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122 Cards in this Set
- Front
- Back
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what are the 3 basic functions of the nephrons?
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1. filtration
2. reabsorption 3.secretion |
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define filtration
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movement of wastes and other solutes across the glomerular capillaries into the capsule and then into the tubule.
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define reabsorption
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movement of fluid from the tubules and collecting duct back into the bloodstream
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define secretion
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removes certain substances from the blood into the fluid for excretion
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what does not cross into the renal capsule?
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plasma proteins, blood cells, and platelets.
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what volume of fluid is filtered in a day?
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180 liters
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what percentage of the cardiac output passes through the kidneys?
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20-25%
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what determines the filtration pressure?
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change in resistance in arterioles
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what volume of urine is produced in a day?
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1.5 liters/day
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what are the 3 components that make up the filtration membrane?
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1. glomerular endothelial cells
2. basal laminae 3. filtration slits |
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what are the three main pressures for filtration?
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1. glomerular blood hydrostatic pressure.
2. capsular hydrostatic pressure 3. blood colloid pressure. |
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how do you calculate net filtration pressure?
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GHP- BCOP-CHP = net filtration pressure
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autoregulation maintains a nearly constant GFR when mean arterial blood pressure is between?
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80-180 mm Hg
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what will happen to resistance, renal blood flow, capillary blood pressure, and the glomerular filtration rate if vasoconstriction occurs at the afferent arteriole?
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resistance increases
renal blood flow decreases capillary blood pressure decres GFR decreases |
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what will happen to resistance, renal blood flow, capillary blood pressure, and glomerular filtration rate is vasoconstriction occurs at the efferent arteriole?
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resistance increases
renal blood flow decreases capillary blood pressure increa GFR increases |
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what is filtration fraction?
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the percentage of blood volume into the tubule.
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what is the myogenic response?
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the intrinsic ability of vascular smooth muscle to respond to pressure changes (blood pressure)
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what is tubuloglomerular feedback?
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a local pathway in which fluid flow through the tubule influences GFR (by using Renin and paracrine signals)
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what do the macula densa cells in the juxtameduallary apparatus do?
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as salt delivery past the macula densa increases as a result of the increase in GFR. The macula densa cells send paracrine messages to neighboring afferent arteriole to constrict.
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what do the granular cells of the juxtamedullary apparatus do?
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secrete renin
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what is renin?
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an enzyme released from the juxtaglomerular cells that converts angiotensinogen to angiotensin I.
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how does neural control effect GFR?
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sympathetic neurons innervate afferent and efferent arterioles. Sym. innervation of the alpha receptors on vascular smooth muscle causes vasoconstriction.
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what are the renal types of GFR regulation?
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myogenic and tubuloglomerular regulation
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what is the neural GFR regulation?
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sympathetic innervation of the afferent and efferent arterioles
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what are the hormonal GFR regulations?
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angiotensin II and ANP
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what is angiotensin II?
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a potent vasoconstrictor activated by renin; triggers the release of aldosterone and ADH.
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what are the steps in converting angiotensinogen to angiotensin II?
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angiotensinogen
renin angiotensin I ace angiotensin II |
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what is ANP
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Atrial Natriuretic Peptide. from atria of the heart that regulates sodium and water excretion.
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how does filtrate move through the nephrron?
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bowmans capsule
proximal convoluted tubule descending loop of henle ascedning loop of henle distal convoluted tubule cortical collecting duct medullary collecting duct. |
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what is the sequence of blood flow from the renal artery to the renal vein?
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renal artery
segmental artery lobar artery interlobar artery arcuate artery interlobular artery afferent arteriole glomerulus efferent arteriole peritubluar capillaries vasa recta interlobular vein arcuate vein interlobar vein renal vein |
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what type of cells are in the PCT?
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brush border within a highly folded basolateral membrane. These cells have numerous transport proteins.
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what type of cells are in the descending loop of henle?
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flattened cells with few microvilli and transport proteins. These cells are permeable to water, but not the salt.
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what type of cells make up the ascending loop of henle?
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cells of this region have a glycoprotein covering of the luminal membrane and are permeable to salt but not water.
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what type of cells make up the late DCT and the cortical collecting duct?
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composed of principle and intercalated cells. Sodium and water reabsorption in this area are hormonally regulated.
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what type of cells make up the medullary collecting duct?
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this region is composed mainly of principle cells. Water permeablily is closely regulated by the antidiuretic hormone.
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define transcellular
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through the luminal and basolateral membrane
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define paracellular
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through tight junctions
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do most ions use the transcellular or paracellular pathway?
