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74 Cards in this Set
- Front
- Back
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How much of total body kg is water?
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60%
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How much water is intra vs extracellular?
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2/3 = ICF
1/3 = ECF |
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ECF is split between:
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.25 plasma
.75 ISF |
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How do you calculate ICF?
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TBW - ECF
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How do you calc Interstitial fluid volume?
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Need to know total Extracell fluid vol. ECF - Plasma
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60-40-20 rule:
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60% of body weight = TBW
40% of body weight = ICF 20% of body weight = ECF |
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Is there more water INSIDE your cells or outside?
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INSIDE - 2/3
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What is used to measure plasma volume?
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Radiolabeled albumin
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What is used to measure ECF volume?
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Inulin
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What is normal osmolarity?
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290 mOsm
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What is renal clearance?
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Vol of urine from which a substance is completely cleared per unit time
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Calculate Renal clearance:
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Cx = UxV/Px
Urine amt x urine flow rate divided by plasma amt of x |
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Filtration by glomerulus is based on:
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Size/charge
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What gives the glomerulus its neg charge?
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Heparan sulfate
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When is the charge barrier lost?
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Nephrotic syndrome
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3 components of the GBM:
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-Fenestrated caps - size
-BM w/ heparan sulfate - chrg -Epithelial Podocyte foot processes |
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What is used to calculate GFR?
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Inulin (fully filtered, not reabsorbed, not secreted.
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How do you use inulin to calculate GFR?
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Just calculate clearance of inulin
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What else is an approximate measure of GFR?
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Creatinine clearance
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How do you calculate GFR based on pressures?
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kf(Pgc - Pbs)-(pigc - pibs)
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What is the normal oncotic pressure in BS?
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zero
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What can be used to measure effective plasma renal flow?
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PAH - para amino hippurate
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Why is PAH able to estimate effective RPF?
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Because it is both FILTERED and ACTIVELY SECRETED into the PCT; all is excreted
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How do you calculate ERPF based on PAH then?
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Just calculate clearance of PAH
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How does renal plasma flow relate to renal bloodflow?
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RBF = RPF/1-HCt
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How close is the effective RPF as measured by PAH to the true RPF?
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It underestimates it but only by about 10%
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What is FF?
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FF = GFR/RPF
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What is the Filtered LOAD?
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GFR x Plasma conc
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How does constricting the Afferent arteriole affect
-RPF -GFR -FF |
Decrease RPF
Decrease GFR No effect on FF |
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How does dilating the Afferent arteriole affect
-RPF -GFR -FF |
Increase RPF
Increase GFR Still no effect on FF |
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What dilates the renal afferent artiole?
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Prostaglandins
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How does constricting the Efferent arteriole affect
-RPF -GFR -FF |
-Decrease RPF
-Increase GFR -Increase FF |
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What preferentially constricts the efferent arteriole?
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Ang II
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What will inhibit this from happening?
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An ACE inhibitor (captopril, enalapril, lisinopril)
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How does increasing plasma protein affect
-RPF -GFR -FF |
RPF - no change
GFR - DECREASE FF - decrease |
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How does decreasing plasma protein affect RPF/GFR/FF?
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RPF - no change
GFR - increase FF - increase |
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How will constricting the ureter affect RPF/GFR/FF?
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NC on RPF
Decrease GFR Decrease FF |
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What do you need to calculate Free Water Clearance?
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-Urine flowrate
-Urine osmolarity -Plasma osmolarity |
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How do you calculate FWC?
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V - Cosm (clearance of osmoles)
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How do you calculate clearance of osmoles?
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Cosm = (Uosm x V)/Posm
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What happens to glucose normally in the kidney?
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It is completely reabsorbed by the proximal tubules
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When does glucose start to NOT be completely reabsorbed?
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At 200 mg/dl - the Threshold
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When is glucose transport and reabsorption SATURATED?
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At 350 mg/dl
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What is the workhorse of the nephron?
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The early PCT!
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What does the early PCT reabsorbe?
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-All glucose
-All amino acids -Most sodium/bicarb/water |
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Does the early PCT secrete anything?
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Yes - ammonia to act as a buffer for secreted H+
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How does the early PCT reabsorb glucose?
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With a Na/Glu symporter
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How does the early PCT reabsorb Bicarb?
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By converting CO2 into H2CO3, then secreting H+ back into the lumen as HCO3 diffuses into the blood.
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How does the early PCT secrete acid?
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In exchange for Na
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For every molecule of bicarb reabsorbed in the early PCT:
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One H+ must be excreted
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What keeps the gradient for Na to be reabsorbed by the early PCT?
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Na/K ATPase on the basolateral membrane!
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What happens in the thin descending loop of Henle?
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Passive reabsorption of water
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How is water passively reabsorbed?
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Because the medulla is hypertonic and water wants to go where the solutes are
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What is reabsorbed in the thick asc LOH?
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-Na/K/2Cl
-Mg/Ca |
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How is Na/K/2Cl reabsorbed?
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ACTIVELY
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How are Mg/Ca2+ reabsorbed?
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indirectly by the reabsorption of all the other ions which leaves a pos charge in the lumen to push the other divalent cations into the cell
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Anything with water in the thick asc LOH?
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No it's impermeable
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What happens in the early distal convoluted tubule?
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Active reabsorption of Na/Cl
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What else MAY be reabsorbed under the control of water hormone in the early distal Convoluted tubule?
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Ca2+ - under influence of PTH
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What are the 2 important cell types in the collecting duct?
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-Principal cells
-Intercalated cells |
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What are the principal cells responsible for?
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Reabsorption of Na in exchange for K or H secretion
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What controls Na/K exchange at the principal cells?
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Aldosterone
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What other important process occurs in the Principal cells?
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Water reabsorption
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What is water reabsorption controlled by in the principal cells?
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ADH
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Where is the Aldosterone receptor at the principal cells?
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INTRACELLULAR - it is a hormone response element!
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What effect does Aldo have when binding its intracell receptor at the principal cell?
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Upregulates expression of Na/K ATPase at the basolateral surface
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What effect does ADH have on the principal cells?
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Increases the expression of aquaporins at the LUMENAL surface
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What happens at the lumenal side of the Intercalated cells of the collecting duct?
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Na/H ATPase exchange secretes acid
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What happens at the basolateral side of the Intercalated cells?
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HCO3/Cl exchange to reabsorb 1 bicarb for every H secreted
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So at the start of the prox tubule, what is the TF/P ratio of everything?
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1 - the same amt should be in the tubule fluid as in the plasma
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What happens to osmolarity of fluid in the proximal tubule as things get reabsorbed?
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NOTHING - it remains isosmotic to plasma
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Why doesn't osmolarity change?
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Because most water is reabsorbed too
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What gets SECRETED at the proximal tubule?
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PAH
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What gets neither secreted NOR reabsorbed?
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Inulin
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