Flashcards in Unit 2 Deck (276)
Cells of the body depend on..
A constant interstitial fluid concentration of solutes and osmolarity
-this is regulated by controlling the amount of extracellular water there is
Osmolarity is regulated by...
Water intake (thirst)
Renal excretion of water (glomerular filtration and reabsorption)
EDF osmolarity is about..
Kidneys can excrete urine that ranges from..
50 mOsm/L - 1200 mOsm/L
How can the kidneys eliminate excess water?
How do they conserve water?
Can produce copious amounts of dilute urine
Can produce small amounts o concentrated urine
(Both can be done without changing excretion rates of solutes)
ADH regulates _____ (and therefore ___) ____ by controlling:
Plasma (and therefore interstitial) osmolarity
What happens what plasma osmolarity is increased?
Post pituitary ADH secretion increases
Distal tubule H2O permeability increases
Water reabsorption increases
As urine osmolarity changes, what happens to plasma osmolarity?
There is little to no change
Proximal tubule’s job in diluting urine
Solutes and water are reabsorbed at equal proportions (isosmotic)
Absorption of water in the descending loop of henle is due to:
a higher concentration of solutes in the renal medulla interstitium
The descending loop of henle concentrates what?
The tubular fluid (hyperosmotic)
In forming a dilute urine, what happens in the ascending loop of henle (thick)?
Reabsorption of electrolytes (Na+, K+, Cl) but not water
Dilutes tubular fluid (hyposmotic)
*this part of the loop is NOT permeable to water*
ADH is ____ in distal and collecting tubules when forming dilute urine. This means:
There is no reabsorption of water
The renal handling of water changes to form concentrated urine by the presence of:
What does ADH do in the distal and collecting tubules to H2O?
Increases permeability to H2O
Causes reabsorption of water and a concentrated (hyperosmotic) urine
-since the renal medulla interstitium is hyperosmotic
A concentrated urine depends on _____ and:
A hypertonic renal medullary interstitium
Review slide 9
The most concentrated urine can be is:
The min amount o metabolic wastes and excess ions that must be eliminated bu the body to maintain homeostasis is about:
The minimal amount of urine one must form a day is:
600/1200 = .05 L/day
What causes the renal medulla to become hyperosmotic ?
The countercurrent multiplier system
6 general steps of the countercurrent multiplier
1- the tubule fills with isosmotic fluid, with all transport systems/permeabilities off
2- ascending Limb pumps turned on— Increases osmolarity of the medulla
3- water permeability of the descending limb turned on. Causes equilibrium between the descending limb and the medulla interstitium (interstitium stays hyperosmotic bc the ascending pumps are still on)
4- tubular flow turned on. The hyperosmotic fluid that was in the descending limb moved to the ascending limb
5- the ascending limb still reabsorb solutes further concentrating the medially interstitium
6- the descending limb loses more water by osmosis again
*steps 4-6 are repeated to create a max gradient through the interstitium*
Review slide 15
What are impermeable to urea?
The ascending limb, distal tubule, and cortical collecting duct
What is permeable to urea? And what increases this?
Medullary collecting duct
As urine concentrates with ADH, ____ also concentrates, and is therefore (ACTIVELY/PASSIVELY) reabsorbed into the ____ contributing to:
Urea reabsorbed into the ___ ____ __ is secreted into the:
Medullary collecting duct
Loop of henle
Recirculates increasing its concentration
In the presence of ADH, Urea recirculating (INCREASES/DECREASES), helping to maintain:
Hyperosmolarity of the renal medulla
In the absence of ADH, (MORE/LESS) urea is excreted