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89 Cards in this Set
- Front
- Back
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↑ glomerular pressure, ↓ peritulbuar pressure, ↓ RPF
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Efferent arteriole constriction
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↓ glomerular pressure, ↑ peritubular pressure, ↑ RPF
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Efferent arteriole dilation
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↓ glomerular pressure, ↓ peritulbuar pressure, ↓ RPF
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Afferent arteriole constriction
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↑ glomerular pressure, ↑ peritulbuar pressure, ↑ RPF
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Afferent arteriole dilation
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Afferent arteriole dilation
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↑ glomerular pressure, ↑ peritulbuar pressure, ↑ RPF, ↑ GFR
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Afferent arteriole constriction
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↓ glomerular pressure, ↓ peritulbuar pressure, ↓ RPF, ↓ GFR
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Efferent arteriole dilation
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↓ glomerular pressure, ↑ peritubular pressure, ↑ RPF, ↓ GFR
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Efferent arteriole constriction
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↑ glomerular pressure, ↓ peritulbuar pressure, ↓ RPF, ↑ GFR, ↑ FF
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Plasma oncotic pressure changes as blood flows through the nephron
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Oncotic pressure increases because filtered fluid increases protein concentration. Oncotic pressure is resposible for peritubular reabsorption
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Normal capillary hydrostatic pressure of the glomerulus
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45 mmHg
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Normal capillary oncotic pressure of the glomerulus
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27 mmHg
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Normal hydrostatic pressure of bowman's capsule
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10 mmHg
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Normal GFR value
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120 ml/min
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Normal RPF value
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600 ml/min
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Normal filtration fraction value
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FF = GFR/RPF = 120mi/min / 600ml/min = 0.20
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Effect of sympathetic stimulation in the nephron
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↓ GFR, ↑ FF, ↑ peritubular reabsoption
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Effect of angiotensin II in the kidney
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Vasoconstriction of the efferent arteriole more than afferent --> maintains GFR
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Filtered load
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Rate at which a substance filters into Bowman's capsule = FL = GFR x Free plasma concentration
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Excretion of a substance in the urine
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Excretion = filtered load + (amount secreted - amount reabsorbed) = filtered load + transport OR urine concentration X urine flow rate
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Characteristics of a Tm system
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Carriers become saturated, carriers have high affinity, low back leak. The filtered load is reabsorbed until carriers are saturated - the excess is excreted.
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Renal treshold for glucose
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180 mg/dl or 1.8 mg/ml. Represents the beginning of splay.
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Tm rate of reabsorption of glucose
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375 mg/min. Represents the maximum filtered load that can be reabsorbed when all carriers in the kidney are saturated (end of splay region).
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Glucose reabsorption graph
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At normal glucose levels, the amount filtered is the same as the amount reabsorbed. At threshold (beginning of splay), the excretion curve starts to ascend and the amount filtered exceeds the amount reabsorbed.
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Substances that are reabsorbed using a Tm system
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Glucose, amino acids, small peptides, myoglobin, ketones, calcium, phosphate.
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Characteristics of a gradient-time system
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Carriers are not saturated, carriers have low affinity, high back leak
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Substances that are reabsorbed using a gradient-time system
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Sodium, potassium, chloride and water
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Substances secreted using a Tm system
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PAH. 20% filtered, 80% secreted.
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Graph for PAH secretion
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At low plasma concentration secretion is 4 times the filtered load. When carriers become saturated, secretion reaches a plateau and the amount excreted is proportional to the amount filtered.
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How is the net transport rate for a substance calculated?
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Net transport rate = filtered load - excretion rate = (GFR X Px) - (Ux X V)
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Effects of blood pressure changes in the kidney
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GFR and RBF are maintained constant within the autoregulatory range. Urine flow is directly proportional to blood pressure due to pressure natriuresis and pressure diuresis.
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What is clearance and how is it calculated?
