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Which section of the nephron is known as the "workhorse?"
The proximal tubule.
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The proximal tubule reabsorbs ______ % of filtered fluid and NaCl.
65.
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True or False?
The proximal tubule of the nephron is the site of secretion of organic acids and bases.
True.
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True or False?
The proximal tubule of the nephron reabsorbs about 80% of filtered glucose and amino acids.
- False.
- 100% is reabsorbed.
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The osmolarity of the solution inside the proximal tubule is ___________, compared to the osmolarity of the solution in the interstitium.
Isosmotic. 300 mosmol.
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Explain why the processes that occur in the proximal tubule are known as "bulk reabsorption."
Because H2O follows the solutes as they are transported out.
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The thin descending loop of Henle is mostly permeable to what? How is it transported?
- Water.
- Passive diffusion into the hyperosmotic medullary interstitium.
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The thick ascending loop of Henle is permeable to what? Impermeable to what? How is it transported?
- Permeable to Na+, K+, and Cl-, by active transport.
- Impermeable to water.
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As fluid passes through the thin descending loop of Henle, its osmolarity (increases / decreases).
Increases.
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As fluid passes through the thick ascending loop of Henle, its osmolarity (increases / decreases).
Decreases.
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Describe the absorption characteristics of the early distal tubule.
Similar to the thick ascending loop of Henle (except there is no K+ reabsorption).
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Describe the absorption characteristics of the late distal tubule.
- Similar to those of the cortical collecting duct.
- Site for hormone action.
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True or False?
ADH acts all the way down the collecting duct, but Aldosterone only acts at the cortical collecting duct.
True.
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What is the result of ADH action along the collecting duct of the nephron?
ADH results in increased water reabsorption along the collecting duct and therefore a decrease in urine output.
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What is the physiological mechanism by which ADH increases H2O reabsorption?
When ADH binds to tubular epithelial cells of the LDT and collecting duct, aquaporons are placed on the apical surfaces of the epith. membranes.
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