Term
|
Definition
| water comprises 50-70% of total body weight |
|
|
Term
|
Definition
total body weight - fat content of body
73% water and 27% solids |
|
|
Term
| distribution of water between body fluid compartments |
|
Definition
intracellular fluid - 40%
extracellular fluid - 20% (interstitial fluid - 15% and plasma = 5%) |
|
|
Term
| T/F water moves from low to high osmolarity |
|
Definition
|
|
Term
|
Definition
caused by loss of water
loss of water from ECF = increased ECF osmolarity and produces a shift of water from ICF to re-establish steady state.
result: proportional decrease in volume of both ECF and ICF and increase in osmolarity |
|
|
Term
|
Definition
due to pathology/loss of Na+
loss of Na+ decreases osmolarity of ECF and causes water to shift to ICF. Since ICF volume increases and ECF volume decreases, hematocrit increases |
|
|
Term
|
Definition
loss of ECF
no change in ICF volume or in overall osmolarity.
No change in volume of erythrocytes in ICF, in ECF (since volume decreases) the erythrocytes now occupy a greater fraction of blood volume |
|
|
Term
|
Definition
infusion of isotonic NaCl adds NaCl and water to ECF, but doesn't change its osmolarity.
no fluid shift, ECF and TBW increase and ICF stays the same |
|
|
Term
|
Definition
ingestion of dry NaCl
adds osmoles to ECF, so fluid shifts from ICF to ECF
new steady state: total OSM and ECF volume increased, ICF volume decreased |
|
|
Term
|
Definition
drinking water and SIADH
lower ECF OSM, so fluid moves from ECF to ICF
new steady state: total OSM decreased and ECF/ICF volumes increased |
|
|
Term
| 2 processes that allow for volume regulation by the kidney to occur |
|
Definition
1. formation of ultrafiltrate of plasma of 180 L/day
2. modification of this ultrafiltrate by subsequent reabsorption and secretion to produce the final urine between 1-1.5 L/day |
|
|
Term
| measurement of renal clearance |
|
Definition
Cx = UxV/Px
Cx = clearance of any substance
Ux = urinary [] of substance x
V = urine flow rate (volume/unit time)
Px = plasma [] of the substance |
|
|
Term
|
Definition
clearance ratio = Cx/Cinsulin
Cx = clearance rate
Cinsulin = clearance of insulin
ratio 1:1 = x is like insulin, neither secreted nor absorbed
ratio 1:>1 = x is filtered and secreted by the kidney
ratio 1:<1 = x is filtered and reabsorbed by the kidney |
|
|
Term
| how much of the cardiac output does the kidney receive? |
|
Definition
|
|
Term
|
Definition
the regulation of renal blood flow over a wide range of BPs (80-180 mm Hg) by changing the resistance of the afferent arterioles
ensures that the glomerular filtration rate is maintained constant over a wide range of arterial pressures |
|
|
Term
| myogenic autoregulation hypothesis |
|
Definition
| afferent arterioles streached by an increase in BP undergo contraction, resulting in an increase in resistance that prevents any increase in blood flow or GFR |
|
|
Term
| tubuloglomerular feedback |
|
Definition
| increases in GFR resulting from an increase in renal blood flow increases delivery of solute in the nephron. This is sensed by the macula densa which increases the resistance of the afferent arterioles and restore GFR |
|
|
Term
| true renal plasma flow (RPF) |
|
Definition
| RPF = [U]pah x V/[RA]pah - [RV]pah |
|
|
Term
|
Definition
GFR = Kf x net ultrafiltrate pressure
Kf = glomerular filtration coefficient |
|
|
Term
| net ultrafiltration pressure |
|
Definition
NUP = Pgc - Pbs - PIgc
net ultrafiltration pressure = given by glomerular capillary hydrostatic pressure minus the opposing hydrostatic in the urinary space of Bowmans capsule minus the capillary oncotic pressure |
|
|
Term
|
Definition
filtration fraction = GFR/RPF
usually approximately 20% (20% of renal plasma flow is filtered across the glomerular capillaries |
