RENAL 03 - Filtration and blood flow

Question 1

What is the glomerular filtration barrier composed of (3)

Answer 1

Fenestrated capillary epithelium
fused basement membrane with negative charge barrier
podocyte foot processes (slit diaphragm)

Question 2

Kidneys are activated by what branch of ANS, (and what branch does not affect kidneys)

Answer 2

SNS (PSNS does not affect them)

Question 3

Majority of SNS innervation is on which arterioles set?

Answer 3

Afferent

Question 4

Purpose of fenestrated epithelium

Answer 4

allow substances to pass through endothelial cells

Question 5

purpose of basement membrane

Answer 5

negative charge helps with selectivity of what can go through -repels proteins

Question 6

purpose of podocyte foot processes / slit diaphragm

Answer 6

processes can expand and contract out, helps by acting as filtration barrier against macromolecules

Question 7

Why doesn’t albumin get into the tubular system?

Answer 7

it’s small, so it gets through the fenestrate, but it is repelled by the basement membrane’s negative charge

Question 8

How does molecular weight impact filtration

Answer 8

the larger the molecule it is filtered less

Question 9

how does electrical charge impact filtration

Answer 9

negatively charged molecules are filtered less, but positively charged molecules are filtered more (and even more filtered than neutral molecules)

Question 10

Properties of inulin and filtration

Answer 10

although inulin is very complex, its overall molecular weight is low, so it is freely filtered, and it lacks a charge that is repelled by basement membrane so it gets through.

Question 11

How much of the RPF passes through into the bowman’s space?

Answer 11

20%

Question 12

Does glucose go through the glomerular filtration barrier?

Answer 12

Yes

Question 13

Do large proteins go through glomerular filtration barrier?

Answer 13

No

Question 14

What are direct determinants of glomerular filtration rate?

Answer 14

Starling forces (permeability, hydrostatic pressure, oncotic pressure, put together being the Net Filtration Pressure)

Question 15

Compared to skeletal capillaries, the Kf of glomerular capillaries is (higher or lower)

Answer 15

higher because of the fenestrations (windows)

Question 16

Blood flow to kidneys can be determined by what equation?

Answer 16

Q=deltaP/R

Question 17

Kidneys have a vascular system in ___(series/parallel)__. What does this mean about the overall resistance?

Answer 17

Parallel; this means total resistance is quite low

Question 18

Mean pressure in glomerular capillaries is ____(high/low)___ compared to skeletal capillaries?

Answer 18

High

Question 19

What happens to oncotic pressure along the length of the glomerular capillary? Why?

Answer 19

It becomes higher. This is because you’re filtering out the fluid, so you’re concentrating the protein there (more protein per unit volume)

Question 20

Hydrostatic pressure in glomerulus vs skeletal muscle interstitium?

Answer 20

It’s higher, but still much lower than the hydrostatic pressure in the glomerular capillary

Question 21

Hydrostatic pressure in the glomerular capillary?

Answer 21

High throughout the length of the capillary and much higher than what you would find in skeletal muscle capillaries due to the fact that it is between two arterioles

Question 22

Oncotic pressure in bowman’s space

Answer 22

near zero

Question 23

Aside from just “fenestrations” what can be attributed to high amount of filtration going on in the glomerulus?

Answer 23

high surface area of openings in capillaries overall leading to a high amount of fluid coming out

Question 24

What would the effect of renal arterial pressure increasing be on GFR?

Answer 24

This would increase GFR due to an increase in hydrostatic pressure

Question 25

What would the effect of relaxation of glomerular mesangial cells be on the GFR?

Answer 25

This would increase glomerular surface area (increase in permeability) and as a result you increase filtration (increase in GFR)

Question 26

What would the result of an intratubular pressure increase (ex. obstruction of a tubule, extrarenal urinary system obstruction) be on GFR?

