Control of tubular reabsorption*** Flashcards
What are the mechanisms controlling tubular reabsorption?
Glomerulotubular balance
Pressure natriuresis, pressure diuresis
What is glomerulotubular balance?
Refers to how if the GFR changes, the rate of reabsorption changes in the same direction by a similar degree
How does glomerulotubular balance affect the percentages of ions/small molecules reabsorbed?
It doesn’t, they stay the same
What is the purpose of glomerulotubular balance?
To prevent changes in GFR
from giving large changes in the amount of ions, water that is reabsorbed or excreted
What is pressure natriuresis?
Refers to how increases in blood pressure leads to increases in sodium ion excretion to decrease blood pressure back to normal
What is pressure diuresis?
Refers to how increases in blood pressure leads to increases in water excretion to decrease blood pressure back to normal
How do pressure natriuresis and pressure diuresis relate to each other?
Occur simultaneously
How does pressure natriuresis work?
Afferent arteriole senses stretch
suppresses renin release from juxtaglomerular cells
reduced angiotensin 2
also reduced aldosterone
What are the effects of reduced angiotensin 2?
Dilation of efferent arteriole
Reduced activity of NHE on apical domain of eptihelial cells in PCT
What is the effect of dilation of the efferent arteriole?
Increased blood flow through efferent arteriole into peritubular capillaries
higher hydrostatic pressure in peritubular capillaries, lower oncotic pressure
less reabsorption of sodium and water
What is the effect of reduced activity of NHE on the apical domain of epithelial cells in the PCT?
Reduced sodium ion and water reabsorption
What is the effect of reduced aldosterone?
Reduced expression of ENaC on apical domain of epithelial cells in later DCT and CD
What is the effect of fewer ENaC on apical domain of epithelial cells in DCT and CD?
Reduced sodium ion and water reabsorption
What part of the nephron does pressure natriuresis and diuresis affect?
Proximal convoluted tubule
Later distal convoluted tubule
Collecting duct