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It's the volume of plasma cleared of a substance over time. Clearance = excretion / Px = Ux X V / Px
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Characteristics of glucose clearance
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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.
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Characteristics of inulin clearance
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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.
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Characteristics of creatinine clearance
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A constant amount of creatinine is cleared regardless of plasma concentration, but creatinine clearance is more than GFR because some is always secreted.
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Characterisics of PAH clearance
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As plasma concentration increases, clearance decreases because carriers that mediate active secretion become saturated. At normal levels, PAH clearance = RPF because all is excreted.
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How is GFR calculated using inulin?
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GFR is equal to inulin clearance because it's only filtered and none is secreted nor reabsorbed. Cin = GFR = Uin X V / Pin
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How is creatinine production calculated?
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Creatinine production = creatinine excretion = filtered load of creatinine = [Cr]p X GFR. Creatinine is filtered and secreted, not reabsorbed.
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How does inulin concentration change as it passes through the nephron?
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Inulin becomes more concentrated as it passes through the tubules because water is being reabsorbed and not inulin.
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Gold standard to measure GFR
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Inulin clearance because it's filtered but not secreted nor reabsorbed.
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Gold standard to measure RPF
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PAH clearance because some is filtered and the remaining is all secreted.
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How is effective RPF calculated?
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PAH clearance = RPF = Upah X V / Ppah
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How is renal blood flow calculated?
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ERPF / 1-Hct; ERPF = Upah X V / Ppah
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What does positive free water clearance mean?
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Water is being eliminated. Hypotonic urine is being formed to increase plasma osmolarity.
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What does negative free water clearance mean?
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Water is being conserved. Hypertonic urine is being formed to lower plasma osmolarity.
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How is free water clearance calculated?
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V - (Uosm(V) / Posm)
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Which substance is cleared the most: PAH, inulin, glucose, creatinine
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PAH
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Which substances are cleared more than glucose?
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Sodium, inulin, creatinine, PAH
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Which substance is cleared the least: PAH, inulin, glucose, creatinine
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Glucose
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Which substances are cleared more than inulin?
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Creatinine, PAH
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Which substances are cleared less than creatinine?
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Inulin, glucose, sodium
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Transporters in the luminal membrane of the proximal tubule
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Secondary Na/glucose cotransporter, secondary Na/amino acid cotransporter, secondary Na/H countertransporter
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What substances are reabsorbed in the proximal tubule and how much?
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Na (2/3 of filtered load), glucose (100%), amino acids (100%), HCO3 (indirectly, 80%), H20 (2/3), K (2/3), Cl (2/3)
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Tubular osmolarity at beginning and end of proximal tubule
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At the beginning and end is isotonic with plasma but only 1/3 of the filtered load.
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Transporters in the basal membrane of proximal tubule
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Na/K ATPase - luminal membrane secondary Na transporters depend on this.
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Transporters in the basolateral membrane of proximal tubule
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Na/K ATPase - luminal membrane secondary Na transporters depend on this.
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Most energy-dependant process in the nephron
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Active reabsorption of Na by the basal and basolateral Na/K ATPase
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Characteristics of the loop of henle
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Descending limb is permeable to water so water difuses out and intraluminal osmolarity increases to 1,200mOsm Ascending limb is impermeable to water and Na is actively pumped out by Na/K/2Cl pump so fluid becomes hypotonic. Flow is slow, anything that increases flow, decreases capacity to concentrate urine.
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Characteristics of the collecting duct
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Impermeable to water unless ADH is present. ADH increases permeability to H20 and urea to concentrate urine. Tight junctions with little back-leak.
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Specialized cells of the distal tubule and collecting duct
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Principal cells (aldosterone) and intercalated cells (create HCO3)
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Actions of principal cells of the distal tubule and collecting duct
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Aldosterone increases Na receptors in the membrane and increases primary transport by Na/K ATPase. Secondary transport of Na and secretion of K.
