Physiology - Glomerular Filtration and Renal Blood Flow

Question 1

which has a larger diameter - the afferent or efferent arteriole?

Answer 1

afferent

Question 2

what are the three barriers to filtration?

Answer 2

glomerular capillary endothelium
basement membrane
slit processes of podocytes

Question 3

what is the glomerular capillary endothelium a barrier to?

Answer 3

red blood cells

Question 4

what is the basement membrane a barrier to?

Answer 4

plasma proteins

Question 5

what are podocytes a barrier to?

Answer 5

plasma proteins

Question 6

what is another name for the basement membrane?

Answer 6

the basal lamina

Question 7

what is the basement membrane made of?

Answer 7

collagen
glycoproteins

it is acellular

Question 8

how does the basement membrane form a barrier ti plasma proteins?

Answer 8

it confers a net negative charge, stopping the positively charged proteins passing through

Question 9

does glomerular filtration require energy?

Answer 9

no - it is completely passive

Question 10

what two pressures favour filtration in the glomerular capillary?

Answer 10

glomerular capillary blood pressure

bowman’s capsule oncotic pressure

Question 11

what two pressures oppose filtration in the glomerular capillary?

Answer 11

bowman’s capsule hydrostatic pressure

capillary oncotic pressure

Question 12

what is the normal net filtration pressure in the glomerular capillary?

Answer 12

10 mmHg

overall, filtration is favoured

Question 13

what is the normal value for bowman’s capsule oncotic pressure and why?

Answer 13

zero

there are no plasma proteins in the bowman’s capsule to create the pressure

Question 14

what is another name for oncotic pressures?

Answer 14

colloid osmotic pressures

Question 15

what is GFR?

Answer 15

the rate at which plasma is filtered from the glomeruli into the bowman’s capsule per unit time

Question 16

how do you calculate GFR?

Answer 16

Kf x net filtration pressure

Question 17

what is Kf?

Answer 17

the filtration coefficient

a measure of how permeable the membrane is

Question 18

what is the normal value for GFR?

Answer 18

125 ml/min

Question 19

what is the extrinsic regulation of GFR?

Answer 19

sympathetic control via the baroreceptor reflex

Question 20

what effect does increased blood pressure have on GFR regulated by baroreceptors?

Answer 20

increased capillary blood pressure, increased filtration pressure, increased GFR

Question 21

what is another name for intrinsic regulation of GFR?

Answer 21

autoregulation

Question 22

what are the two mechanisms for autoregulation of GFR?

Answer 22

myogenic mechanism

tubuloglomerular feedback mechanism

Question 23

how does the myogenic mechanism control GFR?

Answer 23

if vascular smooth muscle is stretched by increased blood pressure, it automatically contracts

this regulates the blood flow to the glomerular kidney

Question 24

what type of feedback loop is the tubuloglomerular feedback mechanism?

Answer 24

negative feedback

Question 25

how does the tubuloglomerular feedback mechanism control GFR?

Answer 25

if GFR rises, more NaCl flows through the tubules and the macula densa releases vasoconstrictive mediators this causes constriction fo afferent arterioles and a decrease in GFR

Question 26

what is BPGC?

Answer 26

the glomerular capillary blood pressure promotes filtration

Question 27

what is COPGC?

Answer 27

capillary oncotic pressure opposes filtration

Question 28

what is HPBC?

Answer 28

bowman's capsule hydrostatic pressure opposes filtration

Question 29

what is COPBC?

Answer 29

bowman's capsule oncotic pressure promotes filtration

Question 30

what could increase the HPBC and what effect does this have on GFR?

Answer 30

kidney stones reduces GFR

Question 31

what could increase the COPGC and what effect does this have on GFR?

Answer 31

diarrhoea reduces GFR

Question 32

what could decrease the COPGC and what effect does this have on GFR?

Answer 32

severe burns increases GFR

Question 33

what effect does decreased Kf have on GFR and what could cause this?

Answer 33

decreased GFR a change in the surface area available for filtration

Question 34

what is plasma clearance a measure of?

Answer 34

how effectively the kidneys can clean the blood of a substance

Question 35

what is plasma clearance and what are its units?

Answer 35

the volume of plasma completely cleared of a substance per minute ml/min

Question 36

what is the plasma clearance of inulin?

Answer 36

the same as GFR

Question 37

why is no glucose normally found in the urine?

Answer 37

it is freely filtered and then completely reabsorbed, so none is secreted

Question 38

what is the plasma clearance value for glucose?

Answer 38

zero

Question 39

compared to GFR, what is the plasma clearance for urea?

Answer 39

less than GFR

Question 40

what happens to urea in the nephron?

Answer 40

filtered partly reabsorbed not secreted

Question 41

what happens to hydrogen in the nephron?

Answer 41

filtered secreted not reabsorbed

Question 42

compared to the GFR, what is the clearance of hydrogen?

Answer 42

greater than GFR

Question 43

what does PAH stand for and what is it?

Answer 43

para-amino hippuric acid an exogenous organic anion

Question 44

what is PAH used for?

Answer 44

calculating renal plasma flow (RPF)

Question 45

what is the filtration fraction?

Answer 45

the fraction of plasma flowing through the glomeruli that is filtered into the tubules

Question 46

how do you calculate the filtration fraction?

Answer 46

GFR/renal plasma flow

Question 47

what is the filtration fraction in a healthy adult?

Answer 47

20% means that 20% of the plasma that enters the glomeruli is filtered