Renal Physiology Flashcards

Terms Definitions
DISTAL TUBULE
Intercalated Cells
Acid/Base Balance
H/K ATPase
thiazide
diuretic that block Na,Cl cotransporter of distal convoluted tubule
Adenosine
produced in kidneysvasoconstrictor of afferent arterioles, decreasing RBF and GFRmay play a role in tubuloglomerular feedback
AE1
antiporter that releases bicarbonate into blood in alpha intercalated cells
Hydrostatic Oncotic Pressure
•Glomerular capillaries: HIGH hydrostatic P, oncotic P ↑
•Peritubular capillaries: hydrostatic P ↓, HIGH oncotic P
Renal Tubule
Divided into Proximal Convoluted Tubule, Loop of Henle, Distal Convoluted Tubule, and Collecting Duct.
Juxtaglomerular Apparatus
comprised of:
1. macula densa of thick ascending limb; actually a plaque in its walls
2. extraglomerular mesangial cells
3. granular cells of afferent arteriole involved in autoregulation of blood pressure through tubuloglomerular feedback mechanism
Osmolarity
Number of dissociable particles per L of solvent
Esxpressed as milliosmoles/L
(mOsm/L)
What causes high permeability of capillaries in glomerulus?
fenestrations
What is epoetin alfa?
An RBC stimulator.
PROXIMAL TUBULE
- massive reabsorption, volume reduced ~70% but osmolarity of tubular fluid same
•Secretion
-endogenous materials: prostaglandins, bile salts, creatinine
-drugs: penicillin, morphine
-mediated by non-specific cationic & anionic transporters
•Reabsorption
-Sodium: 65%: resorbed via Na/H exchange, cotransport with glucose, AA, H+
-Chloride: 65%: solvent drag following +charge of Na+
-H2O: 65%: simple diffusion (osmosis) by osmotic gradient
-reabsorption of ~65% of filtrate (NaCl& H2O)
-filtrate at beginning & end of PT similar: isotonic reabsorption
-Glucose: cotransport with Na+
-Amino Acids: cotransport with Na+
-100% reabsorption of glucose & amino acids: freely filtered
-Peptides: degraded by brush border peptidases, AA absorbed
-Proteins: endocytosed, degraded
-disappear from filtrate
-Potassium: 80%: solvent drag
-Bicarbonate: 90%: no HCO3- transporters so must use carbonic anhydrase
-CA breaks HCO3- into H2O & CO2 (freely diffuse)
-HCO3- reassembled in cell
-cotransport with Na+ into interstitial space
-transport maximum: limited time & transporters per cell, thus there is a maximum capacity for transport-
-imp example: if huge increase in plasma glucose, not enough time & transport → glucose in pee
Na balance
regulated by neural, hormonal, and hemodynamic factors with short term effects to maintain MBP and long term effects for Na excretion
what factors shift K+ into cells?
EpinephrineInsulinAldosteroneECF alkalosis
Nephron
Functional unit of the Kidney. Fixed, irreplacable number set at birth, typically 800,000 to 1,200,000 per Kidney. Composed of the renal corpuscle and the renal tubule. Two types of nephrons, cortical and juxtamedullary.
Kidneys regulate
composition of body fluid
volume of body fluid
Secondary Active Transport
= indirect active transportrequires ionic gradient energy
urea reabsorption
50% normally passively reabsorbed in PCT
 
