04b: Na Regulation Flashcards
(X)% of Na is in bone and not available for ordinary metabolic processes. Of the available Na, most, (Y)%, is in (Z).
X = 40; Y = 90; Z = ECF
Normal daily Na intake is about (X), but what’s the full range?
X = 100 mEq
Less than 1 mEq to over 400 mEq
Typical ICF:ECF volume ratio.
2:1
Major excretory pathway for Na is (X). How else, although in negligible amounts, is Na excreted?
X = renal excretion;
Sweat and stool
T/F: Regulation of body Na is primarily achieved by receptors that detect changes in osmolality.
False - detect changes in ECF volume/P (secondary to changes in Na content of ECF)
T/F: Increase in salt ingestion increases osmolality of ECF, but not ICF.
False - both (osmotic equilibration)
Following increased Na ingestion and compensatory mechanisms, a new steady state is reached. This includes (increased/decreased) volume by addition of (hypo/hyper/iso)-osmotic solution.
Increased;
Iso-osmotic
Effective Circulating Volume (ECV) is the (X) of blood that’s (Y). In other words, it’s a degree of filling of (Z).
X = pressure Y = perfusing the baroreceptors Z = arterial system
T/F: In all circumstances, ECV changes in parallel with ECF volume.
False - may be independent in some cases (ex: CHF)
Major baroreceptors involved in sensing of Na content by monitoring (X) are in which location(s)?
X = ECV
- Carotid sinus and aortic arch
- Atria (cardiopulmonary receptors)
- Afferent arterioles in kidney
How do baroreceptors in carotid sinus/aorta respond to increase in ECV?
Reduce symp NS signaling
How do baroreceptors in Atria respond to increase in ECV?
Release ANP
and can also alter symp NS
How do baroreceptors in afferent arterioles respond to increase in ECV?
Reduce renin secretion from JG apparatus
List the two general methods for adjustment in Na excretion by kidneys.
- Filtered Na load (determined mainly by GFR)
2. Tubular Na reabsorption
T/F: Renal processing of Cl is usually coupled to Na, so Na excretion regulation applies equally to Cl.
True
What’s the equation that determines Na filtrated by kidney? The typical daily value is:
P(Na)GFR = (140)(180) = 25,200 mEq/day
Aside from the proximal tubule, list the tubules that “fine tune” Na reabsorption.
Distal convoluted tubule and collecting duct
Increase in body Na leads to (increase/decrease) GFR. Explain.
Increase;
Increase in ECF and plasma volume
Decreased Na/ECF (increases/decreases) sympathetic innervation of (aff/eff) arterioles, thus having which effect on GFR?
Increases (vasoconstriction);
Afferent;
Reduces GFR
(Increased/decreased) Na/ECF leads to release of (X), which leads to increased GFR by (vasodilation/vasoconstriction) of (aff/eff) arterioles.
Increased;
X = ANP and NO
Vasodilation of aff and vasoconstriction of eff
T/F: Changes in GFR are required to maintain Na balance.
False - tubular reabsorption can maintain GT balance
T/F: Tubular reabsorption, not GFR changes, is the main response to ECV fluctuations.
True
Which transporters are responsible for Na (uphill/downhill) exit from basolateral membrane? Star the one that’s more important.
Uphill;
- Na/K ATPase*
- (3)HCO3/Na
At the early proximal tubule, preferential mode of Na entry into tubular cells is via which transport method?
Co-transport with organic solutes;
and some H+ exchange
At the late proximal tubule, which two (co-transporters/exchangers) are coupled?
Exchangers;
NaH and Cl-OH
Cl reabsorption occurs in (early/late) proximal tubule and is (co-transported/exchanged) with (X).
Late ;
Exchanged;
X = OH
(Passive/active) Na reabsorption takes place in TAL of loop of Henle.
Passive (paracellular)
TAL Na reabsorption involves (cotransport/exchange) with (X).
