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43 Cards in this Set
- Front
- Back
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What percent of cardiac output goes to Renal blood flow (RBF)
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20% (1.1L/min)
RBF regulation is targeted to maintaining filtration, not meeting metabolic needs. Delivery of oxygen far exceeds metabolic needs in the cortex of the kidney. |
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Where is the majority of RBF distributed in the context of the cortex vs. medulla?
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Cortex- to the renal corpuscles, 5 ml blood/g tissue, whereas brain gets .5ml/g tissue
Medulla- less blood but more metabolic activity- |
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Since inner medulla has less blood flood, what could this render it too?
Why is blood flow limited to medulla? |
more likely to get hypoxic
- limited so electrolyte balance can be maintained (very thin line between too little and too much) |
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What are the two crucial things that regulate RBF by controllling ease of blood to get to and through the glomerular capillaries?
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Afferent and efferent arterioles (controlled by innervations)
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Describe two important differences between glomerular capillary and systemic capillaries...
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1. The low resistance of the GC and the presence of the efferent arteriole lead to a very small drop in hydrostatic pressure.
2. 2. The pressures favor filtration throughout the length of the glomerular capillary. |
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Describe the main type of innervation on the afferent arteriole in RBF
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Sympathetic innervation is extensive.
- norepinephrine is released vasoconstriction via a1 and a2 receptors |
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What is GFR?
What is normal GFR? |
glomerular filtration rate- volume of plasma filtering into Bowman's space every minute
100-125 ml plasma/min (normal range) |
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Main renal vasoconstrictor neurotransmitters
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Norepinephrine
Angiotensin II Vasopressin (ADH) |
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What two numbers do you need to renal plasma flow?
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1. Renal Blood Flow
2. Hematocrit |
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Main renal dilator neurotransmitters
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1. Dopamine- also systemically given for BP control
2. Prostaglandin E2- becomes a major player in certain renal diseases therefore aspirin can be nephrotoxic under certain conditions. |
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Knowing RBF = 1.1, and Hct= .45 show how to calculate RPF...
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RPF = RBF x (1-Hct)
RPF = 1.1 L/min x (1 -.45) RPF = 1.1 L/min x 0.55 RPF = 0.60 L/min (600 mL/min) |
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With glomerular filtration describe the layers (general)
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1. Basement membrane
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Describe the FF (filtration fraction)
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Is the percent of renal plasma flow that is filtered (moves into Bowman’s space).
FF = GFR/RPF FF = [120 mL plasma/min]/[600 mL plasma/min] FF = 0.2 In other words, 20% of the plasma that enters the kidney will also enter Bowman’s space. |
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Glomerular filtration... describe the basement membrane
What specialization prevents glucose, Na, albumin, RBC, and WBCs from all getting through? |
In bowmann's space
- glucose, Na, albumin, RBCs, will cross but there are fenestration in the endothelium Fenestration: specialization does that not allow RBCs, and WBC from crossing |
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What is the tubular load?
Give formula... |
how much (in mg or g) of a substance enters the tubule each minute (dissolved in the plasma, of course…)
tubular load = GFR x [X]plasma |
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Describe podocytes and pedicels
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Part of specialization #2 in basement membrane: reduce surface area slightly
1. Podocytes (epithelial cells) 2. Pediccels (foot projections) |
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Constriction of the EFFERENT arteriole will ______ blood flow away the glomerular capillaries, _______ the amount of blood in the capillary, _______ the net filtration pressure, _______ GFR
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decreasej, increase, increase, INCREASING
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Describe the 3rd specialization of the basement membrane in glomerular filtration
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The basement membrane and the pedicels are lined with or contain ‘polyanionic substances’:
What this means: Larger negatively charged substances will not move across the filtration barrier, even though they might physically be able to get through the slit pore. |
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If both the afferent and efferent constrict:
RBF will ______? GFR may _____? |
decrease
stay the same |
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Name the three specializations in glomerular filtration...
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1. Fenestrated capillary endothelium
2. epithelial cells (podocytes) pedicels (foot projections) 3. polyanionic substances on pedicels and basement membranes |
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What will increase in pieGC (dehydration) lead to in GFR?
