74: Conc. & Dilution of Urine Flashcards
What happens during dehydration?
Increase in plasma osmolarity (concentrated)
What happens during over hydration?
Decrease in plasma osmolarity (diluted)
What receptors in the anterior hypothalamus are stimulated or inhibited to normalize plasma osmolarity?
Osmoreceptors
Hyperosmotic urine
Osmolarity higher than plasma osmolarity (300 mOsm/L)
Hypoosmotic urine
Osmolarity lower than plasma osmolarity (300 mOsm/L)
Which components of nephron control dilution/concentration of urine?
Ascending loops
Late distal tubule
Collecting duct
What is the osmotic gradient of urine?
300 – 1200 mOsm/L
What is the interstitial osmolarity of the cortex?
Isosmotic
300 mOsm/L
What is the interstitial osmolarity of the medulla?
Hyperosmotic
600 or 1200 mOsm/L
What two processes that contribute to corticopapillary osmotic gradient?
Countercurrent multiplication
Urea recycling
What factors generate and maintain the Osmotic Gradient?
ATP-dependent solute transport
Increase in osmolarity in medullary interstitium
Slow tubular fluid flow
Which ions are actively removed in the thick portion of the ascending limb?
Na+ & Cl-
How do Na+ & Cl- leave in the think ascending limb?
Diffusion
____ moves from
descending limb to
equilibrate increasing
interstitial concentrations
H2O
What part of the nephron concentrates the filtrate?
Loop of Henle
Countercurrent Exchanger in Vasa Recta
Passive - no energy
Return solute and H2O back to circulation
Which hormone is released during dehydration?
ADH
Where is ADH released from?
Posterior pituitary
What does ADH do in the nephron?
Increases H2O permeability in the distal tubules and collecting ducts
Increases H2O reabsorption into blood
Decreases urination frequency
Urine more concentrated
What is another name for ADH
Vasopressin
Which parts of the nephron are ADH dependent?
Late distal tubule
Cortical collecting duct
Outer medullar collecting duct
Inner medullary collecting duct
Low ADH does what to urine flow rate?
Increases (High flow rate)
High ADH does what to urine flow rate?
Decreases (Low flow rate)
Syndrome of inappropriate antidiuretic hormone
SIADH
Defect or damage to the thirst mechanism in the hypothalamus resulting in abnormal increase in thirst and fluid intake that suppresses
ADH secretion and increases urine output
Dipsogenic diabetes insipidus
only occurs during pregnancy where mothers produce vasopressinase in the placenta, which breaks down ADH
Gestational diabetes insipidus
Recirculation of Urea
ADH dependent
Urea reabsorbed into interstitial then secreted back into ascending limb
What are the urea transporters on the collecting duct?
UT-A1 & UT-A3
What contributes to half of the interstitial gradient at the base of Loop of Henle?
Urea (600 mOsm)
If no ADH is present then what is the interstitial gradient at the Loop of Henle?
600 mOsm because urea is not contributing
Clearance of Urea when ADH present
low urea excretion & low urine flow rate
Clearance of Urea when NO ADH present
high urea excretion & high urine flow rate
How does urea move?
Passive transport
What increases Na+/K+/Cl transporter effectiveness?
ADH
