Identify (A), (B), and (C), which are actively absorbed into the thick tubule cell, and (D) and (E), which are passively reabsorbed.
(A) sodium; (B) potassium; (C) two chloride ions; (D) magnesium; (E) calcium
Elevated parathyroid hormone increases exchange of (A) and (C) between cell and blood. How does this affect uptake of (C) from the lumen?
(A) sodium; (C) calcium; increased exchange reduces intracellular calcium and allows more luminal calcium to be reabsorbed
Hydrochlorothiazide inhibits the active reabsorption of (A) and (B) from the lumen. How does this affect tonicity of the urine?
The absorption of (A) sodium and (B) chloride helps to make the urine hypotonic; inhibition of this process makes the urine more hypertonic
In Gitelman syndrome, early distal convoluted tubules do not actively reabsorb (A) and (B). How does this affect reabsorption of (C)?
More reabsorption; less intracellular Na+ from less pumping increases (A/C) Na+/Ca2+ exchanger activity, increasing (C) Ca2+ reabsorption
Nonwater mass comprises _____% of total body weight (in kilograms), while total body water (in liters) makes up _____% of total body weight.
40% nonwater mass; 60% total body water
What fraction of total body water is extracellular vs intracellular fluid?
One third extracellular fluid, two thirds intracellular fluid
What fraction of the extracellular fluid is plasma volume vs interstitial volume?
One fourth plasma volume, three fourths interstitial volume
What substance is used to measure plasma volume?
What substance is used to measure extracellular volume?
What is the 60-40-20 rule of body weight?
60% of total body weight is made up of total body water, 40% is made up of intracellular fluid, and 20% is made up of extracellular fluid
What is the normal value for plasma osmolarity?
Extracellular fluid consists of _____ (high/low) sodium chloride and _____ (high/low) potassium, whereas intracellular fluid consists of _____ (high/low) sodium chloride and _____ (high/low) potassium.
High; low; low; high (remember: HIKIN': HIgh K INtracellular)
What are the two characteristics on which the glomerular barrier bases plasma filtration?
Size and net charge of plasma molecules
The fenestrated capillary endothelium of the glomerular filtration barrier is responsible for the filtration of plasma by what characteristic, size or charge?
The fused basement membrane of the glomerulus containing heparan sulfate is responsible for the filtration of plasma molecules by which characteristic, size or charge?
What kind of charge does heparan sulfate have?
Negative; as a result, negatively charged proteins are kept in plasma
The epithelial layer of the glomerular filtration barrier is formed by which cells?
Podocyte foot processes
What are the three components of the glomerular filtration barrier?
Fenestrated capillary endothelium (size barrier), fused basement membrane with heparan sulfate (negative charge barrier), and epithelial layer that consists of podocyte foot processes
Albuminuria, hypoproteinemia, generalized edema, and hyperlipidemia are hallmarks of what syndrome?
Nephrotic syndrome; resulting from loss of the charge barrier in the glomeruli
What is the formula for calculating the clearance of substance x, the volume of plasma from which the substance is cleared completely per unit of time?
Renal clearance of x = the urine concentration of x times the urine flow rate divided by the plasma concentration of x (Cx = Ux × V/Px)
If renal clearance is less than the glomerular filtration rate of substance x, then there is net tubular _____ (reabsorption/secretion) of x.
If renal clearance is greater than the glomerular filtration rate of substance x, then there is a net tubular _____ (reabsorption/secretion) of x.
Why is para-aminohippurate used to estimate renal plasma flow?
Para-aminohippurate is actively secreted from the proximal tubule into the urine; the concentration of para-aminohippurate in the renal vein is zero
The clearance of what substance is used to estimate renal plasma flow?
What is the formula for estimating the effective renal plasma flow using para-aminohippuric acid?
Effective renal plasma flow = urine concentration of para-aminohippuric acid times the urine flow rate divided by the plasma concentration of para-aminohippuric acid (UPAH × V/PPAH)
What is the formula for estimating renal blood flow if renal plasma flow is known?
Renal blood flow = renal plasma flow divided by (1 - the hematocrit), or RBF = RPF/(1 - Hct); in a normal individual, renal blood flow will be approximately double the renal plasma flow
Effective renal plasma flow _____ (over-/under-) estimates true renal plasma flow by approximately _____%.
Under; 10; it is an underestimate because 10% of renal blood flow perfuses the kidney parenchyma rather than being filtered through the glomerulus
How is the filtration fraction for a molecule determined?
By determining the ratio of the glomerular filtration rate to renal plasma flow
What are the effects of prostaglandins on the glomerulus?
Prostaglandins cause dilation of the afferent arteriole and an increased glomerular filtration rate
What are the effects of angiotensin II on the glomerulus?
Angiotensin II causes constriction of the efferent arteriole and increased glomerular filtration rate