04a: Osmoregulation Flashcards
T/F: Normally, water is reabsorbed iso-osmotically at proximal tubule.
True
ADH, secreted by (X), primarily affects (Na/water)-permeability in (Y) portion of tubule.
X = posterior pituitary;
Water;
Y = collecting duct
High plasma ADH: you’d expect excretion of (high/low) volume of (dilute/concentrated) urine.
Low; concentrated
About (X)% of water is reabsorbed in thick descending tubule.
X = 23
Classic experiments of Verney demonstrated that plasma (hypo/hyper)-osmolality results in (X) with resultant (increase/decrease) of (Y).
Hyper-osmolality;
X = prompt secretion of ADH
Decrease;
Y = urine volume (with increase concentration)
Creation of osmotic gradients occurs largely in which part of tubules? Why?
Ascending limb of loop of Henle;
Salt is actively reabsorbed, without transport of water
The osmolality gradient is 200 mOsm at each level between which spaces?
Lumen of TAL (200 mOsm less) than interstitium and lumen of DL
There’s a progressive (increase/decrease) in osmolality as tubular fluid flows downward toward hairpin loop. and (increase/decrease) in osmolality as it travels back upward.
Increase;
Decrease
T/F: The osmolality in the inner medulla is primarily, 80%, due to Na.
False - mainly salt, but urea can contribute up to 50%
A (low/high) protein diet is known to markedly depress renal concentrating ability due to (deficit/excess) in (X).
Low;
Deficiency;
X = urea
T/F: Urea is a minor solute of voided urine, since large fraction undergoes medullary recycling.
False - major solute of voided urine, despite this recycling
Medullary recycling of urea takes place in which tubule? The solute goes from (X) into (Y).
Inner medullary collecting duct;
X = IMCD
Y = interstitium THEN thin ascending loop of Henle
During diuresis, (low/high) rate of water reabsorption results in (low/high) concentration of urea presented to terminal IMCD.
Low; low
(X) enhances IMCD urea permeability. You’d expect this to be the result of (diuretic/antidiuretic) state.
X = ADH;
Antidiuretic (high urea concentration in IMCD)
In (diuretic/antidiuretic) state, urea’s contribution to interstitial osmolality is greatest, nearly (X)%.
Antidiuretic (high ADH);
X = 50
T/F: In the absence of ADH, the distal tubules and collecting ducts are impermeable to water.
True
Per day, the two extremes of total urine output are (X) in diuresis state and (Y) in antidiuresis state.
X = 18 L (10% GFR) of 50 mOsm conc Y = 0.4 L of 1200 mOsm conc
In brief, ADH binds (lumenal/basolateral) receptors that lead to (X) (activation/inhibition) which causes (increase/decrease) in (Y) formation.
Basolateral; X = AC Activation; Increase; Y = cAMP
In high ADH state, how does (increase/decrease) in cAMP alter collecting duct permeability?
Increase;
Phosphorylates lumenal membrane proteins that leads to increased aquaporin incorporation in lumenal membranes
T/F: ADH’s effects are confined to collecting duct permeability.
False - also acts on ascending limb Na transport and vasa recta blood flow
High ADH state: TAL Na transport would (increase/decrease) and vasa recta blood flow would (increase/decrease). Provide brief explanations.
Increase (facilitates water reabsorption by increasing interstitial osmolality);
decrease (reduce washout of interstitial solute)
Blood flow through the medulla tends to dissipate interstitial osmolality gradients. (X) phenomenon between (Y) structures counteracts this.
X = countercurrent exchange (of solutes and water) Y = ascending and descending limbs of vasa recta
ADH-secreting neurons receive (stimulatory/inhibitory) inputs from which main receptors? Star the more sensitive receptors.
- Osmoreceptors (stimulatory)*
2. Baroreceptors and cardiopulmonary receptors (inhibitory)
ADH: (osmo/baro)-receptors take precedent if there’s large change in (osmolality/volume). This could lead to (X) value that’s well below normal.
Baroreceptors;
Volume (greater 10% depletion);
X = osmolality
(Renin/AII/ANP) directly (stimulates/inhibits) ADH secretion.
AII stimulates; ANP inhibits
T/F: Osmoreceptors can be found in nearly all arterioles.
False - osmoreceptors are nearposterior pituitary neurons
T/F: Osmolality is the chief factor regulating secretion of ADH.
True
Oxidative metabolism contributes to our water (input/output).
Input
AQP1 present at (lumenal/basolateral) membranes of which duct?
Both; PT
T/F: Some aquaporins are present independently of ADH.
True - AQP3 and 4
Our obligatory water loss is around (X) per day.
X = 0.5 L
Where are the JG cells anyway? They’re actually specialized (X) cells.
Afferent arteriole wall
X = smooth muscle