all other segments are usually impermeable. under influence of ADH, inner medullary CD's become permeable to urea, which helps establish a strong osmotic gradient to further drive reabsorption of water!!
Starling forces
control distribution of fluid between plasma and interstitium
Does net reabsorption or secretion of water occur in the ascending limb?
No.
What is the normal Ph of Urine?
6.0
Efferent arteriole dilation
↓ glomerular pressure, ↑ peritubular pressure, ↑ RPF, ↓ GFR
the most abundant buffers in body cells and blood; Hb inside RBC is a good buffer
proteins
Henderson-Hasselbalch equation
uses logs and gives pH and pH=pKa+log[HCO3-]/[CO2]; or pH=pKa+log[HCO3]/[0.03*PCO2]; with the pKa is the 6.1 and ratio of HCO3-/CO2 is usually 20:1 (24mM:1.2mM)
what factors stimulate ADH release?
Increased plasma osmalalityDecreased effective circulating volumeThirstStressPregnancy, vomiting
Efferent Arteriole
Carries filtered blood away from the Glomerulus.
Osmosis
movement of water from high conc to low conc through pores in membrane with some displacement of lipidsdriven by osmoic pressure gradient (solute concentration)
Prostanglandins
(may not regulate RBF or GFR in healthy individuals)In hemorrhage (decrease in effective circulating volume), PGI2 and PGE2 are produced within kidneys.They dampen the vasoconstrictor effects of sympathetic nerves and angiotensin II, increasing RBF with no change in GFRThis prevents severe and potentially harmful vasoconstriction and renal ischemia.
intracellular BW makes up how much of body weight?
2/3
renal blood flow
= RPF/ (1-hematocrit), determines how much blood enters the kidney per minute
what do baroreceptors in the carotid sinus detect?
arterial pressure
What is a good measure of the glomerular filtration rate?
Creatinine
sympathetic fibers cause vasoconstriction of afferent arterioles
w/ extreme sympathetic stimulation (exercise or hemorrhage) vasoconstriction of afferent arterioles reduces GFR (lowers urine output and permits blood flow to other tissues)
renal columns (of Bertin)
cortical material that lies between adjacent pyramids where major divisions of blood vessels lie
synthesis of new bicarbonate
fixed acid destroys about 70mEq/day and CO2 is blown off and kidneys must synthesize 70 mEq/day; occurs when proximal tubule secretes NH4+ that is excreted and distal nephron secretes H+ which binds to titratable acids; so when H+ ion is excreted in urine than the HCO3 generated is "new" bicarb
paracellular route of NaCl movement
movement through tight junctions occuring in late proximal tubule; because in first part of proximal tubule HCO3 is rapidly reabsorbed and Cl remains behind causing an increase in Cl conc to 120mM that causes a gradient from tubular fluid to the ISF and Cl diffuses through the tight junctions and Na follows the Cl because of electroneutrality
peritubular capillary network
happens when parent renal corpuscle is not near the cortico-medullary junction representing an arterial protal system
if the macula densa cells detect high levels of sodium, what do they secrete?
Adenosine>>>afferent arteriole>>>constriction>>>lower GFR
Excretion rate
= amount of a substance excreted per unit timenet result of filtration, reabsorption and secretionexcretion rate = V x [U]x(reabsorption/secretion rate = filtered load – excretion rate)
renal vasoconstrictors
work to decrease RBF, ex: Ang II, epinephrine, norepinephrine, thromboxane A2, adenosine
what part of the loop of henle is permeable to water?
descending
functional properties of ENaC
1) high Na specificit2) functional dependence on aldo for channel activation3) specific expression in DCT, CCD, and a bit in the MCD4) inhibition by amiloride
Conditions that increase plasma anion gap
Lactic acidosis, ketoacidosis, ingestion of salicylate
H, drugs
most secretion of __ ions and __ residues
control of acid-base balance
status can be determined by the bicarbonate/CO2 buffer system where [H]=24*PCO2/[HCO3]
How does alosterone affect nephron activity?
Increases activity in principal cellIncrease Na/K atpase and ENaC channels and increase K conductance decreased Na and water excretion
2 substances that can estimate GFR by their plasma clearance levels
inulin and creatinine
reabsorbance and secretion rates:
if the filtered load is > excretion rate, then net reabsorption has occured
if  FL < excretion rate, then net secretion of the substance has occured
filtered load = GFR x [plasma]

excretion rate = [urine] x V

reabsorption = FL - ER

secretion = ER - FL
what factor is GFR dependent on?
net filtration pressure (glomerular surface area and permeability remain constant)
What does ADH do?
it promotes water reabsorption in the DCT/CD
What is the importance of calcium?
bones, teeth, cardiac function, muscle activity
How is potassium balance in chronic alkalosis?
Negative (potassium is excreted)
potent vasoconstrictor that narrows both afferent and efferent arterioles
hormonal reg of GFR* angiotensin II
parietal layer of the Bowman's capsule
simple squamous epithelium and is contunuity with the next portion of the nephron, the proximal convuluted tubule
location of glucose reabsorption
only occurs in the proximal tubule and only can absorb a certain amount per minute
what does too much water rention cause?
Hyponatremia (cells swell and burst)brain swelling
reabsorption in proximal convoluted tubule
filtered glucose and AAs almost 100%, filtered Na/water/K at 70%, filtered urea at 50%
when is/isn't autoregulation effective?
It is good to prevent major changes when BP changes in the ABSENCE of alteration in na balance or ECV. If there IS a change in sodium balance or ECV, other mechanisms overcome this.
Describe hydrostatic pressure in peritubular caps?
Low, like other systemic cap beds. This provides optimal situation for peritubular caps to REABSORB filtered hoh
Substances that are reabsorbed using a gradient-time system
Sodium, potassium, chloride and water
where is action of thiazide diuretics? (HCTZ, chlorthalidone, metolazone)
Distal convoluted tubule
(Blocks Na+ and Cl reabsorption)
Also decreased calcium excretion (by augmenting Na/Ca2+ reabs. in prox tubule)
Na reabsorption in the thick ascending limb of loop of Henle
reabsorbs about 20-25% of filtered load of Na; Na enters by a Na,K,2Cl co transporter; cotransporter is electroneutral but K channels on apical surface of membrane and K leaks back into the tubular lumen creating a lumen-positive tranepithelial voltage difference (stimulated by ADH and vasopressin)
Describe the pathway caused by Renin release
Renin (released when low circulation volume)activated Ang II which causes ADH release from hypothalamus and Aldosterone release from adrenal glandleads to... decreased Na and H20 excretion
Renal Plasma Clearance of PAH
Test that measures total blood flow to the Kidneys
what is the effect of loss of isotonic fluid (eg diarrhea)?
ECF volume decreases.
 