|
|
Term
|
Definition
transport of a substance from the glomerular filtrate in the lumen of the nephron to the peritubular capillary blood
water, Na+, Cl-, HCO3, glucose, amino acids, Ca2+, and phosphate |
|
|
Term
|
Definition
transport of a substance from the peritubular capillary blood to the tubular fluid. Fewer substances are secreted than reabsorbed
organic acids and bases, H+ and K+ |
|
|
Term
| resorption or secretion rate |
|
Definition
resorption of secretion rate = filtered load - excretion rate
if filtered load > excretion rate, there has been net reabsorption
if the filtered load < excretion rate, then there has been net secretion |
|
|
Term
|
Definition
| filtered load = GFR x plasma [] of the substance of interest |
|
|
Term
| glomerular hydrostatic pressure (Pgc) |
|
Definition
| depends on arterial pressure and the resistance of the afferent and efferent arterioles |
|
|
Term
|
Definition
| raised levels of plasma glucose increase filtered load so that it exceeds the reabsorptive capacity of the nephron |
|
|
Term
|
Definition
| increase in GFR increases the filtered load of glucose |
|
|
Term
|
Definition
| results from a decrease in Tmg due to a decline in the number or affinity of the Na+ glucose transporters |
|
|
Term
|
Definition
occurs in the proximal tubule in two steps
Na+ cotransport (secondary active transport) takes place on the luminal membrane
facilitated diffusion on the basolateral membrane |
|
|
Term
|
Definition
the sum of the filtration and secretion
increases steeply at low plasma [] and then less steeply once secretion is saturated |
|
|
Term
| at what plasma level does glucose start to appear in the urine? |
|
Definition
|
|
Term
| tubular transport maximum for glucose |
|
Definition
| at threshold when the reabsorption of glucose reaches its maximum |
|
|
Term
| Na+-glucose co-transporter |
|
Definition
located in the luminal membrane of the early proximal tubule
glucosuria occurs when this pump becomes saturated |
|
|
Term
|
Definition
| when the glucose threshold is reached at a lower plasma glucose [] than the Tmg |
|
|
Term
| PAH (para-aminohippuric acid) |
|
Definition
member of a heterogeneous group of compounds that is secreted by active anion transport into the proximal tubule
it is almost completely removed from the plasma in a single passage of blood thru the kidney |
|
|
Term
|
Definition
low pH = uncharged HA predominates
high pH = A- predominates |
|
|
Term
|
Definition
low pH = BH+ predominates
high pH = uncharged B predominates |
|
|
Term
| T/F only the charged form of weak acids and bases can diffuse from the blood into the urine |
|
Definition
| false, only uncharged form |
|
|
Term
|
Definition
| kidneys secrete ammonia in order to eliminate acid in the urine |
|
|
Term
|
Definition
continuously produced in the body and excreted by the kidneys (10%)
both reabsorption and secretion occur in the proximal tubule |
|
|
Term
|
Definition
used for gout, inhibits uric acid reabsorption
causes elevated urine levels and risk of crystal formation in the kidney |
|
|
Term
|
Definition
major nitrogen containing waste product of the body and is excreted in urine
contributes to the formation of concentrated urine |
|
|
Term
|
Definition
a passive process that requires:
a concentration gradient
a freely permeable tubular epithelium |
|
|
Term
| how much urea is excreted in the urine? |
|
Definition
|
|
Term
|
Definition
proximal tubule - as water is reabsorbed, this increases the urea [] and causes it to be reabsorbed as well
thin descending limb of henle - urea moves down it's [] gradient into the tubule
thick ascending limb, distal tubule, and medullary collecting ducts - impermeable to urea, but water is reabsorbed