Answer 26

This will DECREASE the GFR. This is because you would be increasing the hydrostatic pressure in the bowman's space, which would oppose filtration

Question 27

What would the effect of an increase in systemic oncotic pressure be on the GFR?

Answer 27

This will decrease filtration rate (decrease GFR)

Question 28

What would a decreased RBF do to the GFR?

Answer 28

This will decrease GFR, partly due to an increase in the oncotic pressure along the glomerular capillaries (it becomes concentrated)

Question 29

What would the effect of afferent arteriole dilation be on GFR?

Answer 29

This will increase GFR ; this is decreasing afferent arteriolar resistance and increasing flow to the area, therefore, the pressure is increasing.

Question 30

What would the effect of constricting the efferent arteriole be on GFR?

Answer 30

This will increase GFR because you're increasing resistance to flow on the exit side

Question 31

If you have a decrease in effective circulating volume, what is the effect on GFR? What is a situation in which this might happen?

Answer 31

This would result in a decrease in GFR. This would happen in, for instance, heart failure or hemorrhage.

Question 32

If you hve an immune complex on the glomerulus, what is the result of GFR?

Answer 32

This is going to lead to inflammation of the glomerulus which decreases overall glomerular filtration rate; however you also get holes in the capillaries so what DOES get through can be quite large and include RBC's, WBC's, and proteins

Question 33

What is the result of kidney stones on glomerular filtration rate?

Answer 33

This would lead to a backup of pressure that eventually increases bowman's space hydrostatic pressure and decreases the overall glomerular filtration rate

Question 34

how do we calculate blood flow

Answer 34

Flow is equal to the pressure gradient of two locations over the resistance of the system

Question 35

Where does the majority of blood flow go in the kidney

Answer 35

Cortex

Question 36

Where is the vast MINORITY of vascularization in the kidney

Answer 36

inner medulla ; you really only have vasa recta here along the juxtamedullary nephrons

Question 37

Where is the largest pressure drop in the kidney vascular pressure?

Answer 37

Think about the highest resistance vessels (just like what Jonathan taught us, it's the arterioles, both afferent and efferent)

Question 38

Where is oncotic pressure highest in the kidneys

Answer 38

Efferent arterioles (we concentrated protein in the glomerular capillaries and in the peritubular capillaries we're going to dilute it back down when we save water)

Question 39

Constriction of afferent arteriole leads to what affect of renal blood flow and what affect on GFR

Answer 39

Decrease RBF, decrease GFR (due to decrease in hydrostatic pressure in glomerular capillaries)

Question 40

Constrition of EFFERENT arteriole leads to what affect on renal blood flow and what affect on GFR

Answer 40

This leads to a DECREASE in renal blood flow (resistance increases in the exit portion) but an INCREASE in GFR due to an increase in hydrostatic pressure along the glomerular capillary

Question 41

Dilation of the efferent arteriole leads to what affect on renal blood flow and GFR

Answer 41

This will increase RBF and decrease GFR due to a decrease in hydrostatic pressure within the glomerular capillaries

Question 42

What is the effect of dilation of the afferent arteriole on renal blood flow and GFR?

Answer 42

This is going to lead to an increase in renal blood flow and in increase in GFR due to an increase in glomerular capillary hydrostatic pressure

Question 43

GFR and RBF can be maintained over..... what range of pressures?

Answer 43

A broad range of pressures (100-180mmHg) Therefore if you increase arterial blood pressure, you don't necessarily increase RBF and GFR

Question 44

At what arterial blood pressure do kidneys begin to shut down?

Answer 44

70mmHg

Question 45

Intrinsic regulation of GFR and RBF

Answer 45

vasoconstricting and vasodilating factors, myogenic response, tubuloglomerular feedback from vasa recta

Question 46

Extrinsic regulation of GFR and RBF

Answer 46

Sympathetic nervous system, bloodborne or endogenous sybstances (ex. angiotensin II), stress factors such as hemorrhage