Module 5.11 Renal Handling of Water Flashcards
The osmolarity of the extracellular fluid (ECF) is dependent on _____________
The osmolarity of the extracellular fluid (ECF) is dependent on the concentration of water
When is ECF isotonic?
ECF is isotonic at an osmolarity of 300mosm/L when normal fluid balance and solute concentrations are present
Hypotonic conditions refer to an osmolarity _____\_than 300 mosm/L; hypertonic conditions refer to an osmolarity ___\_ than 300 mosm/L.
Hypotonic conditions refer to an osmolarity greater than 300 mosm/L; hypertonic conditions refer to an osmolarity less than 300 mosm/L.
Normally, there is no osmotic force for water to move between the fluid compartments of the body because ECF osmolarity is regulated by the ______\_ of water.
Normally, there is no osmotic force for water to move between the fluid compartments of the body because ECF osmolarity is regulated by the renal handling of water.
In the _____\_ tubule, water is reabsorbed passively using the osmotic gradient established by the active transport of ____. This accounts for approx ___% of reabsorbed water
In the proximal tubule, water is reabsorbed passively using the osmotic gradient established by the active transport of Na+
This accounts for approx 80% of reabsorbed water
In the _________\_, the remaining water can be reabsorbed through regulated mechanisms involving the hormone ______\_ and the ______\_________\__ system (multiplier).
In the collecting ducts, the remaining water can be reabsorbed through regulated mechanisms involving the hormone vasopressin and the medullary countercurrent system (multiplier).
The osmolarity of the interstitial fluid in the medulla varies with ____\_.
Osmolarity is lower near the ____\_and higher near the ______\_.
This is referred to as the ____ ______\_ gradient.
The osmolarity of the interstitial fluid in the medulla varies with depth.
Osmolarity is lower near the cortex and higher near the renal pelvis.
This is referred to as the vertical osmotic gradient.
The vertical osmotic gradient is established and maintained by the ______ ______\_system formed by the ________\_ in _______\_ nephrons.
The vertical osmotic gradient is established and maintained by the medullary countercurrent system formed by the loop of Henle in juxtamedullary nephrons.
The descending limb of the loop of Henle, which extends deep into the renal medulla, is ____\_to water, but ____\_ to ions.
In contrast, the ascending limb of the loop of Henle is ____\_to water, but ____\_ to the ions: __\_and __\_.
As the filtrate passes through the loop of Henle, its composition is modified accordingly.
The descending limb of the loop of Henle, which extends deep into the renal medulla, is permeable to water, but impermeable to ions.
In contrast, the ascending limb of the loop of Henle is impermeable to water, but permeable to the ions: Na+ and Cl-.
As the filtrate passes through the loop of Henle, its composition is modified accordingly.
Water reabsorption in the collecting ducts is dependent upon the _________\_established by the _______\_ system and the permeability of the _______\_ to water
Water reabsorption in the collecting ducts is dependent upon the osmotic gradient established by the countercurrent system and the permeability of the epithelium to water
_________-__\_(water channel) is always present in the basolateral membrane of the tubular epithelial cells
Aquaporin-3 (water channel) is always present in the basolateral membrane of the tubular epithelial cells
Aquaporin-3 (water channel) is always present in the _______\_ membrane of the tubular epithelial cells
Aquaporin-3 (water channel) is always present in the basolateral membrane of the tubular epithelial cells
The hormone _______ is responsible for the insertion of aquaporin-2 in the apical membrane
The hormone vasopressin is responsible for the insertion of aquaporin-2 in the apical membrane
the insertion of ______\_ in the apical membrane is dependent upon the hormone vasopressin
the insertion of aquaporin-2 in the apical membrane is dependent upon the hormone vasopressin
In the absence of vasopressin and thus aquaporin-2, the collecting duct is impermeable to water.
In this case, would reabsorption occur?
In the absence of vasopressin and thus ________\_, the collecting duct is impermeable to water.
No reabsorption occurs
Water reabsorption in the late distal tubule and collecting duct:
(Left) When the membrane of the late distal tubule and collecting duct is impermeable to water, water cannot leave the tubule and is excreted in the urine. This produces a ___\_volume of urine with ___\_ osmolarity.
(Right) When the membrane of the late distal tubule and collecting duct is permeable to water, water can leave the tubule and be reabsorbed. This produces a ___\_volume of urine with ___\_ osmolarity.
Water reabsorption in the late distal tubule and collecting duct:
(Left) When the membrane of the late distal tubule and collecting duct is impermeable to water, water cannot leave the tubule and is excreted in the urine. This produces a high volume of urine with low osmolarity.
(Right) When the membrane of the late distal tubule and collecting duct is permeable to water, water can leave the tubule and be reabsorbed. This produces a low volume of urine with high osmolarity.
Vasopressin binds to plasma membrane receptors in the ____\_membrane of tubular epithelial cells in the _____ ____\_ to cause the ____\_of _____\_ into the ____\_ membrane, as shown in the following mechanism
Vasopressin binds to plasma membrane receptors in the basolateral membrane of tubular epithelial cells in the collecting duct to cause the insertion of aquaporin-2 into the apical membrane, as shown in the following mechanism
Mechanism of action of vasopressin:
Vasopressin binds to its receptors on the _____\_membrane of __\_ and ____\_ tubule cells.
This binding activates the ____ ____ ______\_system which increases the _____\_ of _____ _________\_ in the luminal membrane, thus increasing the permeability of the luminal membrane to H2O.
Mechanism of action of vasopressin:
Vasopressin binds to its receptors on the basolateral membrane of distal and collecting tubule cells.
This binding activates the cyclic AMP second-messenger system which increases the insertion of water channels (aquaporin-2) in the luminal membrane, thus increasing the permeability of the luminal membrane to H2O.
