kidney

kidney

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

Sympathetic Nervous System kidney.lecture 5b 28 May 2019 Sympathetic Nervous System Stimulation: ↓ GFR & ↓ Blood Flow Moderate/ Mild Stimulation: Little Effect kidney dr.rashid mahmood

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

Autacoids Endothelin: ↓ GFR Blood vessel damage Toxemia of pregnancy kidney.lecture 5b 28 May 2019 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 Autacoids are biological factors that are primarily characterized by the effect they have upon smooth muscle. With respect to vascular smooth muscle, there are both vasoconstrictor and vasodilator autacoids. Vasodilator autacoids can be released during periods of exercise. Their main effect is seen in the skin, allowing for heat loss. The word Autacoids comes from the greek "Autos" (self) and "Acos" (drug). These are local hormones, therefore have a paracrine effect. Some notable autacoids are: eicosanoids, angiotensin, neurotensin, NO (nitric oxide), kinins, histamine, serotonin, endothelins, etc. kidney dr.rashid mahmood

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

Autoregulation of GFR & Renal Blood Flow kidney.lecture 5b 28 May 2019 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 dr.rashid mahmood

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

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

Tubulo-Glomerular Feedback kidney.lecture 5b 28 May 2019 Tubulo-Glomerular Feedback JuxtaGlomerular Complex= JuxtaGlomerular Cells+ Macula Densa kidney dr.rashid mahmood

Tubulo glomerular Feedback Mechanism TWO Componenets Afferent arteriolar feedback mechanism Efferent arteriolar feedback mechanism kidney

kidney

Flow rate kidney

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

Myogenic Autoregulation kidney.lecture 5b 28 May 2019 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 dr.rashid mahmood

kidney