renal 5

Question 1

why does a high protein diet enable people to concentrate their urine better than people with low protein intake

Answer 1

• high protein = more urea and better able to concentrate urine

Question 2

where is urea reabsorbed in the kidney

Answer 2

• 50% absorbed in the proximal tubule
• 60% more reabsorbed in the medullary collecting ducts (depends on amount of ADH which activates urea transporters)
• the remaining 40% gets excreted

Question 3

which part of the loop of henle reabsorb sodium and chloride

Answer 3

• thick ascending LOH

Question 4

when part of loop of henle is permeable to water

Answer 4

• thin descending limb of LOH

Question 5

which part of loop of henle is impermeable to water

Answer 5

• thick and thin ascending LOH

Question 6

which part of nephron is responsible for a counter current

Answer 6

• loop of henle

- creates a contercurrent gradient

Question 7

which portion of the kidney structure performs the countercurrent exchange

Answer 7

• Vasa recta

Question 8

describe the countercurrent exchange

Answer 8

• passive transport allows NaCl and Urea into the vasa recta near the tip (bottom) of the loop
• water is forced out into the interstitium
• as the tube comes back up, interstitial osmolality decreases and NaCl and urea passively move out and water passively moves in
• the blood entering venous circ. has a higher (slightly) osmolarity than the blood entering the vasa recta

Question 9

what is the effect of ADH concentration on the cortical collecting ducts and meduallary collecting ducts

Answer 9

• cortical collecting ducts = responsive to ADH and allows the development of highest osmolarity possible
• Medullary colleting ducts = responsive to ADH and allows the urine to be concentrated when ADH is present

Question 10

What are the compensatory responses to dehydration?

Answer 10

• Dehydration = decreased blood volume (BP) but increased osmolarity
• -> causes increase in ADH release (changes in osmolarity more so than blood vol.)
• -> also means less atrial stretch stim causing release of ADH to increase BP

Question 11

define central diabetes insipidus

Answer 11

• hypothalamus does not create ADH

Question 12

define nephrogenic diaetes insipidus

Answer 12

• lack ADH receptors/aquaporins etc

Question 13

why does diabetes insipidus can cause excretion of large amounts of dilute urine

Answer 13

lots of dilute urine excreted since they can’t take advantage of medullary gradient to reabsorb water from collecting ducts

Question 14

describe SIADH

Answer 14

• SIADH = syndrome of inappropriate antidiuretic hormone secretion
• excessive release of ADH, results in hyponatremia (plasma Na lowered)
• assocaited with small cell carcinoma of lung (tumor secretes ADH)

Question 15

how does ethanol and morphine effect the release of ADH

Answer 15

• ethanol DECREASES ADH secreation

- morphine INCREASES ADH secretion