! physiology

Question 1

part of the kidney thats esp important in kidneys ability to produce urine of varying concentration

Answer 1

loop of henle

Question 2

which factor would reduce the net filtration pressure the most?

Answer 2

a large increase in blood colloid osmotic pressure

Question 3

which forces oppose netfiltration?

Answer 3

• Bowmans capsule hydrostatic – opposes filtration

- Capillary oncotic – plasma proteins trapped in lumen tries to attract fluid from bowmans capsule

Question 4

osmotic vs oncotic

Answer 4

osmotic pressure = the pressure needed to stop the net movement of water across a permeable membrane which separates the solvent and solution

oncotic pressure = the contribution made to total osmolality by colloids.

Question 5

affect of afferent arteriolar vasoconstriction on blood flow, netfiltration + GFR

Answer 5

Afferent arteriolar vasoconstriction decreases blood flow into the glomerulus
which causes the glomerular-capillary blood pressure to decrease
leading to a decrease in the net filtration pressure
and a resultant decrease in the GFR

Question 6

When arterial blood pressure is elevated above normal, which of the following compensatory changes in renal function occur as a result of the baroreceptor reflex?

Answer 6

afferent arteriolar vasodilation

Question 7

why cant serum albumin be filtered at glomerulus?

Answer 7

its negative + basement membrane also neg

Question 8

hydrostatic vs oncotic

Answer 8

hydrostatic = balloon = pushes fluid out

oncotic = sponge = draws fluid in

Question 9

what is the renal threshold?

Answer 9

= plasma concentration of a particular substance at which its Tm is reached and the substance first appears in the urine

(Renal threshold = the concentration of a substance dissolved in the blood above which the kidneys begin to secreted into urine)

RT of gluc = 10-12 mmol/l

Question 10

aldosterone

Answer 10

stimulates Na reabsorption in distal + collecting tubules

+ stimulates K secretion in distal tubule

Question 11

potassium (throughout the nephron)

Answer 11

• is filtered, reabsorbed + secreted
• is actively reabsorbed in proximal tubule (NaKATPase)
• is actively secreted in distal + collecting tubules (Na-K-2Cl)
• secretion is controlled by aldosterone

Question 12

what establishes the medullary vertical osmotic gradient by means of countercurrent multiplication?

Answer 12

loops of Henle of juxtamedullary nephrons

Question 13

tonicity of tubular fluid from Bowmans capsule to end of loop of Henle

Answer 13

bowmans capsule = isotonic
proximal tubule = isotonic

tip of loop = hypertonic
leaving loop = hypOtonic

Question 14

which segment of the nephron is not permeable to H2O even in the presence of vasopressin?

Answer 14

ascending limb of loop

Question 15

how does urine move from the kidneys to the urinary bladder through the ureters?

Answer 15

by peristaltic contraction of the smooth muscle of the ureters

Question 16

filtration fractions

Answer 16

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

= GFR/renal plasma flow = 125/650 = 20% normally

(remaining 80% moves onto peritubular capillaries)

Question 17

capillaries in cortical vs juxtamedullary nephrons

Answer 17

cortical = peritubular capillaries

juxtamedullary nephron = vasa recta

Question 18

where is sodium reabsorbed from in nephron?

Answer 18

everywhere except descending part o loop of henle

Question 19

what drives resoption of Na?

Answer 19

Na-K ATPase

Question 20

methods of sodium reabsorption in proximal tubule

Answer 20

1. Na dependent glucose transporter - both Na + gluc in
2. Na dependent amino acid transports - both in
3. Na + H(countertransporter) - Na in, H out

Question 21

effect of Na reabsorption on Cl- ions

Answer 21

Reabsorption of Na ions via the transcellular route sets up an electrochemical gradient that allows passive paracellular reabsorption of negatively charged chloride ions(Cl-)

• Meaning NaCl reabsorbed to blood which sets up
  osmotic gradient
• Water follows NaCl passively + via paracellular

Question 22

transport maximum

Answer 22

max rate at which substance can be reabsorbed

Question 23

water permability in descending vs ascending loop

Answer 23

descending = permeable, no salt reabsorption

ascending = impermeable, salt resorption

• -> passive in thin, active in thick
• -> no water follows due to tight tight junctions

Question 24

recycling of K after transport by Na-K-2Cl allows for what

Answer 24

NaCl is absorbed into interstital fluid

Question 25

what sets up and maintains the cortico-medullary osmotic gradient respectively?

Answer 25

sets up = loop of henle

maintains it = vasa recta

Question 26

What is the purposed of the countercurrent multiplication?

Answer 26

concentrate medullary interstitial fluid

Question 27

why does the medullary interstitial fluid need concentrating?

Answer 27

to enable kidneys to produce urine of different volume + conc according to amounts of ADH

(dependent on bodys hydration status)

Question 28

components of countercurrent system

Answer 28

countercurrent multiplier = loop of henle

countercurrent exchanger = vasa recta

Question 29

does ADH increase or decrease urine production?

Answer 29

decreases -> ANTIdiuretic

conserves water

Question 30

aldosterone increases the absorption + secretion of what respectively?

Answer 30

increases Na reabsorption

increases K/H secretion
–> (spironolactone can cause hyperkalaemia)

Question 31

affect of atrial netriuretic hormone

Answer 31

decrease Na reabsorption

opposite to aldosterone

Question 32

effect of PTH on Ca + phosphate

Answer 32

increases Ca reabsorption

decreases phosphate reabsorption

Question 33

where is the Na-K-2Cl triple cotransporter present?

Answer 33

thick ascending loop

–> blocked by loop diuretics

Question 34

the inhibitory effect of parathyroid hormone on renal phosphate reabsorption.
At what site in the kidney is parathyroid hormone likely to be having the greatest effect to cause these blood results?

Answer 34

Proximal convoluted tubule
-> Majority of renal phosphate reabsorption occurs in the proximal convoluted tubule
(why parathyroid hormone is having greatest effect here)