Kidney- water balance Flashcards
In order to maintain proper fluid balance, the kidney has the ability to excrete either a ___ urine to eliminate excess water, or a ____ urine to conserve water
dilute
concentrated
Antidiuretic hormone and aldosterone act on the kidney to regulate blood ____ and increase blood ____
osmolarity
volume
Natriuretic hormones (ANP, BNP, …) act on the kidney to stimulate ____ and decrease blood volume
diuresis
volume
3 ways we gain water:
drinking
food
metabolism
four ways we lose water:
urination
defecation
respiration
sweat
([Na+] + [K+]) − ([Cl−] + [HCO3−])
this represents:____
Anion gap
__% of Body weight is water
~___ L/day of water filtered (48 gallons!)
Water must be ___ to prevent dehydration
60
180
reabsorbed
____% of water is reabsorbed by PT
Hyperosmotic interstitial fluid (___ mOsm/L)
Hyposmotic tubular lumen (___ mOsm/L)
Osmotic pressure difference drives water to be ____
65-80
293
287
reabsorbed
Water is reabsorbed by ____ and mostly follows sodium
osmosis
PCT: ~__% H2O reabsorbed
Loop (descending limb): ~__% H2O reabsorbed
DCT: ~____% H2O reabsorbed
Late DCT & collecting duct: ~____% H2O reabsorbed (stimulated by ___) (reabsorbed with the Na+ & Cl- stimulated by ___)
65 15 10-15 5-10 ADH aldosterone
___ hydrostatic pressure and ___ oncotic pressure in peritubular capillaries favors water reabsorption
Low
high
The Loop of Henle:
Consists of a thin descending limb, permeable to ___
Sharp turn is permeable to ___ (recycles urea)
Thick ascending limb has ___ permeability to water and does Transport of _____
water
urea
Low
Na 2Cl K
~___% of water is reabsorbed by Loop
15
Countercurrent mechanism:
Descending loop of Henle
Water ____
↑____ in tubular lumen
Ascending loop of Henle
↓___ cytosolic (due to Na+-K+-pump)
Na+, K+, 2 Cl- (Symport)
Other Cations - ___++, ___++, etc.
Vasa recta – carries __ and___ into medulla and water out to the cortical veins
reabsorption [NaCl] [Na] Mg++, Ca++ Na+ & Cl-
active salt transport out of the water-impermeant thick ascending limb established a ____ gradient of about 200 mOsm/kg H2O between the tubular fluid and the medullary ISF
horizontal
The increased salt and osmotic concentration of the medullary ISF causes ___ to move into the descending limb and ___ to move out.
Both increase the osmotic concentration of tubular fluid
The small horizontal gradient is multiplied longitudinally by the ____ flow arrangement
salt
water
countercurrent
In the _____ vasa recta, blood coming down into the medulla from the cortex comes into contact with the concentration medullary ISF. ___ diffuses from that ISF into the blood increasing plasma concentration.
descending
Salt
In the ___ vasa recta, concentrated blood flowing up towards the cortex from the papilla loses ___ to the more dilute medullary ISF. Thus the salt, reabsorbed from the loop of henle, is trapped and recycled within the medulla by countercurrent flow of blood in the vasa recta.
ascending
salt
In the descending vasa recta, the dilute blood thats flowing into the medulla loses __ to the concentrated medullary ISF
water
In the Ascending vasa recta, the concentrated blood flowing from the tip of the papilla towards the cortex gains ____ from the medullary ISF.
Thus ____ tends to short-circuit from the descending to the ascending vasa recta.