because there's no change in osmolarity, no fluid shift occurs. RBCs do not shrink or swell
 
Hct and plasma protein [] increase.
Which segment reabsorbs te least water? How much?
Ascending loop of henle: absorbs ZERO water
Actions of principal cells of the distal tubule and collecting duct
Aldosterone increases Na receptors in the membrane and increases primary transport by Na/K ATPase. Secondary transport of Na and secretion of K.
reabsorption of Na with Cl by transcellular route
occurs in late proximal tubule uses the Na/H exchanger and Cl/formate exchanger to move Na and Cl into the cell and Na pumps move Na into the basolateral spaces and Cl leaves the cell through channels; the formate ion in lumen combines with H to make formic acid which diffuses back into the cell to dissociate into H and formate
glomerular blood flow's impact on COP
when very low, the volume of filtrate is small and COP rises sharply, thus ceasing filtration along remainder of capillary; when high, rise in COP is minimal and filtration is sustained along capillary
what is a side effect of lasix? why?
hypokalemiabecause there is not as much transport of K from the lumen into the tubule cells due to inhibition of the na/k/2cl cotransporter, and too much K is lost in the urine
Most energy-dependant process in the nephron
Active reabsorption of Na by the basal and basolateral Na/K ATPase
Why is albumin such a good plasma protein buffer?
It has 16 Histine bindings sites Histidine is a good buffer because it has a dissociable proton
what is the net effect of this on the fractional reabsorption of NaCL
it effectively DECREASES the fractional reabsorption. But note--in the abselce of salt load or ECV changes, changes in GFR do NOT change the fractional reabsorption.
why do woman have less body water than men?
woman have higher fat content (more water in muscle than fat)
How can you calculate renal plasma flow with PAH?
RPF = clearance of PAH / E of PAHnormally this comes to 600 mL/min
what is the affect of adding pure water to ECF?
Fluid will shift from ECF to ICF => ICF osmolality will decreaseAfter osmotic equilibrium, added water will be distributed between ICF and ECF according to the initial ICF/ECF ratio of 60%/40% => more fluid will end up inside the cell
What is clearance and how is it calculated?
It's the volume of plasma cleared of a substance over time. Clearance = excretion / Px = Ux X V / Px
GBHP-CHP-BCOP
NFP formula
renal blood flow =
RBF=RPF/(1-Hct)
Lasix
diuretic that inhibits Na,K,2Cl cotransporter and prevents reabsorption
Epinephrine
from adrenal medullavasoconstricts in same manner as norepinephrine
Uncontrolled reabsorption occurs where?
Proximal tubules
osmoreceptors
ECF osmolarity monitored by these located in the hypothalamus and changes in osmolarity are accopanied by changes in cell volume producing changes in plasma ADH levels
Dialysis
Process of cleaning blood externally as treatment terminal renal failure. Small molecules and ions such as water, urea, and potassium diffuse into injected solution which is then drained and discarded.
Reabsorption
of water and solutesfrom glomerular filtrate in renal tubules into blood substances pass through:- luminal/apical membrane of tubule cell- basolateral membrane of tubule cell- (ISF)- capillary endothelial cellInorganic solutes: Na, Cl, HCO3, Ca, Mg, P, ureaorganic solutes: aas, citrate, lactateRequires transporters in membranes of renal epithelial cells
Glucocorticoids
therapeutic doses increase GFR and RBF
RENAL TRANSPORT MECHANISMS
1. Passive Diffusiona. diffusion – via conc gradient or electrical gradientb. osmosisc. solvent dragd. facilitated diffusion2. Active Transporta. coupled transportb. endocytosis
erythropoietin
stimulated by hypoxia, produced by renal cortex, stimulates production of erythrocytes and increases oxygen carrying capacity of blood
where does aldosterone act?
cortical collecting tubule
Is the kidney able to regenerate?
Yes.
Factors Controlling GFR
-Autoregulation I: Myogenic Effect: acts on aff. art.; GFR: keep steady
-afferent arteriole responds to stretch
-High P: constricts to dampen effect of ↑bp
-Low P: dilates to allow more blood flow
-Autoregulation II: Tubuloglomerular feedback: Aff art constrict; GFR: decrease
-↑ in GFR = increased tubular flow (means losing vital things)
-increased tubular flow = increased delivery of NaCl to distal tubule
-macula densa senses ↑[NaCl], release vasoconstrictors to constrict aff art
-macula densa: specialized cells in distal tubule, osmo/chemo receptor of filtrate composition, releases paracrine agents that cause vasoconstriction of afferent arteriole
-Renin-Angiotensin-Aldosterone System: Eff art constrict; GFR: decrease
-systemic ↓bp, ↓volume
Liver secretes angiotensinogen
-granular cells release renin
Angiotensin I
-Angiotensin Converting Enzyme (ACE)(from lungs)
Angiotensin II
-potent vasoconstrictor
-granular (juxtaglomerular) cells: modified sm mm cells in afferent arteriole wall, mechanoreceptor to stretch, secrete renin when lack of stretch is detected in aff art wall
-effects of Angiotensin II
-vasoconstriction of:
-systemic
-efferent arteriole: angio II receptors are predominantly on eff art
-stimulates aldosterone release →↑Na+ & H2O retention, eliminate K+ →↑in systemic volume
-↑ADH & thirst