What will increase in pieBS usually associated with filtration of proteins like albumin do? |
1. decrease
2. increase GFR favors filtration |
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What is the plasma concentration of Na, K, Cl, Glucose compared to Bowman's Space?
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same
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Describe the mechanisms by name that regulate the GFR...
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1. Myogenic response
2. Tubuloglomerular feedback |
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What are the four freely filtered main particles?
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1. Na
2. K 3. Cl 4. Glucose |
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What is the formula for the volume filtered?
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Hydraulic permeability x SA x Net filtration pressure
Net filtration- hydrostatic/oncotic (=osmotic) SA= surface area- related to # glomeruli (renal corpuscles) Hydraulic permeability = how easy it is for water to move through the filtering membrane (usually a constant) |
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How do you usually define Hydraulic permeability and surface area?
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Kf
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Net filtration pressure components:
1. Hydrostatic pressure 2. Oncotic (=osmotic) pressure |
1. Hydrostatic pressure
- glomerular – favors filtration (PG) - Bowman’s space – opposes filtration (PBS) 2. Oncotic (=osmotic) pressure (pie) - glomerular – opposes filtration (pieG) -Bowman’s space – favors filtration (pieBS) |
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Of the hydrostatic and oncotic components of net filtration pressure which go together?
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1. glomerular/Bowmans space (Pg and pieBS)
2. bowmans space/ glomerular )Pbs, pieG |
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What is the glomerular filtration equation for volume filtered?
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Volume filtered = Kf [(PGC + pieBS) – (PBS + pieGC)]
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Kidney always favor filtration or absorption?
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filtration
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What is hematocrit and how is it measures?
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% of blood that is cells = hematocrit
norms 35 - 45% - women ~ 40 - 50% - men |
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What is formula to calculate renal plasma flow (RPF)?
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% of blood that is plasma = 1 - hematocrit
If a patient’s hematocrit is 45%, then (1 - .45) or .55 (55%) of the blood is plasma… |
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Why is the number of Tubular load important?
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This number is important because it tells us how much of a substance the PCT and DCT/CD are going to ‘have’ to deal with…
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Taking glucose as an example, in a normal person, the [glucose]plasma may be 95 mg/dL (= 0.95 mg/mL plasma). GFR is 110 mL plasma/min…
Calculate Tubular load |
Tubular load = GFR x [X]plasma
Tubular load = 110 mL plasma/min x 0.95 mg/mL plasma Tubular load = 104.5 mg glucose/min or 0.10 g glucose/min |
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How is the GFR regulated?
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Changed or controlled by altering any factors in formula, some are physiological and pathological
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What does a passive increase in the renal artery pressure do to the GFR?
What does a passive decrease in renel artery pressure do to GFR? |
1. increase unless countered
2. decrease GFR |
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What does constriction of the afferent arteriole do to blood flow into glomerular capillaries and net filtration pressure?
Also GFR? |
decrease blood flow to glomerular capillaries
decrease net filtration pressure reducing GFR |
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Dilation of the afferent arteriole will _____ blood flow into the glomerular capillaries and _____ the net filtration pressure, _____ GFR
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increase,increase, increasing
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Hydrostatic pressure in the glomerular capillary can be altered by changing the ______ arteriole
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efferent
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Dilation of the efferent arteriole will ______ blood flow away the glomerular capillaries, _______ the amount of blood in the capillary, ______ the net filtration pressure, ________ GFR
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increase, decrease, DEcrease, DECREASING
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What causes increase in PBs?
Result? |
An increase in PBS (hydrostatic pressure in bowmans space) can result from anything that prevents the tubular fluid from leaving the nephron (kidney stone)… This causes the fluid to back-up in the nephron
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Describe the myogenic response and role in GFR regulation...
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Increased arterial pressure
Increased stretch of the arterioles in the kidney elicits contraction of the vascular smooth muscle the constriction of the vessels leading to the glomerular capillary reduces the pressure in the glomerular capillary bed. |
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Describe the second mechanism of GFR regulation....
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Tubuloglomerular feedback
Requires the JGA -Increased arterial pressure - Increased GFR - Increases the tubular load of sodium - More sodium arrives at the macula densa (Macula densa cells are sodium sensing) - causes release of vasoconstrictor that will act on afferent arteriole (dont know why) - reduces the blood pressure in the glomerular capillary |
