Regulation of Sodium and Water Balance Flashcards
What happens to Na excretion and Na retention when ECF volume is low?
Na excretion will be low and Na retention will be high
What happens to Na excretion and Na retention when ECF volume is high?
Na excretion will be high and Na retention will be low
Which of the following has a negative effect on Na excretion?
A. Dopamine
B. Natriuretic peptides
C. Sympathetic stimulation
D. ECF volume
C. Sympathetic stim
What are the 3 main things that promote renin secretion?
Sympathetic stim directly via B1 receptor activation in JG apparatus
Decreased NaCl delivery to macula densa
Afferent arteriolar vasoconstriction leading to decreased pressure at granular cells
What effects do increased afferent arterolar pressure or ADH have on renin secretion?
Inhibits it
Aldosterone increases the synthesis of Na/K ATPase in the basolateral membrane of the distal tubule - what is the overall effect?
Increase in Na reabsorption and increase in K excretion
What is the aldosterone receptor?
MR
2 main actions of aldosterone in terms of membrane channels
Increases synthesis and activity of Na/K ATPase in basolateral membrane of DT
Increased synthesis and activity of ENaC channels in apical membrane
3 main actions of aldosterone in terms of ion reabsorption/secretion
Increases Na reabsorption
Increases K+ secretion
Increases H+ secretion
What 2 physiological changes is ADH secreted in response to and which one is it more sensitive to?
Hyperosmolarity (most sensitive)
Volume depletion
ADH is released in conditions of hyperosmolarity and volume depletion, what receptors detect these changes
Osmoreceptors in the hypothalamus and liver
Baroreceptors in aorta and carotid sinus
3 main actions of ADH in kidney tubules
Increases water permeability of principal cells of collecting duct via insertion of aquaporins into luminal membrane
Increases urea permeability in inner medullary CD’s
Increases activity of Na/K/2Cl cotransporter in TAL
ADH receptor
V2 receptor
Which aquaporin is inserted into the luminal membrane in response to ADH? What happens when ADH decreases again?
Aquaporin 2
When ADH decreases, aquaporin 2 is endocytosed
What are the 2 main osmoreceptor areas that respond to ADH, and what is unique about them
OVLT and SFO; they extend outside the BBB
Osmoreceptors are located in the OVLT and SFO, 2 areas that breech the BBB. A second neuron carries the signal to the hypothalamus. The osmosensitive ________ neurons project to large diameter neurons in the supraoptic and paraventricular nuclei of the _________. ADH is carried along the axon to posterior pituitary where it is released to circulation
Magnocellular; hypothalamus
Which of the following inhibits ADH secretion?
A. Nausea
B. Angiotensin II
C. Nicotine
D. Ethanol
D. Ethanol
[ANP also inhibits ADH]
Action/source of ANP/BNP
ANP from heart atria
BNP from heart ventricles
Promotes NaCl and water secretion; elevates GFR; systemic vasodilator
What is urodilatin
Locally produced in the kidney; promotes NaCl secretion
T/F: Natriuretic peptides generally oppose RAAS, SNS, and ADH
True
Effect of natriuretic peptides on GFR
Increases GFR by afferent vasodilation and efferent vasoconstriction
Increased activity of the RAAS is the first of four parallel pathways that correct a low ECV. What are the other 3 pathways?
Sympathetic stimulation
Posterior pituitary activation and ADH release
ANP activity inhibited
Integrated response to volume expansion:
_______ in GFR
________ in reabsorption of Na in the proximal tubule and LOH
_______ of water
Increase
Decrease
Excretion
Integrated response to decreased ECV involves renin release. What stimulates renin release?
_______ BP
________ NaCl delivery to macula densa
_________ renal perfusion pressure
Decrease
Decrease
Decrease
Integrated response to decreased ECV: actions of angiotensin II:
______ aldosterone
________ efferent arteriole
_________ Na-H exchange
________ thirst and ADH release
Increase
Vasoconstrict
Enhance
Stimulate
Integrated response to decreased ECV: effect of sympathetics:
______ renal vascular resistance
_______ Na reabsorption
________ renin release via JG cells
Increase
Increase
Enhance
In the integrated response to decreased ECV, ANP activity is _______
Inhibited
Ingtegrated response to volume contraction:
______ in GFR
_______ in Na reabsorption by PT and LOH
_______ water reabsorption
Decrease
Increase
Enhanced
Disorders of ECF volume are usually the result of disturbances in _____ balance, and disorders of sodium concentration are usually the result of disturbances in ______ balance
Sodium
Water
T/F: you can depend on serum sodium concentration to tell you about the state of fluids in the vascular compartment
False
You also have to consider whether RAAS has had time to elicit effects, as well as the person’s access to water/hydration status
Effect of primary polydipsia on serum ADH, serum osmolarity, urine osmolarity, urine flow rate, and C(H2O)
Serum ADH decrease
Serum osmolarity decrease
Urine = hyposmotic
Urine flow rate = high
C(H2O) = positive
Effect of central diabetes insipidus on serum ADH, serum osmolarity, urine osmolarity, urine flow rate, and C(H2O)
Serum ADH decrease
Serum osmolarity increased
Urine osmolarity = hyposmotic
Urine flow rate =high
C(H2O) = positive
Effect of nephrogenic diabetes insipidus on serum ADH, serum osmolarity, urine osmolarity, urine flow rate, and C(H2O)
Serum ADH increased
Serum osmolarity increased
Urine osmolarity = hyposmotic
Urine flow rate = high
C(H2O) = positive
Effect of water deprivation on serum ADH, serum osmolarity, urine osmolarity, urine flow rate, and C(H2O)
Serum ADH increased
Serum osmolarity high-normal
Urine osmolarity = hyperosmotic
Urine flow rate = low
C(H2O) = negative
Effect of SIADH on serum ADH, serum osmolarity, urine osmolarity, urine flow rate, and C(H2O)
Serum ADH INCREASED
Serum osmolarity decreased
Urine osmolarity = hyperosmotic
Urine flow rate = low
C(H2O) = negative
