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63 Cards in this Set

  • Front
  • Back
What is the osm of isotonic urine and what is its rate of production?
300 mOsm
What is the osm of hypotonic urine, what condition will cause its production, and what is its rate of production?
100 mOsm


What is the osm of hypertonic urine, what condition will cause its production, and what is its rate of production?
1200 mOsm


0.3 ml/min
What does Obligatory Water Loss
Body must lose a certain amount of water regardless of level of hydration.
What happens when the renal threshold [] is exceeded?
Solute will be excreted into urine
Na+ reabsorption in the ALofH:
What reabsorption occurs in the ALofH and how is it transported?
K+ and Cl-

Brought through via facilitated diffusion (active process)
Na+ reabsorption in the DT and its symporter:
Na actively pumped out; Cl-
Na+ reabsorption in the CD:
Na moves in passively; Na is pumped out
What determines passive Na+ channels in DT & avail of symporters in DT?
Presence of Aldosterone
Na+ follows H20 or H2O follows Na+?
H2O follows Na+
What creates the osm gradient for H20 passive reabsorption?
Movement of Na+
What's the driving force for H2O?
Osm gradient
What is the paracellular route for Na+ Coupled Passive Water Reabsorption and what allows the Na+ in?
In between "leaky" epith cell junctions

ATPase pumps on the lateral spaces
How much H2O is reabsorped in the proximal tubule and the loop of henle?
80 %
What allows H2O to reasbsorp transcellularly, where are they found, and what is limiting factor?
The presence of ADH creates aquaporins

Found basolaterally

Amount of aquaporins and hence levels of ADH
What regulates [plasma] of PO43- and Ca2+?
Renal threshold absorption
What is the only waste product that's reabsorped?
How much Na+ & Cl- and H2O are reabsorped in LoH?
25% and 15%
What important substances are secreted?
Hydrogen ions, potassium ions,
and organic cations and anions (usually foreign to the body)
What role does H+ secretion play and where does it prim. occur?
Helps with pH balance and in the PT and CD
How is H+ secretion accomplished in PT?
Na+/H+ antiporter
How is H+ secretion accomplished in CD & LoH?
Facilitated diffusion
K+ is actively secreted where?

What is the mechanism?

How is the level determined?

K+ secretion is coupled to Na+ reabsorption

(levels determined by aldosterone)
Which is regulated, K+ reabsorption or secretion?
If plasma [K] is low – secretion is __________
K+ is reabsorbed via passive diffusion where?
Where are K+ channels located on the luminal membrane and what does that mean?
In the DT and CD

It means it can enter tubular lumen
What effect does aldosterone have on Na+ reabsorption and K+ secretion?
opens luminal Na+ Channels (fast effect)

increases Na+/K+ ATPase expression (slow effect)
What are the two reasons for a pathway for Organic Anion and Cation Secretion?
Some of these ions can be bound to plasma proteins
and are never filtered by the glomeruli

2) Increase the speed of elimination
What does the medullary osmotic gradient do and what anatomical arrangement creates it??
plays a key role in the kidneys ability
to produce urine of varied concentrations

Medullary Countercurrent System
What makes up the Medullary Countercurrent System and which sets osmotic gradient?
LoH, DT, & CD

What structure prevents dissipation of osmotic pressure and how does it work?
Vasa recta

reduces surface area available for exchange between HGb and IS fluid
DLoH is Permeable to ____ and Impermeable
to ____
H2O; Na+
ALoH is Permeable to ____ and Impermeable
to ____
Na+; H20
Difference in permeability of ALoH and DLoH causes _______ creating _______; this is called _______
countercurrent multiplication

osmotic gradient

countercurrent flow
ADH affects H2O permeability in _______ & ________
ADH is synthesized in the _______
Vasopressin works by binding to receptors on the _______ increasing ______ and creating ______
basolateral membrane


Regulation of ECF _______ helps maintain ___________ and therefore tissue perfusion.

Regulation of ECF __________ helps maintain cell ________

How does the body regulate ECF volume?
by regulating total-body salt content
What's the main osmotic constituent of ECF volume?
Is the relationship between Na+ & H2O gain/loss inverse or linear?
What are the two mechanisms for NaCl loss?
Renal excretion

Nonrenal loss (sweat and feces)
How is Na+ gained?
Through ingestion
How does the body monitor ECF volume? What kind of receptors are involved in this? What are they?
Through changes in BP that have a direct effect on plasma volume

Aortic Arch baroreceptors
Carotid Sinus baroreceptors
Renal baroreceptors
What act as renal barorecptors?
Granular cells
What is the sequence of events when the JGA baroreceptors sense a drop in blood pressure?
The liver produces Angiotensiogen, which is converted by renin released from the kidneys, which converts
How is total-body osmolarity defined?
the ratio of total-body osmoles
to total-body water
How is total-body osmoles determined?
ECF Na+ content
What are two sources for water gain?

liberated from metabolic processes
What are three sources for water loss?


What elements control osmolarity?
the kidneys control of water excretion

the thirst mechanism that controls oral intake of water
Are the mechanisms that control osmolarity a negative or positive feedback loop? Where do they originate?

What is the name for the two central osmoreceptors collectively? What are they individually?
Circumventricular Organs (CVOs)

Subfornical Organ (SFO)& Organum vasculosum of the lamina terminalis (OVLT)
Where are the CVOs?
Outside the blood-brain barrier
What happens when the CVOs detect high osmolarity?
Increase firing rate, stimulate neurosecretory cells in teh SON & PVN, signal to the posterior pituatary which then releases ADH
What is the plasma osmolarity in healthy individuals? What is the threshold for AVP release?
290 mOsm

280 mOsm
What happens when mOsm drops below threshold? What is the relationship between ADH levels and osmolarity?
CVOs stop secreting ADH (over-hydration)

Where does ADH act?
On the DT & CD to increase H2O reabsorption
Baroreceptors will also cause activation of the _________ resulting in ________
hypothalamus neurosecretory cells; thirst
What effect does EtOH have on plasma [ADH}?
Decreases it