Lecture 30 – Renal Physiology V

If ou have an increase in pth you will get an

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If ou have an increase in PTH, you will get an increase in reabsorption of Ca from  tubular filtration in kindest Too high of plasma Ca will inhibit reabsorption of Ca, increase filtration
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Calcium [] decreases Parathyroid detects PTH secreted Increases PTH in plasma Acts in bone for reabsorption Operates in the kidneys, increases phosphate reabsorption and Ca reabsorption Decreases Ca excretion (negative feedback) Activates 125OHD3, which increases circulation levels which acts in kidneys and gastro  tract to increase Ca absorption and increase [Ca] Sunlight induces and increase of vitamin D3 in plasma  D3 converted to 25OHD3 in liver Then increases 125OHD3 in the kidneys This will increase Ca absorption in kidneys and GI Ultimately increases Ca plasma levels Acid-Base Balance Metabolic reactions are highly sensitive to H in the fluids in which they occur Sensitivity due to effects of H on shapes of proteins such as enzymes and change of  shape can result in change of function Consequently H is tightly regulates and part of that regulation occurs in the kidney ECF is slightly acidic Buffering is necessary to maintain a stable and fairly neural pH
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Anything that binds reversibly to H is a buffer The CO2/H2CO3 system discussed respiratory/cardiovascular physiology The major intracellular buffers are proteins and phosphates (eg Hb) Buffering does not eliminate excess H, it only keeps H locked up until balance is  restored Kidneys are ultimately responsive for balancing H gains and losses so that pH remains  within a narrow range Key Concept: kidneys eliminate or replenish H from the body by altering bicarbonate  concentration Elimination of a bicarbonate ion from the body is equivalent to adding a H ion Reabsorbing a bicarbonate ion is equivalent to eliminating an H+ H+/KATPase pumps or Na/H counter transporters are located between tubular lumen  and tubular epithelial cells
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