AP 18 Nov 24 Lecture 31 Flashcards
How is renal plasma flow determined using PAH?
Renal plasma flow is determined by measuring the clearance of PAH (para-aminohippuric acid) and involves comparing venous and arterial concentrations of PAH.
What percentage of PAH is typically removed by the kidneys?
The kidneys can remove about 90% of PAH as blood passes through them.
What role does the macula densa play in regulating GFR?
The macula densa helps adjust or auto-regulate GFR through the release of renin and nitric oxide, affecting the resistance of afferent and efferent arterioles.
How does angiotensin II affect the arterioles?
Angiotensin II preferentially constricts the efferent arteriole while causing relaxation of the afferent arteriole, leading to a reduction in afferent resistance.
What is the effect of drugs that relax blood vessels on GFR?
Drugs that relax blood vessels, such as calcium channel blockers and nitric oxide donors, typically preferentially affect the afferent arteriole, which can increase GFR.
What happens to sodium reabsorption in the proximal tubule when angiotensin II binds to its receptors?
Angiotensin II binding increases the activity of sodium-potassium ATPase pumps in the proximal tubule, enhancing sodium reabsorption.
How is bicarbonate reabsorbed in the proximal tubule?
Bicarbonate is reabsorbed in the proximal tubule primarily through a sodium-bicarbonate symporter, which moves sodium and bicarbonate out of the cell simultaneously.
What is bulk flow in the context of renal physiology?
Bulk flow refers to the process of reabsorption in the peritubular capillaries, driven by capillary forces, allowing for significant reabsorption of fluids and solutes.
What is the role of urea in the renal interstitium?
Urea helps create a concentrated renal interstitium, facilitating water reabsorption via osmosis.
What are the two pathways for reabsorption in the proximal tubule?
Reabsorption occurs through paracellular pathways (between cells) and transcellular pathways (through cell membranes).
What is the role of the renal interstitium in water retention?
The renal interstitium helps hold on to as much water as possible by packing solids to assist with osmosis.
What are the pathways involved in substance movement in the kidneys?
Substance movement in the kidneys occurs via transcellular pathways, passive diffusion, and paracellular pathways.
What is the function of the brush border in proximal tubular cells?
The brush border increases the surface area of proximal tubular cells by about 20 fold, allowing for more transporters to be placed for reabsorption.
How does sodium move into proximal tubular cells?
Sodium moves into proximal tubular cells via an electrochemical gradient, which involves both concentration and electrical gradients.
What is the typical membrane potential in the kidney?
The typical membrane potential in the kidney is around negative 70 mV.
What happens to chloride concentration in the proximal tubule?
Chloride concentration tends to increase slightly as it follows sodium reabsorption, especially in the second half of the proximal tubule.
What is the role of the proximal tubule in protein reabsorption?
The proximal tubule reabsorbs about 1.7 grams of the 1.8 grams of protein filtered daily, using endocytosis to manage small amounts of filtered proteins.
What is endocytosis in the context of proximal tubular cells?
Endocytosis is the process by which proximal tubular cells engulf filtered proteins, breaking them down into amino acids for reabsorption.
How does the proximal tubule regulate acid-base balance?
The proximal tubule regulates acid-base balance primarily through the sodium-proton exchanger, which secretes protons and reabsorbs sodium.
What is the role of carbonic anhydrase in the proximal tubule?
Carbonic anhydrase facilitates the conversion of carbonic acid into carbon dioxide and water, aiding in bicarbonate reabsorption and pH regulation.
What is formed in the proximal tubule?
A bunch of carbonic acid is formed in the proximal tubule.
What role does carbonic anhydrase play in the proximal tubule?
Carbonic anhydrase speeds up the reaction of carbonic acid dissociating into CO2 and water.
What happens if the reaction of carbonic acid goes in the opposite direction?
Carbonic acid can dissociate into protons and bicarbonate.
What is the effect of carbonic anhydrase inhibitors?
They slow down the proton-sodium exchanger, leading to decreased bicarbonate reabsorption and potential acidosis.