3/4: Renal Physiology - DiSole

Question 1

cortical v. juxtamedullary nephrons

Answer 1

cortical- nephrons that have glomeruli located in the outer cortex and short loop of henle
- uses peritubular capillaries

juxtamedullary - nephrons that have glomeruli located deep in cortex an d long loop of henle (20-30%)

• uses the vasa recta
• assoc with concentrated urine

Question 2

GFR is determined by…

Answer 2

net filtration pressure

glomerular capillary filtration fraction coefficient

Question 3

net filtration pressure is determined by sum of …

Answer 3

hydrostatic forces
colloid osmotic forces

across the glomerular membrane

Question 4

forces favoring filtration =

forces opposing filtration =

Answer 4

favor: glomerular hydrostatic pressure
opposing: glomerular colloid osmotic pressure and bowman’s capsule pressure

Question 5

vasoconstriction of AA leads to _______ GFR

vasoconstriction of EA leads to ___ GFR

vasodilation of EA leads to _______ GFR

vasodilation of AA leads to _______ GFR

Answer 5

decreased

increased

decreased

increased

Question 6

where are glucose and aa reabsorbed?

Answer 6

proximal tubule

Question 7

substances where amount secreted is greater than filtered?

Answer 7

potassium
proton organic acids
urea, urate

Question 8

best parts of nephron for reabsorption

Answer 8

proximal tubule (isosmotic) and thick ascending loop of henle (hyposmotic)

thick cells with microvili and mitochondria

compare to thin descending loop of henle which has thin cells and is only permeable to water

Question 9

distal tubule and collecting has two types of cells

Answer 9

prinicipal

intercalated – important for potassium

Question 10

net re-absorptive forces in peritubular capillary/interstitial fluid

Answer 10

favor: capillary colloid osmotic pressure and interstitial fluid hydrostatic pressure
opposing: peritubular capillary hydrostatic pressure and interstitial fluid collloid osmotic pressure

Question 11

basic requirements for forming a concentrated urine are…

Answer 11

• high osmolarity of renal medullary interstitial fluid

- high level of ADH/vasopressin

Question 12

function of vasa recta

Answer 12

counter current exchangers minimizing washout of solutes from the interstitium

Question 13

an increase in fluid osmolaltiy, plasma sodium concentartion causes osmoreceptor cells to …

Answer 13

shrink –> signals the suproptic nuclei that release ADH

ADH will increase concentration of urine (retain water)

Question 14

how do we know that renal auto-regulation exists?

Answer 14

range of changing renal perfusion pressure over which the GFR and renal blood flow do not change

Question 15

tubules respond to glomeruli with the…

Answer 15

glomerulotubular balance (achieved by tubules via changes in hydrostatic and colloid osmotic forces and luminal factors)

the glomeruli respond to tubules through the tubuloglomerular feedback

GTB and TGF feedback systems stabilize single nephron GFR and distal fluid and electrolyte delivery

Question 16

describe tubuloglomerular feedback

Answer 16

• fluctuation in NaCL delivery to distal tubule sensed by juxtaglomerular apparatus which then changes afferent or efferent arteriolar resistance

Question 17

3 stimuli for release of renin from juxtaglomerular cells

Answer 17

• macula densa mechanism (tubuloglomerular feedback)
• sympathetic n. mechanism (stimulates release)
• baroreceptor mechanism (increased affarent arteriole pressure inhibits renin release, reverse also)

Question 18

3 main effects of angiotensin II

Answer 18

• constrict efferent arterioles
• stimulate aldosterone secretion
• directly stimulate sodium tubular re-absorption

Question 19

effects on aldosterone secretion

high Na intake –
high K intake –

Answer 19

decreases

increases

Question 20

secreted by cardiac atria cells in volume expansion conditions

Answer 20

ANP – inhibits reabsorption of sodium and water by renal tubules especially the collecting ducts

Question 21

an increase in activity of renal sympathetic n. results in an increase of sodium and wataer re-asbsorption due to …

Answer 21

reduction in GFR by constriction of arterioles

increase in tubular sodium re-absorption

increase in renin release and angiotensin II formation more more tubular re-absorption