-Sympathetic Nervous System Aff&Eff art constrict; GFR: decrease
-release NorEpi in response to hypovolemia (also trauma, pain, etc)
-constriction of afferent & efferent arterioles
-↓glomerular flow
-stimulates renin release
-Atrial Naturetic Peptide Aff&Eff art dialate; GFR: increase
-released from atrial myoctyes in response to hypervolemia (↑atrial pressure)
-increased renal blood flow
urinary space
space between the visceral and parietal layers of Bowmans capsule
what hormone is most important and regulating K+ levels after a meal?
Insulin
Renal Cortex
Part of Kidney, contains glomeruli, blood vessels and capillaries, and larger number of renal tubules.
Urine Production
normally 1.2 nephrons per kidneyurine volume: 1-2L/day (can vary 5-18L/day)urine conc: 50 mOsm/L - 1200 mOsm/Lpolyuria: >2 L/dayoliguria: anuria: 0-100 mL/day (kidney disease, prostate enlargement, dehydration)
Solvent Drag
substantial amount of solutes get dragged in with water between cells into proximal tubule
afferent dilation
increases hydrostatic P in glomerular capillaries, increases GBF and GFR
In a healthy kidney, the filtration barrier is freely permeable to:
waterionsglucoseAAurea
What is the Tx for hyponatremia?
Replace Na
Efferent arteriole constriction
↑ glomerular pressure, ↓ peritulbuar pressure, ↓ RPF, ↑ GFR, ↑ FF
15 mmHg opposes filtrationpressure from w/in the capsule onto capillaries
Capsular Hydrostatic Pressure
isohydric principle
all the buffer systems in fluid compartment are in equilibrium with the same H concentration and status of other buffer systems can be calculated from bicarbonate and CO2 concentrations
definition of solutes
movement of solutes from blood (peritubular capillaries) to kidney tubules
how do GFR and plasma creatinine relate to each other?
inversely proportional
Collecting Duct
Straight Part of a Renal Tubule. Distal Tubules of several Nephrons join together here.
2. Tubuloglomerular Feedback
reponse to change in NaCl concentraiton of tubular fluidmacula densa of juxtablomerular apparatus senses NaCl conc of tubular fluid, signals afferent arteriole, altering resistance, example:- increased GFR causes increase in NaCl conc in tubular fluid in Henle’s loop- sensed by macula densa, converted into signal- increase in resistance of afferent arteriole- lowered GFR
Coupled Transport
1. Symport – carrier moves 2 solutes in the same direction; one or both molecules pumped by carrier, 0 or one diffuses- Na-glucose- Na-amino acid- Na-phosphate- 1Na-1K-2Cl in thick ascending limb of Henle’s loop2. Antiport – carrier moves 2 solutes in opposite directions- Na-H antiporter in proximal tubule (apical membrane); uphill movement of H out of cell into tubular lumen using Na gradient as energy source (secondary active transport)- Na-K-ATPase – active transporter in basolateral membrane- H-ATPase- H-K-ATPase – last 2 secrete H in collecting ducts- Ca-ATPase – moves Ca from cytoplasm into blood
plasma creatinine concentration
correlates with GFR, doubling signals loss of 25% renal function (filtration)
factors influencing ADH release
cellular dehydration (increase in effective plasma osmolarity), hypovolemia, a decrease in effective arterial blood volume, pain/trauma/emotional stress/etc., ethanol/atrial natriuretic peptide
normal K concentration in the ECK
3.5 - 5
What is the most common cause of chronic end-stage renal failure?
glomerulonephritis
increases loss of water in urine
ANPatrial natriuretic peptide
reabsorption in distal nephron
type A intercalated cells and reabsorbs about 10-15% of filtered HCO3; similar except that H+ secretion into lumen is via ATPase pump which is electrogenic and not coupled to Na transport and exit of HCO3 is via HCO3/Cl- exchange and no carbonic anhydrase on luminal membrane
terms that can express the concentration of solutes
millimolar (mM=mmol/L), millimolal (mmol/KgH2O), milliequivalent (mEq=6x10^20 charges), milliosmole (mOsmol=6x10^20 particles), milliosmolar (mOsmolar=mOsmol/L), milligram/100mL
definition of flitration
movement of water and solutes from blood (glomerular capillaries) to kidney tubules (Bowman's space)
Plasma Urea Concentration
Inability to excrete urea in addition to acidosis (high H+) and elected K+ concentration which may lead to uremic coma and death.
Filtered Load
= amount of a substance filtered into Bowman’s space per unit timefiltered load = GFR x [P]x
constriction/dilation of arterioles
primary effect is to alter hydrostatic P in glomerular capillaries
what is the value of net filtration pressure?
10 mmHg
What is sodium reabsorption coupled to in the proximal tubule?
Cl reabsorption (passively)glucose, AA reabsorptionSecretion of H+ and Bicarbonate
How is creatinine production calculated?
Creatinine production = creatinine excretion = filtered load of creatinine = [Cr]p X GFR. Creatinine is filtered and secreted, not reabsorbed.
the vol of plasma from which a substance is completely removed by the kidney in a given amt of time
clearance definition
alkalemia
plasma pH is greater than 7.4 or H is less than 40nM
what is the affect of SIADH?
water rention, ANP release, hyponatremia from increased Na lost in urine
what is the equation for plasma clearance?
(urine concentration of substance)(urine flow rate)/plasma concentration of substance
reabsorption of Na+ in the TAL
reabsorbes 25% of filtered Na+
 