This helps preserve the concentration of the medullary ISF
water
water
the descending limb is ___ permeable and has no ___ pump
water
Na
the ascending limb is not ___ impermeable but contains ___ pump
water
Na
___ and ___ are reabsorbed from filtrate in the ascending limb
Reabsorption of salt without water in the ascending limb makes the tubule fluid ___
Na+ and Cl-
dilute
the vasa recta & descending limb carry the salt back into the medulla to create and maintain a ___ osmotic pressure of the medulla’s interstitial fluid
high
Urea participates in the mechanism that maintains a ___ osmotic pressure
Osmotic pressure increases deeper into the ___
high
medulla
___ ____ mechanism of the loop of Henle and vasa recta creates the medullary osmotic gradient that allows the production of a concentrated urine
Countercurrent multiplier
Loop diuretic – major effect in the ___ ascending limb
Blocks ____ Symport
thick
Na+/K+/2Cl-
Furosemide effect in the thick ascending limb results in:
Decreased ___ reabsorption
Decreased ___ reabsorption
Decreased potential in lumen (less ___)
Decreases ___ mechanism for cation reabsorption; loss of K+, Ca+ + & Mg+ +
NaCl
K+
positive
paracellular
What hormones Increase blood volume?
Aldosterone (RAASystem)
Anti-diuretic Hormone (ADH)
What hormones Decrease blood volume?
Natriuretic peptides
The 3 types of Natriuretic peptides that decrease blood volume are:
Atrial natriuretic peptide (ANP)
B-type natriuretic peptide (BNP)
C-type natriuretic peptide (CNP)
Natriuretic peptides (ANP & BNP) increases ___
GFR
what causes the hormonal release when theres an increased in blood volume?
stretching of the atria & ventricles
Natriuretic peptides (ANP & BNP) increases GFR.
_______ may relax glomerular mesangial cells increasing capillary surface area and increasing GFR
Vasodilator
In hormonal regulation, what maintains GFR?
Angiotensin II maintains GFR
How does angiotensin II maintain GFR?
via potent vasoconstrictor that narrows the efferent arteriole more than afferent, maintaining GFR when BP is reduced
Hormone released from cardiac muscle cells when atrial blood pressure increases (also BNP from ventricles) is
Atrial Natriuretic Peptide (ANP)
What inhibits the release of Aldosterone & ADH
ANP
What are some of the effects of ANP
Causes Vasodilation
Simulates increased urine output
Produces a Decrease in blood volume and blood pressure
Inhibits aldosterone and ADH release
Vascular Smooth Muscle Regulation:
Decreased Ca++ or increased cAMP or cGMP inhibits ____ and/or stimulates ___ _____ which produces smooth muscle relaxation
MLCK
MLC phosphatase
What Increases kidney sodium/water reabsorption & decreases urine volume and increases blood volume?
Renin-Angiotensin-AldosteroneSystem
a proteolytic enzyme released by the juxtaglomerular cells of the kidney
Renin
____ cleaves angiotensinogen to Angiotensin-I
renin
This enzyme removes two amino acids from Angiotensin-I to produce Angiotensin-II
Angiotensin converting enzyme (ACE)
____ causes vasoconstriction and stimulates aldosterone & ADH
Angiotensin-II
The RAAS system consists of:
renin
angiotensin
aldosterone
What inhibits/prevents renin from converting angiotensinogen to angiotensin I
serine protease inhibitor
Where is aldosterone produced?
adrenal cortex of the adrenal gland
80-90% of the Cortex is derived from ___ – produces and secretes Steroid hormones
mesoderm
10-20% of the Medulla is derived from ___ - produces and secretes Catecholamines
ectoderm
what produces and secretes catecholamines in the adrenal gland?
medulla
what produces and secretes steroid hormones in the adrenal gland?
cortex
what is the primary mineralocorticoid produced by the cortex of the adrenal gland?
aldosterone
Aldosterone Increases reabsorption of __+ in the distal tubule and collecting ducts of the kidney
___,___, and ___ follow sodium (water retention)
Promotes excretion of K+ and H+
Na
Water, Cl-, and bicarbonate
___ hormones are synthesized by enzymatic modification of cholesterol by a series of cytochrome P450 enzymes (and one dehydrogenase) in the ___ and ___ of steroid hormone producing cells
Steroid
mitochondria
ER
Aldosterone synthesis (steps)
cholesterol —- progesterone —- corticosterone —- aldosterone
Aldosterone release is Increased by:
Angiotensin II
increased potassium blood levels
ACTH (minor) & decrease plasma sodium
Aldosterone release is Decreased by:
Atrial Natriuretic Peptide (ANP)
Dopamine
antihypertensives that work by directly inhibiting renin
aliskiren