inner medullary collecting duct - reabsorbs the high [] of urea now in the tubule after water reabsorption |
|
|
Term
| T/F high urine flow rates promote urea excretion |
|
Definition
|
|
Term
| what constitutes the major ECF solute? |
|
Definition
| Na+ is the major cation and Cl-/HCO3 are the major anions |
|
|
Term
| what is the most important function of the kidney? |
|
Definition
| regulation of Na+ balance |
|
|
Term
| what 2 processes are involved in the movement of Na+ ions from the tubular lumen back into the blood? |
|
Definition
1. on the luminal membrane, Na+ enters the cell down its electrochemical gradient via a co-transport mechanism
2. on the basolateral cell membrane, Na+ is extruded by the Na+/K+ ATPase |
|
|
Term
| features of the early proximal tubule |
|
Definition
Na+ co-transport in the luminal membrane of the epithelial cell
Na+-H exhange in the luminal membrane
preferential reabsorption of HCO3 over Cl-
isosmotic reabsorption of fluids |
|
|
Term
|
Definition
| retrieve valuable classes of molecules from the urinary filtrate including glucose, AAs, phosphate, sulfate, mono-, di- and tri-carboxylic acids |
|
|
Term
|
Definition
| so thorough that only traces of amino acids appear in the urine of healthy people |
|
|
Term
|
Definition
| occurs primarily in the proximal tubule (80%), another 10% in the distal tubule, and 10% is excreted |
|
|
Term
| features of the late proximal tubule |
|
Definition
high luminal Cl- []
Cl- reabsorption and diffusion between cells
isosmotic reabsorption |
|
|
Term
|
Definition
1. Na+ entry across the luminal membrane occurs down electrochemical gradient - co-transport
2. active transport of Na+ occurs across the basolateral membrane - Na+/K+ ATPase
3. driving force for water reabsorption is created due to removal of Na+
4. water moves to intercellular spaces by osmosis
5. isosmotic fluid in intercellular spaces is reabsorbed because of an increase in capillary oncotic pressure |
|
|
Term
| thick ascending limb of loop of Henle |
|
Definition
reabsorbs 25% of the filtered Na+ without water (always impermeable)
Na+ [] and osmolarity decreases and interstitial fluid becomes hyperosmotic
Na+-K+-2Cl- co-transporter in the luminal membrane |
|
|
Term
|
Definition
| thick ascending limb of loop of Henle |
|
|
Term
| early distal tubule features |
|
Definition
reabsorbs about 5% of Na+ and is impermeable to water
Na+-Cl- co-transporter in luminal membrane
on basolateral side, Na+ leaves via Na+/K+ ATPase and Cl- via a channel |
|
|
Term
|
Definition
reabsorbs about 3% of Na+
site of action for aldosterone and ADH
contains principal cells and intercalated cells |
|
|
Term
| cortical diluting segment |
|
Definition
|
|
Term
| principal cells of distal tubule |
|
Definition
Na+ reabsorption is fine tuned
Na+ channels in the luminal membrane (aldosterone)
secretion of K+
water reabsorption is variable (ADH) |
|
|
Term
|
Definition
| stimulates Na+ reabsorption in the kidney |
|
|
Term
|
Definition
| stimulates Na+ reabsorption in the proximal tubule |
|
|
Term
| what is the most abundant intracellular cation in the body? |
|
Definition
|
|
Term
| what is the physiological range of extracellular K+ []? |
|
Definition
|
|
Term
|
Definition
redistribution between ECF and ICF
shifts K+ across cell membranes normally occur to maintain the K+ [] in ECF in normal range |
|
|
Term
|
Definition
dietary intake, rental excretion and GI secretion
matching daily excretion of K+ with ingestion |
|
|
Term
|
Definition
decrease in ECF or plasma K+ []
causes:
insulin
aldosterone
EPI
metabolic alkalosis
NaHCO3
hypo-osmality of ECF |
|
|
Term
|
Definition
loss of K+ from cells and increase ECF or blood K+ []
causes:
lack of insulin
aldosterone insufficiency
