# Shared Flashcard Set

## Details

Renal physio
renal physio
95
Physiology
04/18/2009

Term
 Molarity
Definition
 Measure of amount of substance dissolved in a solution-measured in moles/liter -(amt/liter)/ (molecular wgt)
Term
 Equivalence
Definition
 -Similar to osmolarity but accounts for dissociative properties -eg: 150mM of NaCl has 150mM of Na+ and 150mM of Cl-
Term
 Osmolarity
Definition
 [solute]*#of dissociative particles
Term
 Calculating mOsm/L
Definition
 (mmol solute*# of dissociative parts)/Liters of solvent
Term
 What percent of total body weight is water? ICF? ECF? PLamsa? Interstitial fluid?
Definition
 TBW=60% ICF=40% ECF=20% IF= 15% Plasma= 5%
Term
 Osmolality
Definition
 =#of particles/ Kg H20 *NOT dependent on temp b/c weight of water doesn't change with temp
Term
 T or F If a membrane is permeable only to wate and two compartments seperated by this membrane initially contain different solute concentrations, when the compartments reach equilibrium the volumes of the compartments will be equal.
Definition
 False. They will end at the same concentration of solute and water, but different volumes.
Term
 Hypertonic
Definition
 Solution that is more concentrated outside of the cell and causes the cell to shrink
Term
 What happens during iso-osmotic rehydration?
Definition
 Increased volume in ECF, but not changes in osmolarity therefore no change occurs in ICF.
Term
 What happens during hyperosmotic rehydration?
Definition
 1. Initially large increase in ECF volume and   osmolarity 2. Leads to water flow from the ICF to ECF 3. Leads to an increase in osmolarity of ICF
Term
 What happens during hypo-osmotic overhydration?
Definition
 1. ECF volume increases --> decrease in ECF osmolarity 2. Water flow TO the ICF --> increase ICF volume
Term
 How do you determine change in osmolarity after fluid loss?
Definition
 1. Find initial total osmolarity TBW(kg)*osmolarity 2. Subtract total excreted osmolarity=kg*osmolarity 3. Divide by change in body water (L)
Term
 What is the major cation in the ECF? ICF?
Definition
 ECF= Na+ ICF= K+
Term
 About how many nephrons are there in 1 kidney?
Definition
 1.2million/ kidney
Term
 What is the renal medulla?
Definition
 Inner portion of the kidney, composed of 8-18 pyramids
Term
 Where does the base of a renal pyramid start?
Definition
 At the cortico-medullary junction
Term
 What is the papilla?
Definition
 *The apex of a renal pyramid *Leads to the minor calyx, then the major calyx, then the pelvis
Term
 What does the pelvis connect to?
Definition
 *Major calyx and ureter/ urinary bladder *Is technically an expanded portion of the ureter
Term
 Desribe the flow of filtrate in a nephron
Definition
 Glomerular capillaries (thru visceral epithelia) -> bowman's space -> Promixal convoluted then straight tubules -> descending loop of Henle ->thin ascending LH -> thick ascending LH -> (macula densa) ->distal convulted tubule -> cortical collecting duct -> medullary collecting duct -> renal pelvis -> OUT
Term
 What are photocytes?
Definition
 *Epithelial cells around the Bowman's capsule *AKA visceral layer
Term
 Vasa recta
Definition
 *Blood vessels that run entire length of loop of Henle *Only found in juxtamedullary nephrons *Allow concentration of urine
Term
 Cortical/Superficial nephrons
Definition
 -Renal corpsule is located in the cortex -Has a short loop of Henle -Lower filtration rates b/c nephrons are smaller -No vasa recta
Term
 Juxta Medullary nephrons
Definition
 *Have vasa recta *Long loops of Henle *Located toward medulla and loops extend into medulla
Term
 What comprises the renal corpsule?
Definition
 Glomerulus Bowman's space (both parietal and visceral layers)
Term
 How is protein filtered by the renal corpsule?
Definition
 *Glomerular capillaries contain fenestre *Capillaries surrounded by basement membrane *Photocytes of Bowman's capsule surround glomerular capillaries/BM and have slits that allow the filtration of water
Term
 How big are the slits in btwn the foot processes of photocytes? IS there any charge associated? What are the implications on molecule movement?
Definition
 *Slits= 40 Angstrom and have a negative charge *Up to 20 A, free filtration *20-42 A, filtration is variable
Term
 Juxtaglomerular Apparatus
Definition
 1. Macula densa: specialized cells that sense changes in [NaCl] 2. Granular (juxtaglomerular) cells: Produce Renin 3. Extraglomerular mesangial cells: SM like cells interspersed in extraglom space
Term
 What are the functions of the kidney??
