Glomerular Filtration and Renal Blood Flow

Question 1

how does the diameter of the afferent arteriole compare to that of the efferent arteriole

Answer 1

afferent arteriole has larger diameter

Question 2

what are the different barrier to glomerular filtration (3)

Answer 2

glomerular capillary endothelium(RBC barrier), basement membrane(plasma protein barrier) and the slit processes of podocytes(plasma protein barrier)

Question 3

what function does the -ve charge of the basement membrane of the glomerulus have

Answer 3

means that large plasma proteins can’t get through and so are retained

Question 4

what force works in favour of net filtration pressure at the glomerulus

Answer 4

the glomerular capillary blood pressure

55mm Hg

Question 5

what forces work against the net filtration pressure at the glomerulus

Answer 5

Bowman’s capsule hydrostatic pressure(15mm Hg) and capillary oncotic pressure(30mm Hg)

Question 6

what is glomerular filtration rate(GFR) defined as

Answer 6

Kf(filtration coefficient) x net filtration pressure

Question 7

describe the effect of vasoconstriction/dilatation on GFR

Answer 7

vasodilatation increases blood flow into glomerulus, increases glomerular capillary pressure and therefore increase GFR
(and vice versa)

Question 8

describe the negative feedback mechanism that effects GFR

Answer 8

increased GFR increases NaCl flow through tubule, this is sensed by macula densa and releases vasoconstrictors to reduce blood flow into glomerulus