Session 3 - Glomerular Filtration

Question 1

what are the 2 different types of nephrons

Answer 1

• cortical

- juxtamedullary

Question 2

describe cortical nephrons

Answer 2

shorter loop of henle which only just penetrates medulla

covered by peritubular capillaries

Question 3

describe juxtamedullary nephrons

Answer 3

longer loop of henle penetrating deep into the medulla

has peritubular capillaries and vasa recta

Question 4

what is the vasa recta

Answer 4

straight blood vessels running parallel to the loop of henle in juxtamedullary nephrons

Question 5

which type of nephron has sympathetic innervation

Answer 5

cortical

Question 6

which type of nephron has a high renin concentration

Answer 6

cortical

Question 7

what makes filtration selective

Answer 7

the filtration barrier

Question 8

what makes up the filtration barrier in the glomerulus

Answer 8

• capillary endothelium
• basement membrane
• podocytes

Question 9

how do particles filter through the capillary endothelium in the glomerulus

Answer 9

only small particles can pass through the fenestrations in the capillary walls

Question 10

how does the basement membrane stop some particles from being filtered in the glomerulus

Answer 10

the basement membrane is made up of glycoproteins, making it negatively charged, therefore it will repel negatively charged substances (including proteins)

Question 11

how do substances filter through podocytes in the glomerulus

Answer 11

they must be small enough to pass through the filtration slits set up by the projections of the podocytes

Question 12

true or false: negatively charged ions filter through the glomerulus easier than positively charged ions

Answer 12

false - negatively charged substances are repelled by the basement membrane, whereas positively charged substances are attracted

Question 13

what % of blood flowing through the afferent arteriole is filtered though the nephron

Answer 13

20%

Question 14

where abouts in the kidney is the nephron found

Answer 14

in the cortex

Question 15

what are the 3 pressures affecting filtration in the glomerulus

Answer 15

1. hydrostatic pressure of the glomerulus
2. hydrostatic pressure of the capsule
3. oncotic pressure in the glomerulus

Question 16

how is the hydrostatic pressure in the glomerulus produced

Answer 16

through cardiovascular output

also as the efferent arteriole is smaller than the afferent arteriole this creates a pressure difference

Question 17

how is the oncotic pressure in the glomerulus set up

Answer 17

as proteins can’t filter through, they are stuck in the glomerulus and so draw water across and back into the glomerulus

Question 18

what is the net pressure for fluid movement

Answer 18

10 mm out of the glomerulus

Question 19

what are the 4 mechanisms for autoregulation

Answer 19

• myogenic
• tubuloglomerular feedback
• tubuloglomerular balence
• sympathetic NS

Question 20

what detect changes in pressure in myogenic regulation

Answer 20

stretch receptors in the smooth muscle of the blood vessels

Question 21

what is the myogenic regulation to an increase in pressure/GFR

Answer 21

they cause the constriction of the afferent arteriole, limiting the amount of fluid entering the glomerulus, so less is filtering, lowering the GFR

Question 22

what is the myogenic regulation to an decrease in pressure/GFR

Answer 22

they cause dilation of the afferent arteriole, increasing the amount of fluid entering the glomerulus, so more is being filtered, increasing the GFR

Question 23

how would happen if both the afferent and efferent articles dilated

Answer 23

there would be no GFR, as this takes away the pressure difference between the AA and AE, so blood would flow straight through, without being filtered

Question 24

what cells detect pressure change in tubuloglomerular feedback

Answer 24

macula densa cells in the DCT

Question 25

how do the macula densa cells detect a change in GFR/pressure

Answer 25

by detecting a change in sodium chloride levels

Question 26

if sodium chloride levels had increased in the DCT what does that mean happened to the GFR/pressure

Answer 26

it had increased to give an increased in chloride

Question 27

what transporters allow the macula densa cells to detect an include in sodium chloride levels

Answer 27

NaKCC co-transporters on the apical membrane

Question 28

what happens in the tubuloglomerular feedback mechanism if a high GFR/pressure is detected

Answer 28

adenosine is released from the juxtaglomerular apparatus

Question 29

how does adenosine work to combat a high GFR

Answer 29

it bind to A1 receptors on the afferent arteriole to constrict it and binds to A2 receptors on the efferent arteriole to dilate it

Question 30

what happens in the tubuloglomerular feedback mechanism if a low GFR is detected

Answer 30

prostaglandins are released from the juxtaglomerular apparatus to cause dilation of the afferent arteriole

Question 31

when is the sympathetic NS involved in auto regulation

Answer 31

during haemorrhage, to constrict blood vessels and reduce blood loss

Question 32

what is the order of vessels blood flows in the kidneys

Answer 32

renal artery > segmental artery > interlobar artery > arcuate artery > interlobular artery > afferent arteriole

Question 33

what is the order of vessels blood flows in the kidneys

Answer 33

renal artery > segmental artery > interlobar artery > arcuate artery > interlobular artery > afferent arteriole