metabolic acidosis
hyperosmolarity of ECF
damage to cells
loss of function of Na+/K+ ATPase |
|
|
Term
| K+ reabsorption in the proximal tubule |
|
Definition
roughly proportional to Na+ and water reabsorption
mostly passive process via solvent drag between lateral intercellular spaces |
|
|
Term
| thick ascending limb of loop of Henle |
|
Definition
K+ is moved into the cell on luminal side by Na+-K+-2Cl- co-transport
K+ moves passively thru paracellular path anc across basolateral membrane thru K+ channels
water impermeable (no solvent drag) |
|
|
Term
| K+ reabsorption in distal tubule and collecting duct |
|
Definition
K+ usually secreted into the tubular fluid
alpha-intercalated cells and principal cells present |
|
|
Term
| alpha-intercalated cells of distal tubule |
|
Definition
| reabsorb K+ when K+ intake is low (H+-K+ ATPase) |
|
|
Term
| what 4 factors determine the rate at which K+ is secreted |
|
Definition
| dietary intake, the action of aldosterone, acid/base balance, and tubular flow rate |
|
|
Term
| influence of diet on K+ secretion |
|
Definition
high K+ intake increases uptake of K+ by Na+/K+ ATPase, which increases intracellular [] as well as the driving force for K+ secretion
high K+ in plasma stimulates aldosterone secretion and therefore K+ uptake and secretion
decrease in K+ intake decreases secretion |
|
|
Term
| influence of aldosterone on K+ secretion |
|
Definition
| aldosterone is increased by an increase in plasma K+ and it then stimulates Na+/K+ ATPase to increase intracellular K+[] and therefore K+ secretion |
|
|
Term
| influence of acid/base balance on K+ secretion |
|
Definition
alkalosis - increase uptake of K+ by cells and release of H+ into ECF (hypokalemia) and increases K+ secretion
acidosis - H+ is taken up by cells, and K+ released into ECF (hyperkalemia) and decreases K+ secretion |
|
|
Term
| influence of urinary flow rate on K+ secretion |
|
Definition
| increases in flow rate dilute the K+ [] in the lumen - increase in magnitude of K+ gradient and increase in K+ secretion |
|
|
Term
|
Definition
diuretics
metabolic alkalosis
excess corticosteriods
GI losses
renal disease |
|
|
Term
|
Definition
muscle weakness
loss of motility
abnormalities in myocardial contraction
changes in EKG |
|
|
Term
|
Definition
acute renal failure
renal disease
acidosis
tissue breakdown/damage
adrenal insufficiency
poor renal perfusion |
|
|
Term
|
Definition
hyperexcitable muscles
slows cardiac conduction of APs
ventricular fibrillation |
|
|
Term
| T/F both alcohol and caffeine stimulate ADH secretion |
|
Definition
| false, they both inhibit it |
|
|
Term
| cortico-medullary osmotic gradient |
|
Definition
(the role of the loop of Henle) an osmotic gradient from the renal cortex to the innermost papilla
necessary for producing concentrated urine |
|
|
Term
| what are the 3 components involved in forming hyperosmotic urine? |
|
Definition
1. formation of corticopapillary gradient by the loops of Henle (countercurrent multiplication)
2. vasa recta (blood vessels that help maintain the gradient)
3. ADH, which makes cells of distal tubule/collecting duct permeable to water |
|
|
Term
| what process renders the medullary and papillary interstitial fluid hyperosmotic? |
|
Definition
| the reabsorption of NaCl without water |
|
|
Term
| steps of countercurrent multiplication in the loop of Henle |
|
Definition
step 1: loop is filled with fluid from proximal tubule that is osmotic with plasma (300 mOsm/L)
step 2: NaCl is reabsorbed via Na+-K+-2Cl- co-transport in thick ascending limb (water impermeable, so this dilutes the luminal fluid and makes it hypo-osmotic, while the interstitial fluid becomes hyperosmotic) - water then leaves is descending loop to become isosmotic
