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Glomerular Filtration II
Glomerular Filtration II
13
Medical
Graduate
04/12/2011

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Term
In what arterial pressure range are both GFR and RBF maintained?
Definition
80-180 mm Hg
Term
What are two intrinsic mechanisms of autoregulation?
Definition
Myogenic mechanism
Tubuloglomerular feedback
Term
Define myogenic mechanism?
Definition
the changes in pressure in the arterioles causes the smooth muscles to stretch which stimulates them to contract.
Term
What is the receptor and stimulus of the tubuloglomerular feedback mechanism?
Definition
The receptor is the macula densa.
The stimulus is an increase in NaCl delivery to the macula densa or an increase in tubular fluid flow rate. Either of these cause a fall in GFR.
Term
What are the requirements of a substance being used to measure glomerular filtration rate?
Definition
-must pass freely from glomerular capillaries into filtrate
-must be neutrally charges
-must not bind to plasma proteins
-must not be secreted
-must not be reabsorbed
-all that is filtered must be secreted
Term
What substance is used to glomerular filtration rate?
Definition
Inulin is infused IV to measure GFR.
Term
Define renal clearance.
Definition
The volume of plasma from which all of a substance has been removed and excreted into urine per unit of time.
Term
T/F. Inulin clearance is dependent on plasma inulin concentration and urine flow.
Definition
False. Inulin clearance is independent of plasma inulin concentration and urine flow.
Term
What endogenous substance approximates GFR?
Definition
Creatine.
Term
What can creatine be an approximation of?
Definition
Plasma creatine levels can be an approximation of GFR
Term
If the amount of inulin filtered into the tubule does not change then what would changes in concentration of inulin reflect?
Definition
Changes in water movement.
Term
What is fractional excretion?
Definition
Fractional excretion shows the fraction of the filtered mass of a substance that was excreted.
Term
How is fractional excretion found?
Definition
Mass excreted divided by mass filtered
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