Concentration and dilution of urine Lecture 48

Question 1

What are parameters for hyperosmotic urine?

Answer 1

> 300mOsm/L

Question 2

What are parameters for hypoosmotic urine?

Answer 2

<300 mOSm/L

Question 3

what are parameters for isosmotic urine?

Answer 3

=300 mOsm/L

Question 4

What does osmoregulation or the amount of water retained excreted depend on?

Answer 4

ADH

Question 5

ADH is synthesized in the_______ and stored in the ________ and released if plasma osmolarity is high or fluid loss >10%.
the V1 receptor is for _________.
the V2 receptor is for ___________.

Answer 5

hypothalamus

posterior pituitary

vasoconstriction

water retention

Question 6

How much solute waste must be excreted in the urine per day?

Answer 6

600 mOsm/ day

minumum urine volume is 0.5 L per day

= obligatory volume

Question 7

How much is normal urine volume ?

Answer 7

1.5-2.5 L per day

Question 8

What are the three processes that contribute to corticopapillary osmotic gradient?

Answer 8

1. countercurrent multiplication
2. urea recycling
3. slow rates flow

Question 9

Generation and maintenance of osmotic gradient is due to?

Answer 9

-ATP dependent solute transport
-increase in medullary osmolarity
-Slow tubular fluid flow
this occurs throughout the length of the loop

+++ theres a 200mOsm gradient difference between the tubule and the interstitium

Question 10

In the presence of ADH what occurs to Urea? explain what urea cycling is?

Answer 10

as H2O is reabsorbed from the Collecting duct, urea concentration rises.
ADH unregulates UTA1 and UTA3 transporters.
Urea diffuses passively via transporters into the interstitium.
- some of it is secreted into both thin loops of Henle
This is called urea recycling
50% absorbed in the proximal tubule
then of the 50% of the one left in the lumen after recycling 20 % is excreted

Question 11

______ is necessaire for increasing osmolarity of the inner medullar. it contributes half of the hyperosmotic gradient used in the counter current multiplier/

Answer 11

Urea

Question 12

Urea is ______reabsorbed from the tubule and requires _____.

Answer 12

passively, ADH

Question 13

what are the counter current excHANGERS?
what occurs down stream?
what occurs up stream?

Answer 13

VASA RECTA, no energy is required to do the counter current exchange here.

down stream gains NaCl and losses water so plasma osmolarity increases to 1200 most at the tip of the medulla.

Upstream it Gains water and loses salt so plasma restores 300mOsm it drains into systemic circulation

Question 14

What occurs to collecting duct with low ADH?

Answer 14

• the collecting duct is impermeable to water
• No Urea reabsorption
• Medulla slightly hyperosmotic

Question 15

What occurs to collecting duct with high ADH?

Answer 15

• Collecting duct permeable to water (AQP2)
• Urea reabsorption
• Medulla highly hyperosmotic

Question 16

What occurs when water conservation fails in Diabetes insidious?
what is the difference between nephrogenic and central DI?

Answer 16

ADH deficiency

Nephrogenic DI:

• V2 receptor mutations; AQP2 mutations
• acquired ex; lithium therapy

Central DI:

• congenital lack of ADH production
• acquired; head trauma

Question 17

Rate if excretion equation

Answer 17

Ux*V

urine concentration of substance X * flow rate of urine

Question 18

Clearance equation

Answer 18

Cx=Ux*V/ Px

Ux= urine concentration of substance X
V= urine flow rate 
Px= plasma concentration of substance X

Question 19

Volume of plasma cleared of solutes equation

Answer 19

check card

Question 20

Volume of plasma cleared of solutes equation

Answer 20

check card

Question 21

Free water clearance

Answer 21

indicates the kidneys ability to concentrate or dilute urine
look at card for equation/ use slides to practice

if the answer=0 isoosmotic
+= hypoosmotic
-= hyperosmotic