step 3: process continues as fluid is moved through the nephron |
|
|
Term
|
Definition
| when solute transport is separated from water transport |
|
|
Term
| countercurrent exchange in the vasa recta |
|
Definition
as blood flows thru the medulla with increasing interstitial osmolarity, solute diffuses into the blood and water diffuses out (blood osmolarity increases as it moves deeper into the medulla)
when blood returns toward the cortex, it runs into decreasing osmolarity and solutes diffuse out as water moves in |
|
|
Term
|
Definition
target cells = principal cells of distal tubule/collecting duct
causes a series of events that allow for incorporation of aquaporins within the luminal membrane of these cells |
|
|
Term
| what occurs during water diuresis? |
|
Definition
1. ADH is very low or absent
2. osmolarity of medulla is about 1/2 of the concentrating kidney (decreased activity of Na+-K+-2Cl- co-transporter, and lack of water reabsorption in late distal tubule) |
|
|
Term
|
Definition
|
|
Term
|
Definition
CO2
between 13,000 and 20,000 mmoles are produced per day due to oxidative metabolism
CO2 reacts with water to form carbonic acid |
|
|
Term
|
Definition
non-volatile (H2SO3 and H3PO4)
produced by catabolism of proteins and phospholipids at a rate of 50-70 mEq/day
also included are formic acid, ketoacids, lactic acid which arise from oxidation of FAs |
|
|
Term
|
Definition
consist of a weak acid and its conjugate base (or weak base and its conjugate acid)
minimizes but does not prevent the change in pH when an acid or base is added to it |
|
|
Term
| henderson hasselbach equation |
|
Definition
| logarithmic form of the acid dissociation equation |
|
|
Term
|
Definition
shows the pH obtained vs. the amount of strong acid or base added to the solution
the slope of the curve is a measure of the effectiveness of the buffer (the flatter the slope, the less the shift in pH that occurs when a given amount of acid is added) |
|
|
Term
| when is the slope of the titration curve flattest? |
|
Definition
| when the pH equals the pKa of the buffer (so, optimal buffering is obtained near the pKa of the buffer) |
|
|
Term
| what are the physiological buffers? |
|
Definition
ECF = bicarbonate (HCO3) and dihydrogen phosphate (H2PO4)
ICF = hemoglobin and organic phosphates
kidney = ammonia |
|
|
Term
|
Definition
| the relative contribution of a given buffer to overall buffering depends on the value of its pKa, the amount present and its accessibility |
|
|
Term
|
Definition
pKa = 6.8 (close to blood pH)
[] in blood is low, so buffering capacity is limited |
|
|
Term
|
Definition
provide the largest amount of buffering in the body
deoxyhemoglobin is a better buffer than oxyhemoglobin - conveys H+ to the lung |
|
|
Term
|
Definition
most important ECF buffer
pKa = 6.1
CO2 and bicarbonate are regulated by the lung and kidney |
|
|
Term
| normal values of HCO3-, PCO2, and pH |
|
Definition
pKa = 6.1
HCO3 = 24 mM
CO2 = PCO2 x 0.03
40 mm Hg x 0.03
1.2 mM
pH = 7.4 |
|
|
Term
| role of respiratory system as a buffer |
|
Definition
an decrease in pH will increase the ventilation rate and lower PCO2
an increase in pH will decrease the ventilation rate and cause a rise in PCO2 |
|
|
Term
| 2 major roles of the kidney in acid/base balance |
|
Definition
1. reabsorption of the bicarbonate (proximal tubule)
2. eliminate fized acid from body (distal tubule and collecting duct) |
|
|
Term
| reabsorption of filtered bicarbonate |
|
Definition
results in net reabsorption of both Na+ and HCO3-
doesn't secrete H+, it is simply recycled across the membrane
little or no change in tubular pH
requires presence of carbonic anhydrase |
|
|
Term
| effect of ECF volume on HCO3- reabsorption |
|
Definition
