4.4_2 Renal II Flashcards
Does the medulla have high or low osmolarity?
HIGH
Osmolarity =
Osmoles / liter
What is the osmolarity of 150 nM NaCl? (in most / L)
300
What is the medulla’s saltiness due to?
The countercurrent multiplier system in the Loop of Henle
Three essential features of the countercurrent multiplier system in the Loop of Henle
- Filtrate countercurrent
- Differential water permeability
- Countercurrent blood flow
Filtrate countercurrent
Tubular fluid flows in the opposite direction in descending and ascending limbs
Differential water permeability
Ascending and descending limb have different permeabilities to water
Is the ascending limb permeable to water?
No, it is thick and impermeable to water
What does the ascending limb do?
Actively transports ions out of the tubular fluid into the interstitial space
Is the descending limb permeable to water?
Yes, the entire limb is permeable to water
Countercurrent blood flow
Blood in vasa recta also flows in opposite direction to the tubular fluid
In the ascending limb, __________ transport NaCl at ________ membrane… drags NaCl out of filtrate across _______ into ________
ATP driven pumps
Basolateral
Tubule epithelial cells
Interstitial space
First step of counter current multiplier
Pumps Na+ from filtrate into surrounding interstitial space
Water can’t follow
Is filtrate entering the DCT dilute or salty?
Dilute
What happens with the vasa recite near the ascending limb?
Water from plasma chases salt into interstitial space, vasa recta plasma becomes saltier as it heads towards descending limb
Why does the water in filtrate move out in the descending limb?
Because it is
Chasing salt pumped out by ascending limb in interstitial space
Chasing salty blood in vasa recta
Vasa recta by the descending limb
Some salts leave chasing water from filtrate (adds salt to interstitial space)
What happens to the water left in the vasa recta
Re-enters blood, gets whisked aways to the heart
The combination of the Loop of Henle and vasa recta capillaries establish…
An osmotic gradient
What is the osmolarity of the interstitial fluid at the base of the Loop of Henle?
~1200 mOsmoles
-Super salty!
Is the filtrate salty or dilute at the base of the loop of Henle?
Very salty, but it does not matter because the salt will be extracted as it rises up the ascending limb
The filtrate is ~___mOsmoles ay the end of the Loop
100
Blood Osmolarity is regulated by…
Water retention (ADH)
Blood volume is regulated by
Retention of salts
Na, K (Aldosterone and Atrial Natriuretic Petide))
Sensor cells for osmolarity are in the…
Hypothalamus.. ADH neurons
Effectors for osmolarity regulation
The epithelial cells lining the collecting duct express ADH receptor
The hypothalamic cells release _____ which controls how _______ the ______ is to water
ADH
Permeable
Collecting duct
Hypothalamic _______ integrate signals for osmolarity
Osmoreceptors
ADH is produced in ________ cells in hypothalamus and released in _________
Neurosecretory
Posterior pituitary
_______ cells in collecting duct respond to ADH by increasing expression of _______
Principal Water channels (aquaporins)
Water deficit = _______ –> Stimulates high plasma _____ –> Promotes water reabsorption in ________
High osmolarity
ADH
Collecting duct
Do collecting ducts have more or less aquaporins open when ADH is expressed?
More, this makes it more permeable to water
Why does water leave the collecting duct and enter the interstitial fluid?
Because of the saltiness that the Loop of Henle creates
Water excess = ______, low plasma _____ –> Water lost to the urine
Low osmolarity
ADH
When ADH is not expressed, collecting ducts are _____ to water, causing..
Impermeable
Water to pass by the salty medulla
