Regulation of Sodium and Water Balance Flashcards
What are the low pressure CP circuit components
Cardiac atria and pulmonary vasculature
What are the high pressure arterial circuit components
Carotid sinus, aortic arch, JG apparatus
Total body sodium equals what
Dietary Na - urinary excretion
When ECF is low, what is Na excretion and retention?
Decreased; increased
When ECF volume is high, what is Na retention and excretion?
Decreased; increased
What factors serve to increase Na excretion
- dopamine
- ECF [Na] increase
- ECF volume increase
- Natriuretic peptides
What factors contribute to decrease Na excretion
- RAAS
- sympathetics
- ADH
What are the main functions of RAAS
Retain water
Retain Na
Kick K
What activates renal sympathetics
- constriction of afferent arterioles (decrease in GFR)
- increased tubular reabsorption of water and salt
- activated RAAS
What promotes renin secretion
- symp stim of JG by β1
- decreased NaCl delivery to macula densa
- afferent arteriole vasoconstriction
What inhibits renin secretion
- increased Na Cl reabsorption at macula densa
- increased afferent arteriole pressure
- ADH
- Ang II (negative feed back)
What does ang II stimulate
- efferent constriction more than afferent
- Na reabsorption in the PT (via NaH exchanger)
- increased thirst
- increased ADH secretion from post pit
- increased aldosterone secretion from adrenal cortex
What does Ang II do for reabsorption of Na in the LoH
Increases it
What does aldosterone cause at the DT
Increased Na reabsorption and increased K secretion
What intracellular receptor does aldosterone bind to
MR (mineralocorticoid receptor)
What transporter is produced in greater numbers in response to aldosterone
NaK ATPase and ENaC
How does aldosterone have the overall result of an increase in Na reabsorption and increase in K excretion
Increased synthesis and activity of NaK ATPase
Increased synthesis and activity of ENaC in apical membrane
What cells in the late DT and CD are responsible for increased Na and H2O reasborption and K secretion
Principal cells
What are the 3 ions affected by aldosterone
Na (increased reabsorption)
K and H (increased secretion)
Where are the most sensitive osmolality receptors
Hypothalamus and liver
What is ADH secretion more sensitive to
Increases in osmolality
What two things does ADH secretion rely on
Hyperosmolality and volume depletion
Where are the baroreceptors
Aorta and carotid sinus
What 3 main actions does ADH do
- Increases water permeability of principal cells by inserting more aquaporins
- Increases urea permeability in the inner medullary collecting ducts
- Increased the activity of the NKCC in the TAL
What does ADH bind to extracellularly
V2 receptor and functions through Gαs
What happens after ADH binds to its receptor
AQP2 (aquaporin) is inserted into the apical membrane
What happens when ADH levels decrease
AQP2 is endocytosed and recycled
Which AQP are unaffected by ADH levels? Where are they
3 and 4; they are on the basolateral membrane
Where are the osmoreceptors in the hypothalamus
OVLT and SFO
What is special about the OVLT and SFO
They are outside the BBB
What carries the signal from the brain osmoreceptors to the hypothalamus
Magnocellular neurons
Where is ADH released into circulation
Posterior pituitary
What things stimulate ADH secretion
Nausea, ang II, nicotine
What inhibits ADH secretion
ANP and EtOH
What are prostaglandins protective of
RBF
What buffers the vasoconstrictive effects of SNS/RAAS
Prostaglandins
What do NSAIDs lead to a retention of
Na because PGE2 is interfered with
What pts would we want to be careful when administering NSAIDs
HTN, renal stenosis, pts on diuretics
What increases ADH
- increased plasma osmolality
- decreased BP
- decreased BV
- nicotine
What decreases ADH
- decreased plasma osmolality
- increased BP
- increased BV
- EtOH
What increases thirst
- increased plasma osmolality
- decreased BP
- decreased BV
- increased Ang II
- mouth dryness
What decreases thirst
- decreased plasma osmolality
- increased BP
- increaesd BV
- decreased Ang II
- gastric distension
Where do ANP/BNP come from? What are they secreted in response to?
Atria and ventricles; increased stretch of cardiomyocytes
What does ANP/BNP do for Na and water
Promotes NaCl and water excretion
What change does ANP/BNP cause in GFR
Elevated
What action does ANP/BNP have on vessels
Systemic vasodilator
Where is urodilatin produced and what does it do
Kidney
Promotes NaCl secretion and have no effect on systemic vasoactivity
What do naturietic peptides generally oppose
RAAS, sympathetic NS, and ADH
What actions do natriuretic peptides cause on the kidneys
increased GFR, decreased renin, decreased aldosterone, decreased Na and H2O reabs in CD, decresed ADH
What stimulates secretion of ADH
- increased plasma osmolality
- decreased BV
- decreased BP
What stimulates secretion of PTH
- decreased plasma [Ca]
- increased plasma [PO4]
- decreased plasma [calcitriol]
What stimulates aldosterone secretion
- decreased BP
- decreased BV
- increased plasma [K]
What 4 responses does increased Na intake cause
- decreased sympathetic activity
- increased ANP
- decreased πc
- decreased RAAS
What does decreased Na intake cause
- increased sympathetic activity
- decreased ANP
- increased πc
- increased RAAS
What is the hemorrhage response
- RAAS activation
- sympathetic activation
- ADH release
- decreased Pa and baroreceptor response
- altered blood gases (chemoreceptor reflex)
Where is the JG apparatus
Distal convoluted tubule
