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dxtxpx Forum Guru Topics: 259 Posts: 1233	Feb 09, 2004 - 10:38 AM       #1 When arterial BP of an individual changes from 100 mmHg to 150 mmHg, GFR a) remains unchanged b) increases by 10% c) increases by 50% d) decreases by 25% e) decreases by 50%
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peekay Forum Guru Topics: 102 Posts: 587	Feb 09, 2004 - 3:18 PM       #2 remains unchanged
Topics: Posts:	Feb 09, 2004 - 8:06 PM       #3 increases by 50 [percent cause the hydostatic pressure in the glomerular capilllary increases which is the main factor .. not 10 but 50 percent cause because slight changes in pressure cause huge changes in gfr
mjl1717 Forum Junior Topics: 964 Posts: 5442	Feb 09, 2004 - 8:12 PM       #4 I like that reasoning and i think that logic would enhance or precipatate glomerulosclerosis
asmi Forum Hero Topics: 1049 Posts: 4620	Feb 09, 2004 - 8:39 PM       #5 yes i too agree with C since increase in angiotensin II(constricts efferent arterioles)---> decrease in RPF---> increase in GFR.
dxtxpx Forum Guru Topics: 259 Posts: 1233	Feb 10, 2004 - 5:44 AM       #6 Peekay is correct choice a) remains unchanged Filtration of blood across glomerular basement membrane depends on difference between glomerullar capillary hydrostatic pressure (45 mmHg) and the sum of Bowman's capsule hydrostatic pressure (10 mmHg) and the plasma protein osmotic pressure (28 mmHg). Thus, the net pressure supporting glomerular filtration is 7 mmHg. Due to extreme porosity of fenestrated glomerular capillaries and the gaps between foot processes of podocytes, approx 180 L/day of glomerular filtrate is produced. GFR can easily be calculated as 125 mL/min. This rate is relatively invariant, even with large changes in BP. A substantial increae in BP will result in concomitant decrease in blood flow thru afferent arteriole due to smooth muscle contraction. Also, macula densa in distal convulated tubule detects changes in rate of production of glomerular filtrate and feeds back on afferent arteriole to autoregulate GFR Stimulation of sympathetic nerve fibers to kidney causes vasoconstriction in afferent arteriole, leading to decreae in GFR. Factors that vasoconstrict efferent arterioles will increase GFR. Conversely, a decrease in vascular tone will result in an increase in GFR. Catecholamines are also potent vasoconstrictirs of afferent arterioles and will therefore cause a significant decrease in GFR

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