Na+/K+/2Cl- cotransporter
(Loops!!!)
 
this portion is impermeable to water, so get dilution of urine here = diluting segment
 
has lumen-positive potential difference (from back-diffusion of K+ through luminal channels) This + lumen potential drives paracellular diffusion of Ca2+ and Mg2+
what are mesangial cells?
they contain actin and myosin (for contraction)
Most physiological mediators of laltered resistance affect the diameter (resistance) of the ____ arterioles more than the _____ arterioles because _____
afferent; efferentthe wall of the afferent arterioles is thicker and more reactive to physiological modulators
Transporters in the basolateral membrane of proximal tubule
Na/K ATPase - luminal membrane secondary Na transporters depend on this.
How is potassium balance in chronic acidosis?
Negative (potassium is excreted)
80% interstitial fluid20% blood plasma
interstitial fluid and plasma amounts within ECF
Ca in plasma
much is bound to other solutes and is not free and reported as milligrams total Ca per deciliter (normally 10mg/dL) about 40% bound to plasma proteins another 10% to anions like phosphate; plasma pH affects binding of Ca to plasma proteins and phosphate
excretion of phosphate
binds to Ca and forms complexes if too high it binds too much Ca lowering the free Ca concentration about 80% of filtered load is reabsorbed in proximal tubule by Na dependent cotransporter and remainder excreted in urine where is acts as a urinary buffer
What is the function of mesangial cells?
provide structural support for glomerular capillaries (Important in regulating glomerular volume and pressure), secrete ECM, phagocytotic activity and secretes cytokines
result of adding 5% NaCl saline solution
increase in salt concentration increases ECF volume, increase in osmolarity causes cellular shrinkage, kidneys will correct it with ADH
what do Macula Densa cells detect?
NaCL delivery to the distal tubule
Describe the Na transport capacity of leaky v. tight epithelia (?)
Leaky: high (?)Tight: low (?)
Characteristics of inulin clearance
A constant amount of inulin is cleared regardless of plasma concentration (parallel line to x axis). Inulin clearance is equal to GFR because it's not secreted nor reabsorbed. If GFR increases, clearance increases (line shifts upward), and vice versa.
where in kidney does aldosterone act?
In collecting duct.
Na+ absorption and K secretion
Na reabsorption of collecting tubules and collecting ducts
principal cells reabsorb about 3% of filtered load; location of sodium reabsorption regulation and Na enters through an apical Na channel (electrogenic uses Na electrochemical Na gradient making urine with Na as low as 5mEq/L)
What are sources of acid from the diet?
Meats, grains and dairy products
Autoregulation of RBF and GFR
1. absent at arterial pressure 2. not perfect – RBF and GFR change slightly as arterial b.p. rises3. GFR and RBF can be changed under appropriate conditions by several hormones.2 Mechanisms:1. Myogenic Mechanism2. Tubuloglomerular Feedback
definition of volume of distribution is
the volume of the body fluid compartment
 