Definition
 1.Salt/ H2O regulation 2. Vit D regulation via Ca absorption/excretion 3. RBC production via erythropoietin in peritubular capillary endothelial cells 4. BP regulation 5. Excretion of xenobiotics (substances not normally found in the body, usually drugs, etc) 6. Excretion of metabolic waste
Term
 True or false The proximal convuluted tubule lacks a brush border and mitochondria
Definition
 False: the proximal convoluted tubule has a brush border to aid in reabsorption. It also has mitochondria
Term
 How are renal disease and anemia related?
Definition
 In chronic renal disease, there is decreased erythropoietin produced -> fewer RBCs -> anemia
Term
 True or flase: The ascending (thin and thick) loop on Henle has lots of mitochondria
Definition
 False: they have few mitochondria
Term
 What is inulin used for?
Definition
 *Inulin clearance is used as a basis of comparision for clearance of other substances because is not secreted, reabsorbed, metabolized, or synthesized and is freely filtered *Can be used to calculate GFR
Term
 Peritubular Capillaries
Definition
 *Blood vessels that travel alongside nephrons *Allows reabsorption and secretion bwtn blood and lumen of nephron
Term
 What happens renally when there is decreased O2?
Definition
 More erythropoietin is produced -> more RBCs
Term
 Glomerular Filtration Rate
Definition
 *Rate of movement of fluids and solutes from glomerular capillaries into Bowman's space GFR=Kf* (Hydrostatic glomerular capillary Pressure- hydrostatic Bowman's space pressure) - (osmotic pressure of glomerular capillary)
Term
 What forces drive fluid toward the glomerulas? Toward the Bowman's Space?
Definition
 Glomerulas: Bowman's space hydrostatic pressure  and oncotic pressure of glomerulus   Bowman's: GC hydrostatic, Bowman's oncotic
Term
 Which pressure increases along the glomerular capillary network (toward efferent)? Why?
Definition
 The glomerular capillary oncotic pressure increases because [protein] increases due to filtration of water into Bowman's space
Term
 What is the filtration fraction?
Definition
 FF= GFR/RPF RPF= (1-Hematocrit)* RBF
Term
 Where are there sharp decreases in pressure across the arterioles?
Definition
 There are sharp decreases across the afferent and efferent arterioles
Term
 What happens when the afferent arteriole is constricted?
Definition
 Hydrostatic pressure in the glomerular capillaries decreases -> decreased GFR
Term
 What happens when the efferent arteriole is constricted?
Definition
 The hydrostatic pressure in the glomerular capillary increases -> GFR increases
Term
 What does renal autoregulation refer to?
Definition
 *Afferent arteriole resistance is changed to compensate for changes in BP   *Between a renal arterial pressure 80-160, GFR and renal blood flow remain constant
Term
 Tubuloglomerular feedback
Definition
 *Afferent arteriolar resistance is regulated by changes in flow rate in the tubule *Change in arteriolar pressure -> change in glomerular pressure and plasma flow -> change in GFR -> change in Osm and NaCl whiched is sensed by macula densa, which sends signal to afferent arteriole --> changes in preglomerular resistance
Term
 Autoregulation: Myogenic Mechanism
Definition
 *Regulates the tone of the afferent arteriole *Tendency to contract when stretched *Increased arteriolar pressure -> increased afferent arteriolar stretch -> increased contraction -> RBF and GFR are normalized
Term
 In regards to the kidney, what does the law of mass balance indicate?
Definition
 *If a substance is not metabolized or synthesized, *Arterial input= Venous output + urine output
Term
 Clearance
Definition
 *Volume of plasma cleared of a specific substance  per unit time *clearance= (urine[x]*urine flow rate)/Plasma[x]
Term
 What happens when there is a sudden decrease in GFR?
Definition
 *Initial decrease in excretion of creatinine, but it slowly increases back to normal *No initial change in production of creatinine * Increase in plasama [creatinine]
Term
 About how much water, Na, Cl, HCO3-, Glucose are reabsorbed?
Definition
 Between 99.2 and 99.9
Term
 Where is the primary site for glucose/ AA reabsorption?
Definition
 Proximal Tubule
Term
 What is the typical osmolarity of urine?
Definition
 500-800mOsm/kg of H2O
Term
 Name some compounds that are not in urine.
Definition
 Amino acids, protein, blood, ketones, leukocytes, and bilirubin
Term
 What happens when the filtered load surpasses the capacity of a transporter?
Definition
 The excess is excreted.