expansion = dilution of plasma protein and decrease in plasma oncotic pressure (reduced fluid and reabsorption)
contraction = increases [] of plasma proteins and plasma oncotic pressure (more fluid and reabsorption) |
|
|
Term
| increased PCO2 (respiratory acidosis) |
|
Definition
| increased PCO2 = increased CO2 in renal cells = increased HCO3- reabsorption = increased blood HCO3- |
|
|
Term
| decreased PCO2 (Respiratory alkalosis) |
|
Definition
| decreased PCO2 = decreased CO2 in renal cells = decreased HCO3- reabsorption = decreased blood HCO3- |
|
|
Term
| excretion of H+ as a titratable acid |
|
Definition
titratable acid is measured by determining the milli-equivalents of strong base needed to bring a urine sample to blood pH (usually H2PO4)
accounts for 40% of total H+ secretion
occurs in intercalated cells of late distal tubule and collecting duct via H+ ATPase |
|
|
Term
| H+ excreted as an ammonium ion (NH4+) |
|
Definition
accounts for about 60% of H+ excretion
takes place in proximal tubule, thick ascending limb, and intercalated cells of collecting duct
secretion of NH4+ is linked to reabsorption of HCO3- |
|
|
Term
|
Definition
| when NH3 diffuses into the lumen of the tubule and combines with H+ to form NH4+, the positively charged NH4+ cannot cross the lipid cell membrane and is trapped in the lumen |
|
|
Term
| 4 simple acid/base disturbances |
|
Definition
| metabolic acidosis, metabolic alkalosis, respiratory acidosis, respiratory alkalosis |
|
|
Term
| causes of metabolic acidosis |
|
Definition
accumulation of lactic acid
loss of bicarbonate
overproduction of acid
renal failure
poisons |
|
|
Term
| causes of metabolic alkalosis |
|
Definition
|
|
Term
| causes of respiratory acidosis |
|
Definition
respiratory depression
airway obstruction
pulmonary disease (mismatch between ventilation and perfusion of alveolae) |
|
|
Term
| causes of respiratory alkalosis |
|
Definition
high altitude
anxiety
deliberate over breathing
stimulation of respiratory centers |
|
|
Term
|
Definition
end stage of chronic kidney disease
defined as kidney damage or decreased kidney GFR of less than 60 mL/min/1.73m for 3 or more months |
|
|
Term
| general features of chronic renal failure |
|
Definition
progressive loss of nephrons
disturbances of fluid balances
disturbances of K+ balance
disorders of Ca2+ and phosphate metabolism
disturbances of acid/base balance
decrease in erythropoietin (anemia) |
|
|
Term
| causes of acute renal failure |
|
Definition
nephrotoxic agents (NSAIDS, ibprofen)
exposure to metals
infections
intravascular hemolysis
trauma |
|
|
Term
|
Definition
a sensation of fullness
input from the cerebral cortex to trigger voluntary urination
input from the micturition center in the pons which coordinates the relaxation of sphincter muscles with the contraction of the bladder |
|
|
Term
|
Definition
| nocturnal incontinence (children) |
|
|
Term
|
Definition
due to cortical damage
common after childbirth or in postmenopausal women, or in men after prostate operations |
|
|
Term
|
Definition
overactive bladder
causes: infections, anxiety, neuro damage that interferes with descending path |
|
|
Term
|
Definition
incomplete bladder emptying
causes: pressure on or obstruction of urethra, sensory disorders, damage to parasympathetic innervation to bladder
common in elderly males with enlarged prostate |
|
|
Term
| automatic bladder incontinence |
|
Definition
occurs with injuries to the spinal cord that separate the descending inhibitory inputs from the pontine micturition center and higher cortical control
voiding is alway incomplete |
|
|
Term
|
Definition
occurs in the absence of any physical abnormality
unable to reach toilet fast enough (common with arthritis and loss of mental faculties) |
|
|