 
what factors affect creatinine levels (other than GFR)?
Age and sex influence muscle mass. Old people have lower creatinien level even w/ormal GFRHigh meat inflences creatinine levelWomen have lower creatinine level
What causes the horizontal gradient?
Since on the AL, water is NOT reabsorbed, but Na is actively reabsorbed, dilution occurs in the AL compared to the DL
Effect of sympathetic stimulation in the nephron
↓ GFR, ↑ FF, ↑ peritubular reabsoption
receptors that detect the effective circulating blood volume
measures the amount of sodium within the plasma and these receptors are sensitive to stretch and are located in 1. renal afferent arterioles; 2. artria and pulmonary vessels (volume); 3. carotid sinus and aortic arch (pressure)
result of adding 2.0L of isotonic saline
fluid volume expansion stays in ECF, GFR increases to correct it, kidneys will excrete Na and water
what happens to bicarbonate in the proximl tubule?
PT reabsorbs most of the filtered bicarbonate to preserve normal a/b balance
What is role of angiotensin II?
(Cleaved to active form by ACE in lung)
-Inc intravascular volume + BP
-Efferent constriction
-Release aldosterone
-Release ADH from posterior pituitary
-Increase thirst
how much of body weight is total body water?
2/360-40-2060% total body weight is water40% is ICF20% is ECF
describe urea concentration in LOH interstitium, + and - ADH
adh + : urea high (due to collecting duct mechanisms)ADH - : urea low.
how do u calculate plasma osmolality? Effective plasma osmality?
P osm = 2(plamsa Na) + (glcuose/18) + (BUN/2.8)leave out BUN for effective P osm
What happens to COP along the length of the glomerular cap? Why?
It rises along the length of the cap--because there is filtration along the length of the cap, then COP rises because the colloid particles essnetially becomme more concentrated becase fliud is filtered but they stay in the plasma
What is the bodies responce to increased effective circulating volume?
Increase ANP (decrease renin) increase GFR increase excretion of Na and water
How is the net transport rate for a substance calculated?
Net transport rate = filtered load - excretion rate = (GFR X Px) - (Ux X V)
Renin
proteolytic enzyme
activates renin-angiotensin-aldosterone system
 regulates blood pressure with Na-K balance 
Liddle syndrome
affects ENaC channel
where is renin produced?
Juxtaglomerular cells
Aldosterone
Major Stimulus: Increased Angiotensin II & Plasma K
Nephron Site: TAL, DT/CD
Effect: Increased NaCl & Water Reabsorption
Acute glomerulonephritis is commonly associated with what bacterial infection?
streptococcus
ureter mucosa
consists of transitional epithelium and underlying lamina propria and typically thrown into fold
Renal Corpuscle
Consists of Bowman's Capsule, Glomerulus, Afferent and Efferent Arterioles
PAH Secretion
= para-aminohippuric acid = hippurateused to measure RPFnot produced in bodyunbound PAH is both filtered and secreted (90% of PAH is bound to plasma proteins)Filtered load of PAH increases linearly as unbound concentration of PAH increases.Transporters in basolateral membrane of proximal tubule cells, can become saturated. Excretion increases linearly with increase in plasma PAH only until Tm is reached. Then excretion increases only with subsequent increase in filtration rate as no additional secretion can occur (transporters saturated).
ANP
Major Stimulus: Increased BP & ECV
Nephron Site: CD
Effect: Decreased water & NaCl reabsorption
excess hydration
sensed by cardiovascular stretch receptors and osmoreceptors, which decreases ADH release and less water is reabsorbed; NOTE: reabsorption at PT is not altered
Acetazolamide
Diuretic that acts on PROXIMAL TUBULE. Inhibits carbonic anhydrase, decreases Na/H exchange
Urine buffer systems
H2PO4- (dihydrogen phosphate) (tritratable acid) buffers 33% of secreted H. NH4+ (amonium) (nontritratable acid) buffers the remaining secreted H.
compensations in respiratory alkalosis
immediate defense is buffering-intracellular buffers supply H+ which enters the ECF in exchange for Na and K and H combines with HCO3 reducing its concentration; kidneys excrete HCO3 and ratio of PaCO2/[HCO3] is improved and H returns toward normal; in chronic respiratory alkalosis the pH may be restored almost to normal by the renal compensation
too much renin can cause what problem?
Hypertension
Vasa Recta
Provide capillary networks for tubules located in the medulla. Formed from Efferent Arterioles from Juxtamedullary Glomeruli.
Ineffective Osmole
permeates cell membrane cannot exert osmotic pressure to balance that generated by solutes of ICF
ex. Urea
Urine
= ultrafiltrate of plasma across the glomerular capillaries
proximal tubular fluid
essentially iso-osmotic to plasma, reflects high water permeability, small gradient drives reabsorption of water
Furosemide (Lasix)
Inhibits Na/K/2Cl transporter in loop of henle. Increases K excretion!
Increased Hct leads to:
increased energy, activity, excerciseimproved eating, sleepingimproved cognitive functionimproved sexual function
Afferent arteriole dilation
↑ glomerular pressure, ↑ peritulbuar pressure, ↑ RPF, ↑ GFR
angiotensin II
increases permeability to water in cells of the distal tubule and collecting duct causing higher water reabsorption
free water clearance
Ch2o=V-Cosm and is quantitive measure of how kidneys handle water when positive the urine osmolarity is less than the plasma osmolarity return body osmolarity towards normal values; when negative urine osmolarity is greater than plasma osmolarity and water is being conserved; and when zero urine osmolarity equals plasma osmolarity and kidney not excreting or conserving water
filtration fraction
fraction of plasma flowing through the glomerulus that is filtered into the Bowman's space can be changed by altering components of the Starling equation by changing the relative diameters of afferent and efferent arterioles (normally 20% in normal humans)
what hormones constrict afferent arteriole?
Renin, Epi, Ang II
Renal Medulla
Part of Kidney. Contains no glomeruli and consists of parallel arrangment of renal tubules and small blood vessels.
 
