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APHY 201 Exam 4c1
Ch. 17 Drills: (Renal)'s Harder Questions
| Question | Answer |
|---|---|
| (starred) What is the pathway of blood through the renal blood vessels? | renal artery to segmental arteries, interlobar arteries, arcuate arteries, interlobular arteries, afferent arterioles, glomerulus, efferent arterioles, peritubular capillaries, interlobular veins, arcuate veins, interlobar veins, and renal vein. |
| any small amounts of what that filter out are almost entirely reabsorbed in the proximal convoluted tubule by active receptor-mediated endocytosis? | proteins |
| What are the potential effects of abnormal Glomerular Filtration Rates? (if it's higher or lower) | If GFR increases, dehydration and electrolyte depletion can occur from high urine output; if GFR decreases, wastes are reabsorbed, potentially causing azotemia. |
| How does Angiotensin II work to increase blood volume and systemic blood pressure? (3 things) | It enhances NaCl and water reabsorption by lowering peritubular capillary pressure, directly stimulating the proximal convoluted tubule, and stimulating the secretion of aldosterone and ADH. |
| What percent of unregulated water reabsorption occurs in the nephrons? (2 structures are responsible) | 85% of reabsorption occurs in the proximal tubules (65%) and the descending loop of Henle (20%). |
| How do cells of the proximal tubules maintain a lower sodium concentration than the filtrate? | They maintain lower concentration due to Na+/K+ pumps on their basal side and a generally low permeability to sodium. |
| How does the ascending limb of the loop of Henle move the ions around (which direction do the various ions go? | Salt is pumped out ascending limb, but walls are impermeable to water. Na+ moves down its gradient from filtrate into tubule cells; Cl- and K+ 2° transport by Na+-K+-2Cl- cotransport. Na+ is pumped out, Cl- follows, and K+ diffuses back into filtrate |
| How does urea contribute to the countercurrent system in the kidneys? | Urea is transported out of the collecting duct and diffuses back into the ascending limb, helping to increase the osmolarity of the deep medulla to reach a maximum concentration of 1200 mOsm. |
| In the proximal tubule, is there active transport of a solute involved, and is water passively transported? | Na+ is actively transported, and water is passively transported. |
| In the descending limb of the nephron loop, is there active transport of a solute involved, and is water passively transported? | There is no active transport, but water is passively transported. |
| In the thin segment of the ascending limb, is there active transport of a solute involved, and is water passively transported? | There is no active transport, and no passive water transport. |
| In the thick segment of the ascending limb, is there active transport of a solute involved, and is water passively transported? | Na+ is actively transported, but no water is passively transported. |
| In the distal tubule, is there active transport of a solute involved, and is water passively transported? | Na+ is actively transported, and no water is passively transported except in the last part of the tubule that is permeable to water. |
| What happens when ADH binds to receptors on the collecting duct cells? | It triggers cAMP and protein kinase, causing vesicles containing aquaporin channels to fuse to the plasma membrane and allow water to exit via osmosis. |
| How does the body regulate ADH when blood osmolality increases due to dehydration? (what receptor, does ADH go up or down, and does urine volume go up or down) | Osmoreceptors in the hypothalamus react, ADH secretion is increased, and urine volume decreases. |
| How does the body regulate ADH when blood osmolality decreases due to water uptake? (what receptor, does ADH go up or down, and does urine volume go up or down) | Osmoreceptors in the hypothalamus react, ADH secretion is decreased, and urine volume increases. |
| How do stretch receptors in the left atrium influence ADH secretion when blood volume goes up? (what receptor, does ADH go up or down, and does urine volume go up or down) | They react to the stretch, causing ADH secretion to decrease and urine volume to increase. |
| How do stretch receptors in the left atrium influence ADH secretion when blood volume goes down? (what receptor, does ADH go up or down, and does urine volume go up or down) | They react to the drop in volume, causing ADH secretion to increase and urine volume to decrease. |
| What is the difference between central and nephrogenic diabetes insipidus? | Central diabetes insipidus is caused by inadequate ADH secretion, whereas nephrogenic diabetes insipidus is the kidneys' inability to respond to ADH. |
| What are common causes of nephrogenic diabetes insipidus? | It can be caused by genetic defects in aquaporin channels or ADH receptors, or acquired from drug therapy such as lithium. |
| How is the excretion rate calculated and what does it measure (abbreviation)? | The excretion rate is calculated as (filtration rate + secretion rate) - reabsorption rate, and it is used to measure the glomerular filtration rate (GFR). |
| What are the membrane carriers that transport foreign molecules like drugs into the tubules for excretion? | They are called organic anion transporters (OATs) or organic cation transporters (OCTs). |
| Why is creatinine's renal plasma clearance slightly greater than the true GFR? | Creatinine is filtered and not reabsorbed, but it is slightly secreted by the tubules. |
| What does a blood urea nitrogen (BUN) test measure? | It measures the ratio of the plasma concentrations of urea to creatinine to provide additional information about kidney health. |
| What happens to a substance during filtration and how does it affect clearance? | The substance enters the glomerular ultrafiltrate, and some or all of it may enter the urine and be cleared from the blood. |
| What happens during reabsorption and how does it affect the clearance rate? | A substance is transported from the filtrate back into the blood, which decreases the clearance rate to less than the GFR. |
