lecture 33 - renal / urinary physiology

Question 1

what are the three places where water is reabsorbed in the nephron

Answer 1

• proximal convoluted tubule ( bulk reabsorption 67%)
• descending limb of nephron (25%)
• collecting duct (2-8%

Question 2

is bulk reabsorption of water para or transcellular

Answer 2

both

Question 3

is regulated reabsorption of water para or transcellular

Answer 3

only transcellular

Question 4

is bulk reabsorption of water regulated

Answer 4

no = automatic

Question 5

How is regulated reabsorption of water regulated

Answer 5

regulated by antidiuretic hormone, more ADH less urine

Question 6

what are the four important places where sodium is reabsorbed

Answer 6

• proximal convoluted tubule (67%)
• ascending limb of the nephron loop (25%)
• distal convoluted tubule (5%)
• collecting duct (2-3%)

Question 7

what is water reabsorption in the proximal tubule driven by

Answer 7

Na+ reabsorption

Question 8

what follows glucose and sodium being transported through the proximal tubule

Answer 8

• chloride follows via the paracellular pathway
• water follows by the paracellular and transcellular pathway

Question 9

what is the descending loop of the nephron permeable to

Answer 9

water (has aquaporins)

Question 10

what is the ascending loop of the nephron permeable to

Answer 10

ions (sodium)

Question 11

how is water reabsorbed from the nephron into the peritubular fluid

Answer 11

• via the transcellular pathway = aquaporins
• via the paracellular pathway = across junctions between cells

Question 12

how do the juxtamedullary nephrons generate of hyper-osmotic medullary gradient

Answer 12

the different permeabilities of the descending (water) and ascending (sodium) parts of the juxtamedullary nephron loop

Question 13

what regulated the absorption of sodium in the distal convoluted tubule and the collecting duct

Answer 13

aldosterone

Question 14

what detects change in body osmolarity

Answer 14

osmoreceptors in the hypothalamus

Question 15

how does ADH balance TBW

Answer 15

ADH alters the permeability of the collecting duct, so water is retained/excreted to balance the initial change in TBW

Question 16

what will the hypothalamus do in the posterior pituitary if there is a decrease in TBW

Answer 16

increase in ECF osmolarity so posterior pituitary will increase release of ADH

Question 17

what will increase in ADH secretion do

Answer 17

insertion of aquaporins in apical membrane of CD cells : increase in water permeability

so therefore increase in water reabsorption, decrease in urine

Question 18

what does an increase in ECF volume mean in terms of released hormone

Answer 18

release of ANP into the kidney

Question 19

what does the release of ANP cause

Answer 19

increase of Na+ loss in urine
increased water loss in urine

Question 20

what happens when there is decreased ECF volume (receptors in the kidneys)

Answer 20

baroreceptors in the kidneys will activate release of aldosterone (RAAS)

Question 21

what does increased release of aldosterone to

Answer 21

increased sodium channels in apical membrane of DCT and CD

• so decreased Na+ in urine
• decreased water loss in urine

Question 22

how does aldosterone increase sodium and water reabsorption

Answer 22

increase sodium channels in apical membrane of DCT or CD

Question 23

what is pH of someones normal urine following an average diet

Answer 23

6-7.5

Question 24

what are things that are found in pathological urine

Answer 24

• glucose
• protein
• blood
• bacteria
• white blood cells
• haemolgobin