lecture26and27_Renal3and4 combined

Lecture26and27_Renal - Renal Physiology III and IV Reading Chapter 14 3 Basic Renal Processes Glomerular Filtration Tubular Reabsorption Tubular

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Renal Physiology III and IV Reading : Chapter 14
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3 Basic Renal Processes - Glomerular Filtration - Tubular Reabsorption - Tubular Secretion
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Tubular secretion - the discrete transfer of substance from the peritubular capillaries into the tubular lumen - most important substances secreted by the tubules are H + , K + , and organic anions and cations Hydrogen ions (H + ) - the ability of the kidneys to secrete H + is important for the acid-base balance of the body - - extent of H+ secretion depends on the acidity of the body fluids H + can be secreted by the proximal, distal, and collecting tubules
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K + ions - are actively reabsorbed in the proximal tubule and actively secreted in the distal and collecting tubules. - - K + reabsorption (proximal tubule) is constant and unregulated - almost all filtered K + is reabsorbed K + secretion (distal and collecting tubule) is subject to regulation - almost all K + in the urine is K + that was secreted If K + levels are low - If K + levels are high - K + secretion in the distal portion of the nephron is reduced to a minimum K+ secretion in the distal portion of the nephron is increased Maintaining proper ECF levels of K + is extremely important as high levels will cause cells to depolarize and low levels cause cells to hyperpolarize. This could lead to over or under excitability of neurons and muscle cells. K+ secretion - is coupled to Na + reabsorption by means of the energy- dependent Na + -K + pump (in the basolateral membrane) next slide
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K + secretion - the basolateral pump simultaneously transports Na + into the lateral space and K + into the tubular cell - - once inside the tubular cell, K + diffuses passively down its concentration gradient into the tubular lumen aldosterone (release triggered by high K + levels) increases the rate of K + secretion and Na + reabsorption
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Aldosterone secretion can be triggered by two separate pathways 1) triggered via the renin – angiostensin pathway 2) triggered directly by increased levels of plasma K + (released from the adrenal cortex)
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This note was uploaded on 01/29/2012 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Winter '08 term at UC Davis.

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Lecture26and27_Renal - Renal Physiology III and IV Reading Chapter 14 3 Basic Renal Processes Glomerular Filtration Tubular Reabsorption Tubular

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