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ZOO 3115; Dr. Cherrington, Kidney (04-24)
Study material for UW ZOO 3115 Exam 3
32
Physiology
Undergraduate 3
05/03/2015

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Term
(04-24) What do mesangial cells do?
Definition
support and regulate blood flow in glomerular capilaries
Term
(04-24) What kidney cell/s have fenestrations?
Definition
Capillary endothelial cells (podocytes have "slit pores")
Term
(04-24) What other type of muscle does a mesangial cell resemble? Why?
Definition
It is reminiscent of smooth muscles; it is capable of contracting.
Term
(04-24) How many layers of what kind of membrane must filtrate pass through? What are the layers' names?
Definition
filtrate must pass trough 3 layers of glomerular membrane: Capillary endothelial cell, basement membrane, epithelial cells
Term
(04-24) How much plasma moves into the filtrate?
Definition
20.00000%
Term
(04-24) Define glomerular filtration rate (GFR).
Definition
The amount of plasma filtered per unit time
Term
(04-24) From the glomerulus, where does filtrate go?
Definition
Bowman's space
Term
(04-24) We filter more than 6 L of plasma through our body every hour. Why don't we have to pee constantly?
Definition
reabsorption happens!
Term
(04-24) Define glomerular filtration pressure (GFP). What is used to calculate it?
Definition
GFP is the driving force for filtration. It is the sum of the "Starling forces"
Term
(04-24) What are the factors in GFP that favor movement from blood to filtrate?
Definition
1) PGC = hydrostatic pressure in the glomerular capillaries (mean arterial pressure matters here); 2) (Pi)BC = Bowman's capsule osmotic pressure
Term
(04-24) How effective is the capsule osmotic pressure in the movement from blood to filtrate?
Definition
It's not. Not really. We can assume the value is zero.
Term
(04-24) What are the factors of glomerular filtration pressure that influence movement from filtrate back to blood?
Definition
1) (Pi)GC = the osmotic pressure in glomerular capillaries (affected by protiens like albumin and globulins) 2) PBC = the hydrostatic pressure in Bowman's capsule
Term
(04-24) What is the formula for glomerular filtration pressure? (given on an exam)
Definition
GFP = PGC + (Pi)BC - PBC - (Pi)GC
Term
(04-24) What is the main driving force (factor with the highest value) in glomerlar filtration pressure?
Definition
Hydrostatic pressure in the glomerular capillaries (PGC)
Term
(04-24) GFR is CONSTANT/VARIABLE across a range of blood pressures.
Definition
CONSTANT
Term
(04-24) What types of control influence Glomerular filtration rate?
Definition
1) Local , or intrinsic, control 2) Zone of autoregulation.
Term
(04-24) Define zone of autoreglation.
Definition
An area on a GFR graph between ~70 and ~180 that keeps GFR constant.
Term
(04-24) what are the three mechanisms of inrinsic control within the zone of autoregulation?
Definition
1) Myogenic regulation (smooth muscle of the afferent arteriole) 2) Tubuloglomerular feedback (macula densa senses fluid flow and contracts afferent arteriole) 3) Mesangial cell contraction (contract in response to stretching)
Term
(04-24) In myogenic regulation of GFR, what are the physical changes made when there is an increase in pressure?
Definition
the afferent arteriole contracts, increasing resistance and decreasing glomerular filtration rate
Term
(04-24) What physiological structures does tubuloglomerular feedback affect?
Definition
cells of the macula densa in the distal tubule
Term
(04-24) In tubuloglomerular feedback, what reacts to an increase in fluid flow?
Definition
The macula densa cells sense increases in fluid flow in the distal tubule. An increase in flow leads to a contraction of the afferent arteriole and a decrease in Glomerular Filtration Rate.
Term
(04-24) What do mesangial cells do to help keep GFR lower?
Definition
An increases blood presure sretches mesangial cells, which contract. This leads to decreased filtration surface and a decrease in glomerular filtration rate.
Term
(04-24) Outside the zone of autoregulation, how is GFR controlled? What is the control dependent on?
Definition
Extrinsic control of GFR (You can think of this as "non-local"). It has to do with the baroreceptor reflex.
Term
(04-24) What's the formula for mean arterial pressure?
Definition
MAP = CO x TPR
Term
(04-24) What does the extrinsic control of GFR do when it senses a large amount of blood loss?
Definition
It increases cardiac output and total periferal resistance, lowering GFR
Term
(04-24) Define filtered load. What is its one caveat?
Definition
How much of a particular solute is filtered per unit. Caveat: the solute must freely cross the glomerular membrane
Term
(04-24) What is the formula for the filtered load (FL)?
Definition
FL = (glomerular filtration rate) ([concentration X in plasma])
Term
(04-24) If you have a filtered load of 125 mL/min, and you're measuring glucose at 1 mg/mL, what is the FL of glucose?
Definition
FL of glucose = (125 mL/min) (1 mg/mL) = 125 mg/min
Term
(04-24) Define clearance, in terms of GFR
Definition
The volume of plasma cleared of a substance per unit time
Term
(04-24) What is the volume for clearance?
Definition
Clearance = ((concentration of X in urine)(rate of urine production))/(concentration of X in plasma) AKA Cx = (([X]urine])(dU/dt))/([X]plasma)
Term
(04-24) Why is the clearance of glucose zero -- even when the filtered load of glucose is greater than zero?
Definition
Clearance indicates a volume of plasma that is completely cleared of a substace. Glucose is freely filtered and completely reabsorbed, so the concentration of [glucose]urine will always be 0 (in the numerator on the clearance formula
Term
(04-24) What is the rule about clearance about a freely filtered, not secreted nor reabsorbed substance?
Definition
If a substance x is freely filtered and is not secreted or reabsorbed, then clearance of that substance equals GFR
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