74: Conc. & Dilution of Urine

Question 1

What happens during dehydration?

Answer 1

Increase in plasma osmolarity (concentrated)

Question 2

What happens during over hydration?

Answer 2

Decrease in plasma osmolarity (diluted)

Question 3

What receptors in the anterior hypothalamus are stimulated or inhibited to normalize plasma osmolarity?

Answer 3

Osmoreceptors

Question 4

Hyperosmotic urine

Answer 4

Osmolarity higher than plasma osmolarity (300 mOsm/L)

Question 5

Hypoosmotic urine

Answer 5

Osmolarity lower than plasma osmolarity (300 mOsm/L)

Question 6

Which components of nephron control dilution/concentration of urine?

Answer 6

Ascending loops
Late distal tubule
Collecting duct

Question 7

What is the osmotic gradient of urine?

Answer 7

300 – 1200 mOsm/L

Question 8

What is the interstitial osmolarity of the cortex?

Answer 8

Isosmotic

300 mOsm/L

Question 9

What is the interstitial osmolarity of the medulla?

Answer 9

Hyperosmotic

600 or 1200 mOsm/L

Question 10

What two processes that contribute to corticopapillary osmotic gradient?

Answer 10

Countercurrent multiplication

Urea recycling

Question 11

What factors generate and maintain the Osmotic Gradient?

Answer 11

ATP-dependent solute transport

Increase in osmolarity in medullary interstitium

Slow tubular fluid flow

Question 12

Which ions are actively removed in the thick portion of the ascending limb?

Answer 12

Na+ & Cl-

Question 13

How do Na+ & Cl- leave in the think ascending limb?

Answer 13

Diffusion

Question 14

____ moves from
descending limb to
equilibrate increasing
interstitial concentrations

Answer 14

H2O

Question 15

What part of the nephron concentrates the filtrate?

Answer 15

Loop of Henle

Question 16

Countercurrent Exchanger in Vasa Recta

Answer 16

Passive - no energy

Return solute and H2O back to circulation

Question 17

Which hormone is released during dehydration?

Answer 17

ADH

Question 18

Where is ADH released from?

Answer 18

Posterior pituitary

Question 19

What does ADH do in the nephron?

Answer 19

Increases H2O permeability in the distal tubules and collecting ducts

Increases H2O reabsorption into blood

Decreases urination frequency

Urine more concentrated

Question 20

What is another name for ADH

Answer 20

Vasopressin

Question 21

Which parts of the nephron are ADH dependent?

Answer 21

Late distal tubule

Cortical collecting duct

Outer medullar collecting duct

Inner medullary collecting duct

Question 22

Low ADH does what to urine flow rate?

Answer 22

Increases (High flow rate)

Question 23

High ADH does what to urine flow rate?

Answer 23

Decreases (Low flow rate)

Question 24

Syndrome of inappropriate antidiuretic hormone

Answer 24

SIADH

Question 25

Defect or damage to the thirst mechanism in the hypothalamus resulting in abnormal increase in thirst and fluid intake that suppresses
ADH secretion and increases urine output

Answer 25

Dipsogenic diabetes insipidus

Question 26

only occurs during pregnancy where mothers produce vasopressinase in the placenta, which breaks down ADH

Answer 26

Gestational diabetes insipidus

Question 27

Recirculation of Urea

Answer 27

ADH dependent

Urea reabsorbed into interstitial then secreted back into ascending limb

Question 28

What are the urea transporters on the collecting duct?

Answer 28

UT-A1 & UT-A3

Question 29

What contributes to half of the interstitial gradient at the base of Loop of Henle?

Answer 29

Urea (600 mOsm)

Question 30

If no ADH is present then what is the interstitial gradient at the Loop of Henle?

Answer 30

600 mOsm because urea is not contributing

Question 31

Clearance of Urea when ADH present

Answer 31

low urea excretion & low urine flow rate

Question 32

Clearance of Urea when NO ADH present

Answer 32

high urea excretion & high urine flow rate

Question 33

How does urea move?

Answer 33

Passive transport

Question 34

What increases Na+/K+/Cl transporter effectiveness?

Answer 34

ADH