Term
 Give an example of cotransport and countertransport
Definition
 Na/Glucose transporter = cotransport Na/H = countertransport
Term
 Give examples of secondary active transport
Definition
 *Na+/AA *Na+/H+ *Na+/Ca *Cl/HCO3
Term
 Na+ reabsorption in the proximal tubule
Definition
 *Na/H countertransporter *Carbonic anhydrase on apical membrane converts bicarbonate into water and CO2 *In cell, water and CO2 are converted back to HCO3- by CA
Term
 Na reabsorption in the thick ascending LH
Definition
 *Na-K-Cl symporter drives into cell *Leads to K secretion *Na, Ca, K, and Mg cations can be reabsorped via paracellular transport   **Thick ascending LH is impermeable to water therefore it is called the diluting segment of the nephron
Term
 Describe Na reabsorption in the early distal tubule.
Definition
 *Cotransport of Na/Cl *Impermeable to water
Term
 Reabsorption in the late DCT and collecting ducts
Definition
 -Na via ENaC channels -K/H antiporter (K in, H out) in apical -Carbonic Anhydrase in epithelial cell converts H2CO3 -> HCO3- and H+, HCO3- diffuses to IF, H into lumen   -H2O only reabsorbed if ADH present
Term
 Where is the ENaC channel found? What does it do? What inhibits it?
Definition
 -Late distal tubule/ collecting duct -Diffusion of Na into the cell -Inhibited by ameloride (Potassium sparing diuretic)
Term
 What is TF/P? What does it measure?
Definition
 TF= concentration of substance or osmolarity in the proximal tubule fluid   P= blood plasma concentration   *Relative concentrations *If proximal tubule reabsorbs 1/2 of water, and no inulin, the Tf/P value would double (because it is now twice as concentrated)
Term
 Which aquaporin is regulated by ADH?
Definition
 Only AQP2
Term
 Is the IF or the tubular lumen slightly hypertonic?
Definition
 The IF is slightly/ "effectively" hypertonic because solutes are transported with a high affinity
Term
 What parts of the nephron do not allow water reabsorption?
Definition
 Never: Thin and thick ascending loop of henl, distal convoluted tubule, and cortical tubule    Only when ADH present: Cortical collecting duct and Inner-medullary collecting duct
Term
 What is mannitol used for? How/ where does it work?
Definition
 Works in the proximal tubule by making the lumen/ fluid hypertonic -> less H2O reabsorption/ water remains in tubule -> excretion
Term
 What is diamox used for? Where/How does it work?
Definition
 Diamox is a diuretic used in the proximal tubule. It inihbits the carbanic anhydrase -> eventual inhibition of flux -> more sodium in tubule -> increased excretion
Term
 What are thiazides? Where/how do they work?
Definition
 Thiazides are duiretics that work in the distal convoluted tubule by inhibiting Cl- transport (which is coupled in cotransporter to Na+) *work at TSC1
Term
 What are furosemide/ bumetanide? Where/how do they work?
Definition
 Furosemide and bumetanide work in the thick ascending limb. They compete for with the Cl- on the 2Cl/Na/K cotransporter (BSC1)   These are considered K wasting (b/c potassium is excreted) and are not used on patients with heart conditions.
Term
 Where/ how do ameloride and triamterene work?
Definition
 -Works on the ENaC channel in the collecting duct. -Inhibits Na reabsorption by binding to ENaC -K sparing because it has little affect on K reabsorption
Term
 What is an example of something that is not filtered?Filtered, secreted and excreted? filtered and reabsorbed? Filtered and completely excreted (no reabsorption)?
Definition
 1. Erythrocytes, proteins 2. Penicillin 3. Glucose 4. Creatinine
Term
 What is/are the major determinants of plasma osmolality?
Definition
 Na+ Cl-, HCO3-
Term
 Describe the tubular fluid osmolality along the nephron.
Definition
 *No change in proximal tubule because H2O/Na reabsorbed iso-osmotically *Sharp increase in TF/P in the descending loop of Henle then sharp decrease in the ascending *Past here it depends on conditions of diuresis or antidiuresis  Antiduiresis: Osmolality increases a lot as water is   reabsorbed and solute is not  Diuresis: Osmolality decreases as some solute is    reabsorbed and water is not
Term
 What is antidiuresis? Diuresis?
Definition
 Anti: State of water conservation because of water restriction   Diuresis: Excess water -> excretion
Term
 Is a lot or little water excreted when AVP is low?
Definition
 Lots
Term
 What stimulates ADH release from posterior pit?
Definition
 Plasma osmolality and volume contraction
Term
 What is the relationship between ADH levels, urine osmolality and total solute excreted?
Definition
 Increased ADH -> less water excreted -> increased urine osmolality   *Total solute excreted is constant, osmolality changes because of changing water amounts
Term
 How much change in blood volume or pressure is necessary to regulate ADH secretion?
Definition
 5-10%
Term
 How does change in vol/pressure --> changes in ADH secretion?