| What happens during secretion and how does it affect renal plasma clearance? | A substance is transported from peritubular blood into the filtrate, causing its renal plasma clearance to be greater than the GFR. |
| Why is para-aminohippuric acid (PAH) injected to measure total renal blood flow? | PAH is completely cleared in a single pass (20% filtered and 80% secreted), so its clearance of about 625 mL/min indicates total renal blood flow. |
| Where and how is glucose completely reabsorbed in the kidneys? | Glucose is completely reabsorbed in the proximal convoluted tubule via secondary active transport with sodium, facilitated diffusion, and simple diffusion. |
| How does extra glucose in the blood affect water reabsorption? | Extra glucose results in decreased water reabsorption from the filtrate, leading to possible dehydration. |
| How do kidneys maintain electrolyte and acid-base balance in the body? | The kidneys match the excretion of electrolytes (Na+, K+, Cl−, bicarbonate, phosphate) to their ingestion. |
| Why is the control of sodium (Na+) and potassium (K+) levels important? what do they regulate? | Na+ control regulates blood pressure and volume, while K+ control is vital for healthy skeletal and cardiac muscle activity. |
| How much of the filtered Na+ and K+ is reabsorbed early in the nephron without regulation? | About 90% of filtered Na+ and K+ is reabsorbed early in the nephron. |
| Where in the nephron does aldosterone control the regulated reabsorption of Na+ and secretion of K+? (2 substructures named) | Aldosterone controls this in the distal tubule and collecting duct. |
| What is the aldosterone-independent response to an increase in blood K+? | An increase in blood K+ directly triggers an increase in K+ channels in the cortical collecting duct, which are removed when K+ levels drop. |
| What is the aldosterone-dependent response to an increase in blood K+? | High K+ triggers the adrenal cortex to release aldosterone, which increases K+ secretion in the distal tubule and collecting duct. |
| What directly and indirectly stimulates the secretion of aldosterone? | A rise in blood K+ directly stimulates the adrenal cortex, while a fall in blood Na+ indirectly stimulates it via the renin-angiotensin-aldosterone system. |
| How do low salt levels lead to the secretion of renin? | Low salt levels inhibit ADH secretion, reducing blood volume, which is detected by granular cell baroreceptors that then secrete renin. |
| What is B-type natriuretic peptide (BNP) and why is it measured clinically? | BNP is a hormone released by the heart's ventricles in response to increased volume and pressure, and its levels are measured to help diagnose congestive heart failure. |
| How do rising potassium levels affect the regulation of renin and aldosterone? | Rising K+ has no effect on renin or angiotensin II, but directly stimulates the adrenal cortex to increase aldosterone secretion. |
| (starred) How does the reabsorption of Na+ relate to the secretion of K+ and H+? | Reabsorption of Na+ stimulates the secretion of K+ and H+ due to electrostatic attraction, and K+ and H+ compete for secretion via antiport pumps. |
| (starred) How does primary hyperkalemia lead to acidosis? | Hyperkalemia stimulates the secretion of K+ and inhibits the secretion of H+, which leaves excess acid in the blood. |
| Which structure uses Na+/H+ pumps in the apical surface of its cells to regulate acid-base balance? | The proximal convoluted tubule uses secondary active transport Na+/H+ pumps to pull Na+ into the cells and kick H+ out into the tubular fluid.Which pumps are primarily responsible for acidifying the urine in the distal convoluted tubule? |
| How do the kidneys compensate for respiratory alkalosis? | Less H+ is available to transport bicarbonate, so less bicarbonate is reabsorbed, and the extra bicarbonate secretion makes the blood more acidic. |
| How do the kidneys compensate for respiratory acidosis? | The proximal tubule metabolizes glutamine into ammonia and new bicarbonate, which enters the blood to neutralize acid while the ammonia buffers H+ in the urine. |
| (starred) what is the mechanism of action and major site of action for loop diuretics? | inhibits sodium transport at the thick segments of ascending limbs |
| (starred) what is the mechanism of action and major site of action for thiazides? | inhibits sodium transport at the last part of ascending limb and first part of distal tubule |
| (starred) what is the mechanism of action and major site of action for CAH inhibitors? | inhibits reabsorption of bicarbonate at the proximal tubule |
| (starred) what is the mechanism of action and major site of action for osmotic diuretics? | reduces osmotic reabsorption of water by reducing osmotic gradient at the last part of distal tubule and cortical collecting duct |
| (starred) what is the mechanism of action and major site of action for potassium-sparing diuretics? (split) | can inhibit action of aldosterone or inhibit Na+ reabsorption and K+ secretion; in the last part of distal tubule and cortical collecting duct |
| How do loop diuretics like Lasix work? | Loop diuretics are the most powerful diuretics and inhibit up to 25% of water reabsorption by inhibiting salt transport out of the ascending loop of Henle. |
| How do thiazide diuretics work? | Thiazide diuretics inhibit salt transport in the distal tubule and can inhibit up to 8% of water reabsorption. |
| What is the function of carbonic anhydrase inhibitors as diuretics? | They are weaker diuretics that inhibit water reabsorption when bicarbonate is reabsorbed and also promote the excretion of bicarbonate. |
| How do osmotic diuretics like Mannitol reduce water reabsorption? | Osmotic diuretics reduce water reabsorption by adding extra solutes to the filtrate, a mechanism that can also happen as a side effect of diabetes mellitus when extra glucose is present. |
| How do potassium-sparing diuretics function? | They act as aldosterone receptor antagonists to block the reabsorption of sodium and the secretion of potassium. |
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