Tubular Transport II

Question 1

Water loss from body

Answer 1

sweat, respiration, feces, urine, vomit

Question 2

Water gain to body

Answer 2

oral

Question 3

The amount of water that leaves the body affects the

Answer 3

plasma osmolality

Question 4

ECF Volume is a reflection of the

Answer 4

Body Na content

Question 5

ECF volume is sensed by

Answer 5

arterial and cardiac baroreceptors

Question 6

Low/High ECF volume triggers

Answer 6

Ang II, aldosterone, SNS/ANP

Question 7

Low/High ECF volume leads to the

Answer 7

excretion or retention of Na

Question 8

Plasma osmolality is a reflection of the

Answer 8

body water content of body fluid

Question 9

HIgh/Low Plasma osmolality is sensed by

Answer 9

hypothalamic osmoreceptors

Question 10

High/Low Plasma osmolality leads to the

Answer 10

excretion of H2O or intake of H2O (thirst)

Question 11

A problem with total body water manifests as

Answer 11

plasma osmolality alteration [Na]

Question 12

problems with total body Na content manifest as

Answer 12

ECF volume alteration

Question 13

Diuresis

Answer 13

excretion of large amounts of urine (hypoosmolar)

Question 14

Antidiuresis

Answer 14

excretion of small amount of urine (hyperosmolar)

Question 15

Normal plasma osmolality is

Answer 15

275-295

Question 16

ADH release is triggered by

Answer 16

atrial or arterial baroreceptors

Question 17

ADH is released from the __________ due to signals from __________

Answer 17

posterior pituitary; hypothalamic osmoreceptors

Question 18

Osmoreceptors in the hypothalamus sense change sin

Answer 18

plasma osmolality

Question 19

Low plasma osmolality –>

Answer 19

reduced ADH –> decreased reabsorption of H2O in the collecting duct

Question 20

When plasma osmolality is <280 , ADH is

Answer 20

almost 0!

Question 21

High plasma osmolality –>

Answer 21

increased ADH –> increased reabsorption of water (AQP-2)

Question 22

ADH mechanism

Answer 22

binds to vasopressin-2 (V2) receptor on principal cells –> increased cAMP –> increased AQP-2 –> H2O reabsorption

Question 23

What 2 things are necessary to concentrate urine?

Answer 23

ADH and permeable distal tubule and collecting duct AND hypertonic medullary gradient

Question 24

What establishes the hypertonic medullary gradient?

Answer 24

thick ascending limb reabsorption of solutes (NaCl and urea)

Question 25

Countercurrent multiplication

Answer 25

arrangement of loop of Henle and the collecting duct, creates a gradient as the loop dips deeper into the medulla

Question 26

Dilution of urine requires 2 things

Answer 26

reabsorption of solutes (W/O H2O) in the thick ascending limb AND low levels of ADH

Question 27

Concentration of urine step-wise

Answer 27

isoosmolar (300) filtrate in descending limb loses H2O to become hyperosmolar (600), NaCl is lost in the thin ascending limb and Na-K-Cl reabsorbs solute in the thick ascending limb to create a hypoosmolar filtrate (150), NaCl is reabsorbed in the distal tubule and collecting duct (W/O H2O loss) concentrating the urine to 50mOsm

Question 28

Concentrating the urine step-wise

Answer 28

isoosmolar (300) filtrate in descending limb loses H2O to become hyperosmolar (600), NaCl is lost in the thin ascending limb and Na-K-Cl reabsorbs solute in the thick ascending limb to create a hypoosmolar filtrate (150), in the presence of ADH H2O can rapidly move down it's concentration gradient in the distal tubule and collecting duct until it equilibrates with its surrounding (1200mOsm)

Question 29

What happens if the NaCl reabsorption out of the thick limb is impaired?

Answer 29

hypertonic gradient cannot be established and concentrating the urine cannot take place

Question 30

Role of Urea in medulla osmolality

Answer 30

In conditions of severe dehydration, ADH phosphorylates urea transporters (UT-A1) in the thick ascending limb and allows for the resorption of Urea. Contributing to the maximal ability to concentrate the urine.

Question 31

How would a high protein diet effect the ability to concentrate urine?

Answer 31

High protein, high urea in filtrate, higher medullary interstitial, greater ability to concentrate urine.

Question 32

How would consuming large amounts of water contribute to the ability to concentrate urine?

Answer 32

Large amounts of water, large amounts of flow in vase recta, "washing-out" of solutes in hypertonic medulla --> decreased ability to concentrate urine

Question 33

Why isn't the maximum medullary osmolarity 1200 during diuresis?

Answer 33

Low ADH --> less urea in interstitial, and large volume flow through the vasa recta "washes-out" hypertonic medulla

Question 34

If vasa recta blood flow is decreased, what will happen to the concentrating ability of the kidney?

Answer 34

decreased blood flow, decreased ATP and O2 for Na reabsorption, decreased osmolality of interstium, DECREASED ability to concentrate urine

Question 35

Comparison of urine osmolality to plasma osmolality tells you if you are concentrating or diluting the urine

Answer 35

hypoosmolar: Uosm < Posm (dilute urine) isoosmolar: Uosm = Posm Hyperosmolar: Uosm > Posm (concentrating urine)

Question 36

Free water clearance

Answer 36

(+) Ch2o added to urine to make it dilute | (-) Ch2o retained to make urine concentrated

Question 37

Negative water clearance is called

Answer 37

TcH2O (tubular conservation of H2O)

Question 38

Positive water clearance is called

Answer 38

CH2O