Definition
 Baroreceptors on coratid sinus, aortic arch, left atrium, and pulmonary vessels detect Vol/P change --> Stimulation of afferent vagus and glossopharnygeal nerves --> Input relayed to supraoptic and paraventricular nuclei --> Secretion of ADH
Term
 Mechanism for ADH action in collecting ducts
Definition
 AVP binds V2 receptor -> cAMP -> PKA -> AQP2 insertion in apical membrane of epithelial cells
Term
 Mechanism of water diuresis
Definition
 1. Fluid leaving proximal tubule is iso-osmotic 2. Water is passively reabsorbed in the thin descending loop, no solute reabsorption 3. NaCl absorption in thin/thick ascending but no water 4. Distal tubule and collecting ducts impermeable to water w/o ADH therefore 5. Medullary CD actively absorbs NaCl
Term
 What is Diabetes Insipidus?
Definition
 Central: caused by trauma or pituitary surgery; decreased ADH production -> polyuria   Nephrogenic: Caused by mutations in V2 receptor or AQP2 gene; results in ADH resistance -> Polyuria
Term
 True or false: When sodium intake is increased it leads to an increase in body weight because of a delay between intake and increased excretion
Definition
 True: There is a positive sodium balance for a few days
Term
 Describe the basic feedback mechanisms for control of blood volume/ ECF
Definition
 ΔIn blood Vol -> Δ in CO -> Δ in arterial pressure -> Δ in urinary output -> Δ in ECF vol -> Δ in blood vol
Term
 ECF sensors
Definition
 1. Vascular     a. low pressure: cardiac atria & pulmonary vasc     b. High pressure: carotid sinus, aortic arch,        juxtaglomerular apparatus 2. CNS 3. Hepatic
Term
 Intrarenal mechanisms for control of Na excretion
Definition
 *Autoregulation of renal plasma flow *Tubuloglomerular feedback (increase GFR -> increased solute in macula densa -> decrease in resistance) * Glomerulotubular balance
Term
 Glomerulotubular balance
Definition
 Increase GFR -> increased filtered load -> increased NA and H2O reabsorption by proximal tubules   *Glom sends signal to tubules to Δ **constant fraction of Na/H2O is reabsorbed from proximal tubule despite Δs in GFR
Term
 Direct effects of pressure/vol on Na excretion
Definition
 ↑ arterial pressure -> ↑ renal perfusion pressure -> ↑ medullary blood flow -> ↓ medullary tonicity -> ↑ renal interstitial hydrostatic pressure -> ↓H2O absorption from TDLH of juxtamedullary nephrons -> ↓ [Na] delivered to TALH -> ↓ Na retention -> ↑ Na excretion
Term
 Describe the Renin-Angiotensin system
Definition
 1. Angiotensinogen is produced in the liver and is cleaved by renin (produced in the kidney)--> 2. Angiotensin I 3. Angiotensin I is converted to Angiotensin II 4. Angiotensin II acts in two places     a. Leads to vasoconstriction     b. Leads to production of aldosterone         --> increased salt/ water retention        --> increased BP
Term
 What things decrease the secretion of renin?
Definition
 1. Increased angiotensin 2. Increased ECF 3. Increasd Systemic arterial pressure 4. Increased TPR/ vasoconstriction 5. Increased aldosterone 6. Increased Na retention 7. Increased GFR/ decreased proximal reabs. of Na 8. Change in sodium at macula densa
Term
 What is the mechanism of Angiotensin II-mediated increase in proximal tubule reabsorption?
Definition
Term
 Action of angiotensin II
Definition
 Renal -Increase Na reabsorp in proximal tubules thru direct effect ( ) and through increased filtration fraction (via increased plasma oncotic P to favor reabsorption) -Increase sensivity of tubuloglomerular feedback -Decreased renin secretion -Decrease medullary blood flow   Extrarenal -Arteriolar vasoconstriction -Increase aldosterone -Increase ADH secretion -Increase thirst
Term
 What are the two most important factors leading to aldosterone secretion?
Definition
 1. Increase in [angiotensin II] 2. Increase in plasma [K] 3.
Term
 Cellular mechanism of aldosterone action
Definition
 Aldosterone binds receptor in cytosol --> goes to nucleas --> change in gene expression --> increase in expression/activity of ENaC and in Na/K ATPase *Increased Na reabsorption **Ramps up system
Term
 Time course of aldosterone action
Definition
 Latent pahse: 1/2 hr before response Early phase: Increase in proteins that increase the activity of ENaC Late phase: Increase in ENaC/ NaATPase  gene expression
Term
 Atrial Natiuretic Peptide
Definition
 1. Secreted in response to increase in blood pressure and ECF volume 2. Decreases blood pressure by decreasing TPR and enhancing NaCl and H2O secretion 3. Inhibits NaCl reabsorption by medullary portion of collecting duct 4. Inhibits ADH stimulated water reabsorption in collecting ducts 5. Inhibits ADH secretion from posterior pituitary
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