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transcellular
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define antiporter
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transports a protein in one direction for another specific substance moved in another direction
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passive transport
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a process that dosent require cellular energy to move across the cell membrane
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primary active transport
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process in which the energy liberated from ATP is transferred directly to the carrier molecule participating in the transport.
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secondary active transport
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process that uses imbalances created by primary active transport to move additional substances across the membrane. ATP is an indirect energy source for secondary active transport.
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symporter
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co-transports two different substances in the same direction.
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transport max.
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a point at which increases in concentration do not result in an increase in movement of a substance across a membrane.
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obligatory water reabsorption
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water reabsorption together with the solutes in tubular fluid.
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facultative diffusion
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a passive transport process that uses a carrier molecule to enable the passage of a complex molecule across the membrane.
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renal threshold
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a concentration of a substance within the blood which, when reached, causes the substance to appear in the urine.
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ion channel
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are pore forming proteins that help to establish and control the small voltage gradient across the plasma membrane of all living cells by allowing the flow of ions down their electrochemical gradient.
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coupled transport
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the linked coupled transport of two substances. If the substances are going in the same direction- symport if they are going in opposite directions- antiport
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what is the amount of solute excreted equal to?
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the amount filtered minus the amount reabsorbed plus the amount secreted
F-R+S= excreted |
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filtration fraction
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one fifth of renal plama flow filters into the tubule lumen. The percentage of total plasma volume that filters is called the filtration fraction.
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what are the pressures of the hydrostatic pressures in the ,capillaries?
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hydrostatic pressure in glomerular capillaries averages 55mm Hg, favoring filtration. Opposing filtration are colloid osmotic pressure of 30mm Hg and hydrostatic capsule fluid pressure averaging 15 mm Hg. the net driving force is 10 mm Hg, favoring filtration.
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what is glomerular filtration rate?
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the amount of fluid that filters into bowmans capsule per unit time. Average GFR is 125ml/min or 180L/day
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where does most reabsorption take place?
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in the PCT
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what is the transport maximum?
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the transport rate of saturation
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true or false, peritubular capillaries reabsorb fluid along their entire length?
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true
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how does secretion enhance excretion?
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by removing solutes from the peritubular capillaries. K+, H+, and a variety of organic compounds are secreted.
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how is the secretion of a molecule slowed?
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by molecules that are competing for renal carriers.
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what two things is excretion rate dependent on?
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1. its filtered load
2. whether it is reabsorbed or secreted as it passes through the nephron. |
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what is clearance
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it is how many milliliters of plasma passing through the kidneys have been totally cleared of a solute given a period of time.
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what is the importance of mesangial cells?
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in the basal lamina of the glomerulus alter the size of the filtration slits formed by the interlacing fingers of the podocytes
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transcytosis
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the vesicular transport of macromolecules from one side of the cell to the other
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is the PCT permeable to water?
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yes
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Is the PCT permeable to Na+ and Cl- ions?
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yes
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is the PCT permeable to glucose?
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yes
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is the descending loop of henle permeable to water?
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yes
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is the descending loop of henle permeable to Na+ and Cl- ions ?
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no
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is the desceding loop of henle permeable to glucose?
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no
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is the ascending loop of henle permeable to water
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no
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is the ascending loop of henle permeable to Na+ and Cl- ions?
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yes
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is the ascending loop of henle permeable to glucose?
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no
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where does the Na+/K+/2Cl- symporter act?
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in the thick asceding loop of henle. the loop simultaneously reabsorbs one Na+ one K+ and two Cl- ions.
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what do the principle cells of the DCT and collecting duct reabsorb and secrete?
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reabsorb Na+
secrete K+ |
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during secondary active transport in the PCT, Na+ moves down its electrochemical gradient using what protein to pull in glucose?
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SGLT
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during secondary active transport, glucose diffuses out of the basolateral side of the cell using what protein?
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GLUT
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why is inulin considered a control?
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because it is neither absorbed nor secreted, it is 100% excreted.
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explain glucose clearance
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100% of glucose reabsorbed
no glucose excreted glucose clearance is 0ml/min |
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explain urea clearance
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50% of urea reabsorbed
50% of urea excreted urea clearance is 50ml/min when 100ml since urea clearance is less than that of inulin (100%), the urea has therefore been reabsorbed. |
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explain penicillin clearance
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filtered but not reabsorbed
additional penicillin molecules from plasma in peritubular capillaries penicillin clearance is 150ml/min which is greater than inulin clearance, and tehrefore penicillin is secreted. there is more penicillin excreted than was filtered. |
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how do you determine the filtered load?
