4.4_2 Renal II

Question 1

Does the medulla have high or low osmolarity?

Answer 1

HIGH

Question 2

Osmolarity =

Answer 2

Osmoles / liter

Question 3

What is the osmolarity of 150 nM NaCl? (in most / L)

Answer 3

300

Question 4

What is the medulla’s saltiness due to?

Answer 4

The countercurrent multiplier system in the Loop of Henle

Question 5

Three essential features of the countercurrent multiplier system in the Loop of Henle

Answer 5

1. Filtrate countercurrent
2. Differential water permeability
3. Countercurrent blood flow

Question 6

Filtrate countercurrent

Answer 6

Tubular fluid flows in the opposite direction in descending and ascending limbs

Question 7

Differential water permeability

Answer 7

Ascending and descending limb have different permeabilities to water

Question 8

Is the ascending limb permeable to water?

Answer 8

No, it is thick and impermeable to water

Question 9

What does the ascending limb do?

Answer 9

Actively transports ions out of the tubular fluid into the interstitial space

Question 10

Is the descending limb permeable to water?

Answer 10

Yes, the entire limb is permeable to water

Question 11

Countercurrent blood flow

Answer 11

Blood in vasa recta also flows in opposite direction to the tubular fluid

Question 12

In the ascending limb, __________ transport NaCl at ________ membrane… drags NaCl out of filtrate across _______ into ________

Answer 12

ATP driven pumps
Basolateral
Tubule epithelial cells
Interstitial space

Question 13

First step of counter current multiplier

Answer 13

Pumps Na+ from filtrate into surrounding interstitial space

Water can’t follow

Question 14

Is filtrate entering the DCT dilute or salty?

Answer 14

Dilute

Question 15

What happens with the vasa recite near the ascending limb?

Answer 15

Water from plasma chases salt into interstitial space, vasa recta plasma becomes saltier as it heads towards descending limb

Question 16

Why does the water in filtrate move out in the descending limb?

Answer 16

Because it is
Chasing salt pumped out by ascending limb in interstitial space
Chasing salty blood in vasa recta

Question 17

Vasa recta by the descending limb

Answer 17

Some salts leave chasing water from filtrate (adds salt to interstitial space)

Question 18

What happens to the water left in the vasa recta

Answer 18

Re-enters blood, gets whisked aways to the heart

Question 19

The combination of the Loop of Henle and vasa recta capillaries establish…

Answer 19

An osmotic gradient

Question 20

What is the osmolarity of the interstitial fluid at the base of the Loop of Henle?

Answer 20

~1200 mOsmoles

-Super salty!

Question 21

Is the filtrate salty or dilute at the base of the loop of Henle?

Answer 21

Very salty, but it does not matter because the salt will be extracted as it rises up the ascending limb

Question 22

The filtrate is ~___mOsmoles ay the end of the Loop

Answer 22

100

Question 23

Blood Osmolarity is regulated by…

Answer 23

Water retention (ADH)

Question 24

Blood volume is regulated by

Answer 24

Retention of salts

Na, K (Aldosterone and Atrial Natriuretic Petide))

Question 25

Sensor cells for osmolarity are in the...

Answer 25

Hypothalamus.. ADH neurons

Question 26

Effectors for osmolarity regulation

Answer 26

The epithelial cells lining the collecting duct express ADH receptor

Question 27

The hypothalamic cells release _____ which controls how _______ the ______ is to water

Answer 27

ADH Permeable Collecting duct

Question 28

Hypothalamic _______ integrate signals for osmolarity

Answer 28

Osmoreceptors

Question 29

ADH is produced in ________ cells in hypothalamus and released in _________

Answer 29

Neurosecretory | Posterior pituitary

Question 30

_______ cells in collecting duct respond to ADH by increasing expression of _______

Answer 30

``` Principal Water channels (aquaporins) ```

Question 31

Water deficit = _______ --> Stimulates high plasma _____ --> Promotes water reabsorption in ________

Answer 31

High osmolarity ADH Collecting duct

Question 32

Do collecting ducts have more or less aquaporins open when ADH is expressed?

Answer 32

More, this makes it more permeable to water

Question 33

Why does water leave the collecting duct and enter the interstitial fluid?

Answer 33

Because of the saltiness that the Loop of Henle creates

Question 34

Water excess = ______, low plasma _____ --> Water lost to the urine

Answer 34

Low osmolarity | ADH

Question 35

When ADH is not expressed, collecting ducts are _____ to water, causing..

Answer 35

Impermeable | Water to pass by the salty medulla