Regulation of Na and H2O Balance Flashcards
Major Functions of Early Proximal Tubule
Isosmotic reabsorption of solute and water
Cellular Mechanism of Early Proximal Tubule
Na+-glucose, Na+ amino acid, Na+ phosphate costransporter
hormone action of early proximal tubule
PTH inhibits Na+phosphate cotranpsorter ANG II stimulates Na/H exchange
diuretic function of early proximal tubule
osmotic diuretics Carbonic anhydrase inhibitors
Major Function of Late Proximal tubule
isosmotic reabsorption of solute and water
cellular mechanism of late proximal tubule
NaCl reabsorption driven by Cl- gradient
Hormone action of late proximal tubule
not applicable
diuretic actions of late proximal tubule
carbonic anhydrase inhibitors
Major function of thick ascending limb of the loop of henle
Reabsorption of NaCl without water Dilution of tubular fluid Single effect of countercurrent multiplication Reabsorption of Ca+2 and Mg+2 dirven by lumen-positive potential
Cellular Mechanism of TAL of Loop of Henle
Na+, K+, 2Cl- cotransporter
Hormone action of TAL of loop of henle
ADH stimulates Na+, K+, 2Cl- cotransporter
Diuretic action of TAL loop of henle
Loop diuretics
Major function of Early Distal Tubule
Reabsorption of NaCl without water Dilution of tubular fluid
Cellular mechanism of Early Distal tubule
Na/Cl cotransporter
Hormone action of early distal tubule
PTH sitmulates Ca+2 reabsorption
Diuretic action of early distal tubule
Thiazide diuretics
Major function of late distal tubule and collecting ducts (principle cells)
Reabsorption of NaCl K+ secretion Variable water reabsorption
Cellular mechanisms of late distal tubule and collecting ducts (principle cells)
Na+ channels (ENaC) K channels AQP2 water channels
Hormone action of late distal tubule and collecting ducts (principle cells)
Aldosterone stimulates Na+ reabsorption Aldosterone stimulates K+ secretion ADH stimulates water reabsorption
diuretic action of late distal tubule and collecting ducts (principle cells)
K+ sparing diuretics
Major functions of late distal tubule and collecting ducts (alpha intercalated cells)
Reabsorption of K+ Secretion of H+
cellular mechanism of late distal tubule and collecting ducts (alpha intercalated cells)
H+/K+ ATPase H+ ATPase
Hormone action of late distal tubule and collecting ducts (alpha intercalated cells)
H/K ATPase - none H+ ATPase - aldosterone stimulates H+ secretion
Diuretic action of late distal tubule and collecting ducts (alpha intercalated cells)
H/K ATPase - none H+ ATPase- K+ sparing diuretics
Where is Aldosterone secreted?
zona glomerulosa of the adrenal cortex
Mechanism of action of aldosterone
Aldosterone diffuses into cell and induces synthesis of mRNA for a protein involved with Na+ transport in principal cell
K+ sparing diuretics Mechanism of action
interfere with Na+ reabsorption in the principal cells leads to non working Na/K ATPase so K can’t diffuse into lumen.
Factors that promote Na+ reabsorption
- Activation of renal sympathetic nervous system - Activation of RAAS - Secretion of Aldosterone
Factors that promote Na+ excretion
- Release of ANP, BNP - Release of urodilatin - Intrarenal prostaglandins
Renal Sympathetic activity
increased Na+ reabsorption increased renin secretion ADD IMAGE
Factors that promote Renin secretion
- renal sympathetic stimulation (fall in perfusion pressure sensed at cardiopulmonary baroreceeptors leads to direct stimulation of renin secretion via beta 1 receptor activation in JG apparatus) - tubuloglomerular feedback (dec NaCl deliver to macular densa = inc renin secretion) - intrarenal baroreceptor (wall of afferent arteriole; afferent arteriolar vasoconstriction = dec pressure at granular cells = inc renin secretion
Renal sympathetic stimulation
fall in perfusion pressure sensed at cardiopulmonary baroreceeptors leads to direct stimulation of renin secretion via beta 1 receptor activation in JG apparatus
Tubuloglomerular feedback
dec NaCl deliver to macular densa = inc renin secretion
Intrarenal baroreceptors
located in wall of afferent arteriole; afferent arteriolar vasoconstriction = dec pressure at granular cells = inc renin secretion
What effect would a loop diuretic have on renin secretion?
Loop diuretic causes diuresis leads to decreased ECV and dec perfusion pressure leading to an INCREASE in renin secretion
ANGII stimulates:
- inc systemic arteriolar cosntriction - inc renal arteriolar contriction (efferent > afferent, inc GFR, dec RBF) - inc Na reabsorption at PCT - inc Thirst - inc ADH secretion from posterior pituitary - inc aldosterone secretion from adrenal cortex
Effect of ANGII on Efferent Arteriole
ANGII increases Efferent Arteriolar constriction => inc GFR => dec RBF => increased glomerular hydrostatic pressure => increased filtration
Effect of ANGII on glomerular mesangial cells
Glomerular mesangial cell contraction => dec surface area available for filtration => decrease filtration to offset increase in filtration caused by efferent arteriolar constriction
Response of RAAS to dec ECF vol
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Aldosterone action at late distal convoluted tubule principal cell
reabsorbs Na excretes K, H reabsorbs Cl- hyperaldosteronism = hypokalemia, alkalemia
Feedback control of Aldosterone
things that inhibit aldosterone - decreased plasma K - increased ECV - increased ECF volume - increased BP
Factors controlling aldosterone secretion
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ANP does:
- inc GFR (via afferent dilation/efferent constriction) - inhibits Na reabsorption at medullary collecting duct - decreases renin secretion - decreases aldosterone secretion - systemic vasodilation - decreased AVP secretion, action
ANP response to increased ECF volume
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Urodilatin made by and why:
DCT, CD due to increased atrial pressure and increased ECF volume
Urodilatin mechanism of action
suppresses Na and water reabsorption by medullary collecting duct ***No effect on systemic circulation
Response to increased Na intake
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response to decreased Na intake
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ADH/AVP action
- increased permeability of late distal tubule and collecting duct to water via insertion of aquaporis - increases activity of Na/K/2Cl co transporter - increases urea permeability in the inner medullary collecting ducts
ADH secreted by:
supraoptic nucleus in hypothalmus transported to posterior pituitary gland and released
Control of ADH secertion
osmoreceptors, baroreceptors
Two major stimuli for ADH release
hyperosmolality volume depletion (hypothalamic osmoreceptors more important then hepatic osmoreceptors)