- Co-transport
X = K and (2) Cl - H+ exchange
In early distal tubule, Na reabsorption is (cotransported/exchanged) with (X).
Co-transported;
X = Cl
Late distal tubule and collecting duct Na reabsorption via which transporter?
Epithelial Na channel
Euvolemia is condition in which (X) is/are normal.
X = ECF volume and Na content
List the four regulatory mechanisms that alter fraction of tubular Na reabsorbed proximally in response to ECF changes.
- Sympathetic nerves
- AII
- Starling forces in peritubular cap’s
- NO
T/F: Sympathetic nerves directly innervate proximal tubule and inhibit Na reabsorption.
False - stimulate reabsorption (by stimulating Na-H exchanger)
NO, stimulated by volume (expansion/contraction) will (stimulate/inhibit) Na reabsorption.
Expansion;
Inhibit
List two regulatory mechanisms that alter fraction of tubular Na reabsorbed in TAL in response to ECF changes.
- ADH (stimulatory)
2. Prostanoids and NO (inhibitory)
Prostanoids and (X) are released by (Y) cells in TAL and (increase/decrease) Na reabsorption.
X = NO
Y = tubular and medullary interstitial;
Decrease
In euvolemic conditions, (X) is the primary regulatory of Na reabsorption by its effects on (proximal/distal) segments of nephron.
X = aldosterone
Distal
Aldosterone is a(n) (X), released by (Y) cells of (Z).
X = steroid hormone; Y = glomerulosa Z = adrenal cortex
T/F: Plasma level of renin is rate-limiting factor in series of events leading to aldoesterone production.
True
Angiotensinogen is produced by (X) and cleaved by (Y), produced by (Z).
X = liver Y = rening Z = JG cells
Aldosterone acts on (X) cells of distal nephron by binding (lumenal/basolateral) receptor. (Activation/inhibition) of this receptor leads to:
X = principal
CYTOPLASMIC
Activation;
Translocates to nucleus and regulates gene transcription
Early effects of aldosterone on distal nephron involve (X), causing (increase/decrease) in Na reabsorption.
X = recruitment of apical Na channel and basolateral NaK ATPase
Increase
Later effects of aldosterone on distal nephron involve (X), causing (increase/decrease) in Na reabsorption.
X = increased synthesis of Na transport proteins
Increase
Secretion of renin by (X) cells involves process that’s activated by (Y), which is stimulated by (Z).
X = JG Y = protein kinase A Z = cAMP
High intracellular Ca has which effect on renin secretion? Explain.
Decrease;
Inhibits adenylate cyclase in JG cells, thus decreasing cAMP then PKA activity
List three distinct inputs to JG cells that increase renin secretion in response to (low/high) ECF/Na volume.
Low;
- Symp nerve activity
- Low perfusion pressure
- Low NaCl delivery to macula densa
Sympathetic nerve activity on JG cells: (X) NT binds (Y) receptor and (increases/decreases) (Z) activity.
X = NE
Y = beta-1 adrenergic
Increases;
Z = AC
High perfusion pressure in (aff/eff) arteriole is sensed by intrarenal baroreceptors. This (increases/decreases) renin secretion by (increasing/decreasing) (X) of JG cells.
Aff;
Decreases;
Increasing;
X = intracellular Ca levels (inhibits AC)
The volume of water reabsorbed by the descending limb (increases/decreases) with high ADH, aka (diuretic/antidiuretic) state.
This happens because:
Osmotic driving force (interstitial osmolality) is larger in antidiuresis (1200 mOsm);
NOT because ADH affects the permeability to water of this segment
How does state of diuresis differ in case of ingesting large amounts of water versus taking diuretic?
Taking diuretic will increase both solute and water excretion; ingesting large amount of water will result in increased excretion of primarily water
T/F: Addition of water to the body usually causes a permanent increase in ECF
volume.
False
T/F: Addition of water to the body usually causes a permanent increase in BP.
False
T/F: Most of water retained/reabsorbed is usually added to ICF.
True
