1. Intro and Review Flashcards
intracellular compartment: what portion of total body water? what are Na and K concentrations?
8/12 total body fluid (or 2/3). Low Na: 10. High K: 150.
Plasma volume: what portion of total body water? what are Na and K concentrations?
1/12 total body fluid. High Na: 140, Low K (4)
Interstitial volume: what portion of total body water? what are Na and K concentrations?
3/12 total body fluid. High Na: 140, Low K (4)
what is the primary osmole in intracellular compartment?
K+
what is the primary osmole in extracellular compartments?
Na+
1200cc of water: how will it distribute?
800 to intracellular
300 to interstitial
100 to plasma
1200cc of 0.9% NaCl solution: how will it distribute? (isotonic to plasma)
900 to interstitial
300 to plasma
None to intracellular (NO osmotic gradient)
1200cc of KCl solution: how will it distribute? (assume isotonic to plasma)
all to intracellular.
none to interstitial
none to plasma
1200cc of 0.45% NaCl solution: how will it distribute? (half of normal saline)
divide into half NS and half pure water
600cc water: 400 intracellular, 150 interstitial, 50 plasma
600cc NS: 450 interstitial, 150 plasma
overall kidney functions?
- maintain homeostasis of fluids and electrolytes
- regulate and produce hormones
kidney filtration: where does it occur? what pressure assists with filtration? what is the filtration barrier?
occurs in glomerulus. hydraulic pressure in glomerular capillary forces fluid into urinary space. basement membrane provides a filtration barrier
qualities of the glomerular basement membrane (GBM)? what particles will get across easily? what is minimally filtered?
charge and size barrier - smaller and + charged particles will move across easily. (electrolytes, glucose, urea are freely filtered). albumin is minimally filtered due to large size and neg charge
in renal physiology, what does it mean that a substance is freely filtered?
means that it crosses freely through the GBM. meaning = filtered THROUGH, not filtered OUT.
GFR is determined by what?
GFR = hydrostatic pressure - oncotic pressure
how is creatinine handled in the kidney?
it can be secreted into the filtrate, but not reabsorbed back into the blood stream
what is the normal GFR?
approx 180L/day
where does reabsorption occur?
prox tubule
reabsorption and secretion occur where?
throughout the rest of the tubule (past prox tubule)
Prox Tubule: what % of filtered substances are reabsorbed here?
-reabsorption of 50-90% of filtered substances
Prox Tubule: how does reab generally occur?
-reab generally coupled to Na+ uptake
Prox Tubule: how does water generally act here?
-water passively follows gradient
Prox Tubule: urine leaving has what tonicity?
-urine leaving the prox tub is isotonic to serum
PT: what % Na is reabsorbed here?
50-65%
PT: what % HCO3- is reabsorbed here?
90%
PT: what % of glucose and AAs are reabsorbed here?
100%
Loop of Henle: what kind of transporter works here? what blocks it?
Na/K/2Cl COtransporter.
blocked by loop diuretics
LoH: water permeability?
descending portion is water permeable
ascending is water impermeable
LoH: tonicity pattern?
tonicity increases as you move deeper into medulla. concentrates urine: makes it hypertonic
DT: what kind of transporter? blocked by what?
Na/Cl CO transporter
blocked by thiazide diuretics
DT: what happens to tonicity of urine? why?
becomes relatively dilute as NaCl is reabsorbed
DT: major site of reabsorption of what cation?
Ca2+
CD: what type of channel? blocked by what?
Na+ channel (aldosterone dependent)
blocked by K+ sparing diuretics
CD: what type of water resorption here?
ADH-dependent water reabsorption via aquaporins
CD: main site for regulating what cation?
K+
CD: main site for excreting what? what kind of cells are key to this?
excretion of acid (H+). intercalated cells.
describe the countercurrent mechanism
descending limb of LoH is water permeable. urine becomes concentrated as it descends into medulla. ascending limb is water impermeable. NaCl is reabsorbed here, maintaining high osmolality.
what 3 hormones are produced by the kidney?
renin, erythropoietin, calcitriol
what 6 hormones act on the kidney?
aldosterone, ANP, AtII, ADH, PTH, calcitriol
what ion is the primary determinant of intravascular volume?
Na+
what will stimulate renin production by the kidney?
slow tubular flow rate, low pressure.
renin –> angiotensin –> aldosterone
what stimulates Na reabsorption?
aldosterone
is Na reabsorption stimulated by hyponatremia?
NO
what is the major regulator of K+ secretion?
aldosterone. stimulates Na reuptake, K secretion, and H secretion
how do tubular flow rates affect K+ secretion?
high flow rates maintain a gradient for K+ secretion
how can the composition of the urine affect K secretion?