Typically divided into 8 to 18 conically shaped pyramids.
Specific Gravity
Weight of volume of solution divided by the weight of equal volume distilled H2O
specific gravity of human plasma: 1.008-1.010
used to assess the concentrating ability of the kidneys varies in proportion to its osmolality depends on both the number and weight of solute particles
Autoregulation
GFR and RPF (renal plasma flow) are held within very narrow ranges
organic cations secreted by PTs
histamine, cimetidine, cisplatin, norepinephrine, quinine, tetraethylammonium, creatinine
Controlled reabsorption occurs where?
distal tubules & collecting ducts
Increased afferent resistance does what to Pgc, GFR, and RBF
decreases all of them
Hypovolemia is a deficit of what type of fluid?
ECF
important regulator of pH. the most abundant buffers in extracellular fluid
carbonic acid---bicarbonate
Henderson equation
relates H PCO2 and HCO3-; written as H=800*10^-9*[CO2]/[HCO3-]; H=800*10^-9*[0.03*PCO2]/[HCO3-]; or H(nmol)=24*PCO2/[HCO3-]
effect of reduced renal flow
stimulation of afferent arteriole baroreceptors causing release of renin from JGA; and decreased concentration of Na in the luminal fluid at the end of the loop of Henle which stimulates the macula densa which stimulates the release of renin from JGA
what is the difference between a-intercalated and b-intercalated cells in regard to Cl/HCO3 exchangers?
a-intercalated cells: Cl/HCO3 exchanger located on basolateral membrane so HC03- released into bloodb-inercalated: located on apical membrane so HCO3- is secreted in responce to an alkine load setting
Loop of Henle
Consists of a Straight Decending Limb, Hairpin Loop, and a Straight Ascending Limb.
Juxta Medullary Nephron
1. Long loop of Henle
2. Renal Corpuscle in cortico medullary Junction
3. High Filtration Rate
4. Vasa recta
 
