Lecture 33 Unit 5

Question 1

what is the formula for rate of excretion

Answer 1

rate of glomerular filtration+rate of secretion - rate of reabsorption

Question 2

what produces glomerular filtrate

Answer 2

blood pressure

Question 3

how much filtrate is reabsorbed per day to form how much urine per day

Answer 3

180 liters/day of filtrate to form 1-2 liters/day of urine

Question 4

what is filtering capacity enhanced by

Answer 4

• thinness of membrane
• large surface area of glomerular capillaries
• high glomerular capillary blood pressure

Question 5

what does the filtration barrier consist of

Answer 5

• fenestration of glomerular endothelial cell
• basal lamina of glomerulus
• slit membrane between pedicels

Question 6

what do fenestrations of glomerular epithelial cells do

Answer 6

prevents filtration of blood cells but allows all components of blood plasma to pass through

Question 7

what does the basal lamina of glomerulus do

Answer 7

prevents filtration of larger proteins

Question 8

what does the slit membrane between pedicels do

Answer 8

prevents filtration of medium sized proteins

Question 9

what are macula densa cells and where are they located

Answer 9

top of ascending limb and they interact with cells lining the afferent arteriole

Question 10

what is the thickened part of the ascending limb

Answer 10

macula densa

Question 11

what is the net filtration pressure in the nephron

Answer 11

10 mmHg

Question 12

what is the glomerular blood hydrostatic pressure

Answer 12

55 mmHg

Question 13

what is the capsular hydrostatic pressure

Answer 13

15 mmHg

Question 14

what is the blood colloid osmotic pressure

Answer 14

30 mmHg

Question 15

what is the amount of filtrate formed in all renal corpuscles of both kidneys per minute

Answer 15

125 mL/min

Question 16

what happens when GFR is too high

Answer 16

useful substances are lost due to the speed of fluid passage through nephron

Question 17

what happens when GFR is too low

Answer 17

sufficient waste products may not be removed from the body

Question 18

what is the formula for NFP

Answer 18

GBHP-CHP-BCOP

Question 19

what is required to maintain homeostasis

Answer 19

constant GFR

Question 20

what does NFP depend most heavily on

Answer 20

GBHP

Question 21

when does filtration stop

Answer 21

if GBHP drops from 55mmHg to 45 mmHg

Question 22

what is GBHP determined by

Answer 22

MAP

Question 23

what mean arterial pressure do kidneys normally function with

Answer 23

80mmHg and 180 mmHg

Question 24

what is auto regulation of GFR

Answer 24

mechanisms that maintain a constant GFR despite changes in arterial blood pressure

Question 25

what are the mechanisms in auto regulation of GFR

Answer 25

- myogenic mechanism | - tubuloglomerular feedback

Question 26

which mechanism of auto regulation is faster

Answer 26

myogenic

Question 27

what happens in myogenic mechanism

Answer 27

- systemic increases in blood pressure stretch the afferent arteriole - smooth muscle contraction reduced the diameter of the afferent arteriole returning the GFR to its previous level in seconds

Question 28

what happens in tubuloglomerular feedback

Answer 28

- elev Aten systemic blood pressure raises the GFR so that fluid flows too rapidly through the renal tubule, Na+ and Cl- are not reabsorbed - macula densa in ascending limb of loop of henle detects increased Na+ and Cl- which inhibits release of nitric oxide from juxtaglomerular apparatus - afferent arteriole constrict which reduces GFR

Question 29

what happens in neural regulation of GFR

Answer 29

- blood vessels of the kidney are supplied by sympathetic fibers that cause vasoconstriction of afferent arterioles - SNS will override renal autoregulation - SNS will also stimulate renin release from the juxtaglomerular cells

Question 30

in neural regulation what happens with no SNS activity

Answer 30

blood vessels are maximally dilated

Question 31

in neural regulation what happens with moderate SNS

Answer 31

bother afferent and efferent arterioles constrict equally

Question 32

in neural regulation what happens with extreme sympathetic stimujlation

Answer 32

vasoconstriction of afferent arteriole predominates

Question 33

what happens with extreme SNS

Answer 33

- GFR decreases substantially - lowers urine output to maintain blood volume - permits greater blood flow to other tissues

Question 34

what are the two hormones that contribute to regulation of GFR

Answer 34

atrial natriuretic peptide and angiotensin II

Question 35

what does ANP do

Answer 35

increases GFR

Question 36

how does ANP increase GFR

Answer 36

- stretching of the atria that occurs with an increase in blood volume causes hormonal release - relaxes glomerular mesangial cells increasing glomerular capillary surface area

Question 37

what does angiotensin II do

Answer 37

reduce GFR

Question 38

how does Angiotensin II reduce GFR

Answer 38

- activated by ACE in the lungs following the release of renin from juxtaglomerular cells - potent vasoconstrictor that narrow both afferent and efferent arterioles reducing GFR