K follows its electrochemical gradient; negative charges in urine will enhance K secr.
what is the primary regulator of H+ secretion?
pH sensors, aldosterone, H/K channels
what effect does aldosterone have on H secr?
stimulates H+ secretion
what effect does Angiotensin II have on bicarb reabsorption?
stimulates bicarb reabsorption
H+ secr varies inversely with what levels?
K+
what quality of the renal medulla makes it possible to reabsorb water?
the high osmolality of the renal medulla
what quality of the distal tubule makes it possible to excrete water (ie, to dilute urine)?
NaCl reabsorption in the water-impermeable distal tubule
what is the range for urine osmolality?
50-1200 mosm/Kg
what regulates the amt of water reabsorption/secretion?
ADH
what stimulates the release of ADH?
osmoreceptors, which detect a rise in plasma osmolality and stimulate ADH release to increase water reabsorption
normally, what will shut down ADH secretion?
low plasma osmolality (ie, dilute plasma)
what will low plasma Na+ do? what will it NOT do?
low plasma Na+ will decrease water reabsorption, but it will NOT stimulate Na reabsorption
what fraction of water remains in the vascular space (plasma)?
1/12
how good of a blood volume expander is water?
not great, but better than nothing
what can override osmolar control to stimulate ADH release?
Hypovolemia can override osmolar control and stimulate ADH release irrespective of plasma osmolality.
generally, what does disease of the med to large vessels tend to do to the kidney? (ie, renal artery stenosis, atherosclerosis, occlusion of branch arteries)
tends to limit blood flow to the glomerulus
what happens when blood flow to the glomerulus is limited (perhaps by vascular disease)?
renal blood flow decreases but the filtration barrier and tubular function remain intact
how does the JGA respond to a drop in renal blood flow?
JGA will produce renin when JG cells are NOT stretched by blood volume
what is a mechanism to maintain/preserve GFR in the setting of hypertension?
efferent arteriolar constriction??
what occurs in the late stages of vascular disease?
GFR falls despite efferent arteriolar constriction. substances that are normally filtered through will accumulate.
define tubulointerstitial disease? what can it lead to?
alterations of tubular function that leads to wasting or retention of substances: glycosuria, renal tubular acidosis, potassium disorders, diabetes insipidus.
tubular obstruction or necrosis can lead to what?
can decrease GFR by back pressure, or possibly by feedback mechanisms
how can infection manifest in the kidneys? how will noninfectious inflammation present?
bacteriuria (bacteria in the urine) or pyuria (white blood cells in the urine).
noninfectious inflammation will present as sterily pyuria
glomerular disease will manifest how?
as alteration in the filtration barrier: either proteinuria or hematuria. may also affect GFR.
what is glomerulonephritis? what are examples?
inflammation of the glomerulus. ex: Goodpasture’s, membranoproliferative glomerulonephritis (MPGN)
what is the principal manifestation of glomerulonephritis? what is pathognomonic sign?
hematuria.
RBCs are often dysmorphic.
RBC casts are pathognomonic for glomerulonephritis.
what is the sine qua non of nephrotic syndrome? what else may be present?
proteinuria.
may also have edema, low serum albumin, hyperlipidemia, lipiduria
what do we need for dx of nephrotic syndrome? (3 items)
- proteinuria (>3g/d)
- hypoalbuminemia (<3g/dL)
- edema
if a patient has lost 1L of blood volume, we’d have to use how much NS to replace it?
4L (only 1/4 or NS remains in vascular space - since there is Na it will all stay extracellular)
urea concentration in plasma compares how to urea concentration in Bowman’s capsule?
same: urea filters freely
what is a key biomarker for glomerular filtration?
creatinine
if glucose is found in the urine, what should we conclude?
almost always a disease state
how does the prox tubule accomplish the job of reabsorbtion?
couples reabsorbtion to Na uptake, which causes a chemical gradient.
how do thiazide diuretics work? what is a side effect of thiazide diuretics?
block Na/Cl cotransporter in early DT. hypercalcemia
where are the Principal cells located?
collecting duct
what will cause the body to get rid of excess sodium?
hypervolemia. hypernatremia will not cause this response.
mild hypovolemia will induce what response? what about more severe hypovolemia?
mild: activates aldosterone. more severe: activates ADH.
2 things that activate aldosterone
Hyperkalemia
Angiotensin II
3 functions of aldosterone
H secretion
K secretion
Na uptake (via ENaC)
A/B - in event of alkalosis, what happens to K balance? acidosis?
alkalosis: hypokalemia - the H gets reabsorbed from the lumen and removes K (via H/K transporter)
acidosis: hyperkalemia
