantages: • Prevent overstretch of vessel wall • Prevent ↑ in GFR • Less important kidney

  17. kidney

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