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Glomerular Filtration

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imissyou419's version from 2017-03-29 13:45

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Question Answer
_________% of all the blood that travel through the glomerulus is filtered into capsular space20 (80% leave glomerulus and cycle back to body and come back later)
Filtering too much fluid into caspular spacefluid flows too fast through tubule so inability for tubule cells to properly balance the filtrate;
chronic high BP causes more fluid to filter, rupturing glomerular capillaries (get scarring of nephron, apoptosis) so lose # of nephrons;
net filtration > 10 mmHg results in GFR > 180 L/day
Filtering too little fluid into caspualr spacebuild up of waste products; net filtration <10 mmHg result in GFR < 180L/day
Normal glomerular filtration rate (GFR)125 ml/min (180L/day), mostly due to the net filtration pressures in renal corpuscle (4 forces) but surface area available for filtration and permeability of barriers contribute too
Hydrostatic pressure of glomerular capillaries (PGC)pressure created due to the presence and movement of fluid (blood) through the glomerular capillaries; contribute most to filtration; affected by diameters of afferent and efferent arterioles
Hydrostatic pressure of Bowman's capsule (PBC)pressure created due to the presence of fluid (filtrate) in Bowman's space, negative value because against filtration
Colloid osmotic pressure of glomerular capillaries (piGC)pressure created due to the presence of proteins in the fluid (blood) in the glomerular capillaries
Colloid osmotic pressure of Bowman's capsule (piBC)pressure created due to the presence of proteins in the fluid (filtrate) in Bowman's space; proteins draw water to themselves so good for filtration but bad because proteins should not be there!!!
Increasing space between podocytes contributing to GFRIncreasing GFR
Increasing the permeability of basal laminaIncrease GFR (when you start filtering proteins also increase GFR)
Decreasing the size of glomerular poresDecrease GFR
Afferent arteriole constrictedDecrease GFR (blood flow & pressure lower in glomerulus after constriction)
Efferent arteriole constrictedIncrease GFR (pressure in glomerulus increased before constriction)
Both arterioles constrictedDecrease GFR b/c afferent arteriole has greater effect
Autoregulation of GFRmaintains a constant GFR when MAP = 80-180 mmHg by changing diameters of afferent and efferent arteriole; due to 2 autoregulatory mechanisms
Myogenic response high BPafferent arteriole stretches,
stretch sensitive cation channels open,
smooth muscle cells in the afferent arteriole depolarize,
VG-Ca2+ channels open in smooth muscle,
smooth muscle contracts (afferent arteriole constricts),
BP and blood flow decreases in the glomerulus
Tubuloglomerular Feedback response to high BPWhen GFR increases due to high BP,
more water and ions are filtered into caspular space, faster flow and accomulation of ions by macula densa cells,
macula densa cells detect rise in NaCl and release ATP which is cleaved extracellularly to adenosine which causes VASOCONSTRICTION of the afferent arteriole, reducing GFR
Tubuloglomerular Feedback response to low blood pressureWhen GFR decreases due to low BP,
macula densa cells release NO causing vasodilation of afferent arteriole, increasing GFR
Adenosine in rest of the body is avasodilator (more blood goes to muscles that are more active), afferent arteriole express a1 receptor and cause vasoconstriction
Equation for excretionexcretion = filtration (GFR) - reabsorption + secretion
What substance should be used to measure GFR?measure creatinine in excretion (not reabsorbed or secreted)
GFR equationExcretion = GFR = [(creatinine]urine x urine volume) / [creatinine]plasma
Filtered load equation[X]plasma x GFR
memorize

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