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filtered load of X = [X]plasma x GFR
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what is the filtered load of inulin?
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=excretion rate of inulin
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how do you determine GFR
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GFR = excretion rate of inulin/[inulin]plasma = inulin clearance
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what is GFR also equal to?
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inulin clearance
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where do thiazides act?
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on the DCT
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what do spironalactone inhibit?
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aldosterone and is K+ sparing
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which hormone is very important in the formation of concentrated urine?
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ADH
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what are the three main solutes that contribute to high osmolarity?
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Na, Cl, and urea
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what are the two main factors that contribute to the osmotic gradient?
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1. differences in water and solute permeablity and reabsorption in the loop of henle and collecting duct.
2. the countercurrent flow in the two segments of the loop of henle. |
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what are the three components of the countercurrent mechanism?
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1.renal countercurrent multiplier
2.vasa recta removes water 3.urea increases osmolarity in the medullary interstitium |
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with maximal vasopressin, the collecting duct is freely permeable to water, true or false?
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true
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in the absence of vasopressin, the collecting duct is impermeable to water, true or false?
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true
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where does aldosterone and act?
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in the DCT collecting ducts, primary target is the principle cells.
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what is the primary stimuli for aldosterone?
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-potassium concentration (Na+ goes into the urine, K+ back to the plamsa)
-decreased blood pressure |
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what effect does AngII have on arterioles?
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vasoconstriction, increase in blood pressure
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what effect does AngII have on the cardiovascular control center in the medulla oblongata?
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increase in cardiovascular response, increase in blood pressure
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what effect does AngII have on the hypothalamus?
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increase in vasopressin, increase in thirst, inncrease in volume and maintainence of osmolarity, and increase in blood pressure.
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what effect does AngII have on the adrenal cortex?
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increase in aldosterone, increase in Na+ reabsorption, increase in volume and maintainence of osmolarity, and increase in blood pressure.
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why would the atrial natuiretic peptide become stimulated?
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increased blood volume, causes increased arterial stretch and release
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what effect does ANP have on the hypothalamus?
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less vasopressin, NaCl and H2O excretion
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what effect does ANP have on the kidneys?
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increased GFR, decreased renin, NaCl and H2O excretion
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what effect does ANP have on the adrenal cortex?
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less aldosterone, NaCl and H2O secretion.
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what effect does ANP have on the Medulla Oblongata?
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decreased blood pressure, NaCl and H2O secretion.
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filtrate leaving the ascending limb of the loop of henle is dilute. The final concentration of urine depends on ?
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the water permeability of the collecting duct.
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what controls collecting duct permeability to water in a graded fashion?
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the hypothalamic hormone vasopressin
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what two things will stimulate ADH production?
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an increase in ECF osmolarity and a decrease in blood pressure
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what is osmolarity monitored by?
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the hypothalamic osmoreceptors
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where are blood pressure and blood volume sensed by receptors?
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in the carotid and aortic bodies, and in the atria
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the countercurrent multiplier in the loop of henle creates a high osmolarity in the medullary interstitial fluid by actively transporting what out of the nephron?
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Na+, Cl-, and K+
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what is the function of the vasa recta?
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to carry away water leaving the nephron tubule so that water does not dilute the meduallary interstitum.
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what contributes to the high osmolarity in the renal medualla?
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urea
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what is the primary determinate of ECF volume?
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the total amount of Na+ in the body
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which hormone increases Na+ reabsorption and K+ secretion?
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aldsoterone
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where does aldosterone act
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the principle cells of the DCT
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what does aldosterone enhance?
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Na+ K+ ATPase activity and increases open time of Na+ and K= leak channels.
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what controls aldosterone secretion?
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the adrenal cortex
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does ECF K+ stimuate or inhibit aldosterone secretion?
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stimulates
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does an increase in osmolarity ECF stimulate or inhibit aldosterone secretion?
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inhibits
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true or false? the stimuli for the release of renin are related either directly or indirectly to low blood pressure?
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true
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what is the mechanism of ANP?
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enhances Na+ excretion and urinary water loss by increasing GFR, inhibiting tubular reabsorption of NaCl, and inhibiting the release of renin, aldosterone, and vasopressin.
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what hormones trigger salt appetite?
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aldosterone and angiotensin
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what is the law of mass balance?
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homeostatic compensations for changes in salt and water balance. Fluid and solute added to the body must be removed, and fluid and solute lost must be replaced.
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what does aldosterone do to K+
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kicks it out
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