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Actions of intercalated cells of the distal tubule and collecting duct
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Acidify the urine and produce new bicarbonate
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Actions of the distal tubule and collecting duct
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Reabsorption of Na and secretion of K (stimulated by aldosterone), acidification of the urine (secretion of H and creation of HCO3)
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Urine buffer systems
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H2PO4- (dihydrogen phosphate) (tritratable acid) buffers 33% of secreted H. NH4+ (amonium) (nontritratable acid) buffers the remaining secreted H.
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How is potassium affected by acidosis?
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High concentration of ECF H --> H diffuses to ICF --> K diffuses to ECF --> hyperkalemia
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How is potassium affected by alkalosis?
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Low concentration of ECF H --> H diffuses to ECF --> K diffuses to ICF --> hypokalemia
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Potassium dynamics in acute alkalosis
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Hypokalemia, ↑ intracellular K, ↑ renal K excretion, negative K balance
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Potassium dynamics in chronic alkalosis
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Hypokalemia, ↓ intrecellular K, ↑ renal K excretion, negative K balance
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Potassium dynamics in acute acidosis
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Hyperkalemia, ↓ intracellular K, ↓ renal K excretion, positive K balance
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Potassium dynamics in chronic acidosis
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Hyperkalemia, ↓ intracellular K, ↑ renal K excretion, negative K balance
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How is potassium balance in acute acidosis?
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Positive (potassium is reabsorbed)
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How is potassium balance in acute alkalosis?
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Negative (potassium is excreted)
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How is potassium balance in chronic alkalosis?
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Negative (potassium is excreted)
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How is potassium balance in chronic acidosis?
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Negative (potassium is excreted)
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How is plasma potassium concentration in alkalosis?
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Hypokalemia
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How is plasma potassium concentration in acidosis?
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Hyperkalemia
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What is the difference in potassium dynamics between acute and chronic alkalosis?
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Acute alkalosis --> ↑ intracellular K; Chronic alkalosis --> ↓ intracellular K
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What is the difference in potassium dynamics between acute and chronic acidosis?
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Acute acidosis --> ↓ renal K excretion, positive K balance; Chronic acidosis --> ↑ renal K excretion, negative K balance
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Changes in respiratory acidosis
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Hypoventilation --> ↑ PaCO2 --> ↑ H and slight ↑ in HCO3 --> ↓ pH
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Changes in respiratory alkalosis
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Hyperventilation --> ↓ PaCO2 --> ↓ H and HCO3 --> ↑ pH
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Changes in metabolic acidosis
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Gain of H or loss of HCO3 --> ↓ HCO3 --> ↓ pH. To see if gain of H or loss of HCO3 check anion gap.
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Changes in metabolic alkalosis
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Loss of H or gain in HCO3 --> ↑ HCO3 --> ↑ pH. To see if gain of H or loss of HCO3 check anion gap.
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Normal values of PCO2, HCO3 and pH
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pH = 7.4; PCO2 = 40mmHg; HCO3 = 24mmol/L
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↑pH, ↑ HCO3, ↑PCO2, ↓PO2, alkaline urine
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Partially compensated metabolic alkalosis
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↓pH, ↑PCO2, ↑HCO3, ↓PO2, acid urine
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Partially compensated respiratory acidosis
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↑pH, ↓PCO2, ↓HCO3, normal PO2, alkaline urine
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Partially compensated respiratory alkalosis
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↓pH, ↓PCO2, ↓HCO3, normal PO2, acid urine
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Partially compensated metabolic acidosis
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Normal plasma anion gap value
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PAG = 12
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Conditions that increase plasma anion gap
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Lactic acidosis, ketoacidosis, ingestion of salicylate
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Hyperchloremic non-anion gap metabolic acidosis
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Loss of HCO3 (as in diarrhea) causes increases absorption of solutes and water, increasing Cl. Therefore ↓HCO3 and ↑Cl with a plasma anion gap of 12.
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