More of these = more water retention
colloid osmotic P in capillaries
decrease (ex: following isotonic saline infusion) causes increase in GFR
where does vasopressin act?
outer and inner medullary collecting ducts
Name such a substance(s) that can cause osmotic diuresis
mannitolglucose in diabetics
Characteristics of a Tm system
Carriers become saturated, carriers have high affinity, low back leak. The filtered load is reabsorbed until carriers are saturated - the excess is excreted.
influences the magnitude of fluid movement into or out of plasma perfusing the kidney
Blood Colloid Osmotic Pressure
compensation of respiratory acidosis
immediately is buffering of excess H+ by hemoglobin and other NBB; cannot have respiratory compensation; renal compensation is slow takin 3-5 days to reach max: new HCO3 generated and PaCO2/[HCO3] is improved; H+ is excreted and [H+] is returned to normal
Which part of the nephron has an apical carbonic anahydrase?
Early proximal tubule
Tubular Transport Maximum (Tm)
Upper limit for the amount of substance than can be transported (e.g. reabsorbed) per unit time.
nephrogenic syndrome of inappropriate antidiuresis
caused by increased V2 receptor activity (AQP2)
Describe water/solute reabsorption in the loop of Henle?
Overall, it reabsorbs more solute than water. Thus, this dilutes the filtrate, since reabsorbate is hyperosmolar to plasma and the tubule fluid at the end is hypo-osmolar.
Characteristics of glucose clearance
At normal glucose levels, clearance is zero. Above treshold levels, clearance increases as plasma concentration increases but never reaches GFR as there's always glucose reabsorption.
Blood cell types that can be formed in the lymph node
plasma cells
lymphocytes
55 mmHgBP in the glomerular capillaries
Glomerular Blood Hydrostatic Pressure (GBHP)
importance in maintaining normal Ca concentrations
for cardiac muscle, excitability of skeletal and nerve, and bone
Short-term regulation of effective circulating volume involves changing what?
Arterial Pressure via changes in HR, cardiac contractility, and vascular resistance by the sympathetic nervous system
Criteria for Marker for Measurement of GFR
1. filttered freely across glomerulus into Bowman’s space2. not reabsorbed or secreted3. not metabolized or produced by kidney4. does not alter GFR in any way
fluid flow past MD decreases
JGA releases renin, angiotensin II is produced, and systemic vasoconstriction occurs; filtration and fluid flow past glomerulus ultimately increases
Describe water reabsorption in distal tubule/collecting duct?
Depends on ADH. These segments express aquaporin 2, which is regulated by ADH.ADH present: DT and CD reabsorb waterADH absent: DT and CD reabsorb much less water
What is glomerular disease marked by? Why?
hematuriaproteinuriaNote: GFR can be variableDue to focal disruptions in the glomerular membrane OR due to loss of negative charge on the membrane
Gold standard to measure RPF
PAH clearance because it's some is filtered and the remaining is all secreted.
Ux * V / PxUx= urine concentration mg/mLVolume of urine flow mL/minPx= plasma concentration (mg/mL)
Clearance measurement of "x"
importance of phosphate
for bone, as a buffer in ECF, as a urinary buffer, and chemistry is intertwined with that of Ca
urine in distal convoluted tubules
H+ and ammonium ions are secreted into the urine and inpresence of aldosterone, Na is actively absorbed and K is secreted
What is the affect of chronic acidosis bone?
Increase ostoclastic function to increase Ca2+ release from bone
4. Excretion of Metabolic Products and Foreign Substances
Metabolic wastes (Amino acids to Urea (50% of nitrogen products), Nucleic acid to uric acid, Phosphocreatine to creatine, Metabolites to hormones, hemoglobin end products) 
  Foreign substances: - chemicals in food - drugs - insecticides and herbicides
Elimination rate matches production
Explain how the kidneys act as secretory glands.
Release 2 hormones: erythropoietin and 1,25-dihydroxyvitamin D (influences calcium balance) and 1 enzyme Renin
How can a substance be completely cleared from plasma flowing through the kidney?
it must be filtered AND secreted
Disease state that would result in an increased BP but no increase in GFR
Atherosclerosis because of an increased resistance to flow in the capillary
effect of TAL on osmolarity gradient
reabsorbs abour 20-25% of Na but does not absorb any water making the tubular fluid dilute and interstitial fluid salty also known as the diluting segment
How is bicarb reabsorbed in the early proximal tubule? In the TAL? In the a-intercalated cells?
Proximal tubule: Na/3HCO3- symport and HCO3/Cl- antiport TAL: HCO3/Cl- antiportIntercalated: HCO3/Cl- antiport
after a lot of reasorption of nutrients/salts in the proximal tubule, what happens to urea?
passive reabsorption of urea due to concentration gradient
What happens then in the descending limb wrt Na movement?
1) no transcellular movement of Na out of the lumen, due to lack of Na/K atpase transporters in basolateral membrane2) Na Leakback back into the lumen due to leasky epithelium and fact that Na concentration in interstitium is high and in lumen it is low
What are the two types of immune mechanisms commonly contribute to glomerular injury?
1. Deposition of circulating soluble antigen-antibody complexes, often with complement components.2. Formation of antibodies specific for the anti-glomerular basement membrane.
increases in BP raise the GFR so that fluid flows too rapidly through the renal tube (Na Cl H2O are not reabsorbed)
vasoconstrictors are released from juxtaglomerular apparatus
What causes fluid to leave the lumen (filtration) along its entire length?
The ballance of starling forces across muscle capillaries
The filtered fluid is then returned to circulation via lymphatics
how does Na go back into tubule cells in the ascending limb?
via a Na/K/2C1 tranporter that transports all 3 ions oout of the lumen
Name 1 of the 5 main functions of the Kidneys
Excrete metabolic waste products from the blood into the urine as fast as they are produced to keep waste products from accumulating in the body.
Why does the descending loop of henle not reabsorb Na+?
One reason is that it lascks the Na+/k+ ATPase transporters that transport Na out across the basolateral surface of tubule cells
weak acids have an HA and an A- form
 
the HA form is readily reabsorbed
 
HA form predominates at acidic pH, so don't get excretion of weak acids with acidic urine
 
alkaline urine, HA predominates, get increased excretion
(so alkalinize urine
weak bases have a BH+ and B form
 
B form readily reabsorbed
 
at acidic pH, BH+ form predominant, increased excretion
 
at basic pH, B form predominant, decreased excretion
 
 
Donnan Effect: why is Na held in the capillary?
It is attracted to the anion charge of the plasma protein
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