Renal - Lecture 4

Question 1

What is osmolarity?

Answer 1

total solute concentration of a solution; measure of water concentration in that the higher the solution osmolarity, the lower the water concentration

Question 2

What is hypoosmotic?

Answer 2

having total solute concentration less than that of normal extracellular fluid (300 mOsm)

Question 3

What is isoosmotic?

Answer 3

having total solute concentration equal to that of normal extracellular fluid

Question 4

What is hyperosmotic?

Answer 4

having total solute concentration greater than that of normal extracellular fluid

Question 5

Water is ___ filtered.

Answer 5

freely

Question 6

How much of water is reabsorbed?

Answer 6

99%

Question 7

Where does the majority of water reabsorption occur?

Answer 7

in the proximal tubule

Question 8

Where does the major hormonal control of reabsorption of water occur?

Answer 8

CD

Question 9

What kind of process is water reabsorption?

Answer 9

passive

Question 10

What is the direction of movement of water in the proximal tubule?

Answer 10

tubular lumen -> interstitial fluid

Question 11

What happens to the osmolarity in the tubular lumen?

Answer 11

it decreases

Question 12

What happens to osmolarity in the interstitial fluid?

Answer 12

it increases

Question 13

Step 1 of water reabsorption:
Na is reabsorbed from the ___ ___ to the ___ ___ across the epithelial cells.

Answer 13

tubular lumen
interstitial fluid

Question 14

Step 2 of water reabsorption:
The local osmolarity in the lumen ___, while the local osmolarity in the interstitium ___.

Answer 14

decreases
increases

Question 15

Step 3 of water reabsorption:
This difference in osmolarity causes net diffusion of water from the ___ into the ___ ___.
via tubular cells’ plasma membranes via ___ ___.

Answer 15

lumen
interstitial fluid
tight junctions

Question 16

Step 4 of water reabsorption:
From the interstitium, water, sodium, and everything else dissolved in the interstitial fluid move together by ___ ___ into ___ ___.

Answer 16

bulk flow
peritubular capillaries

Question 17

When the water intake is small, the kidney reabsorbs ___ water.

Answer 17

more

Question 18

What is the urine output when the kidney reabsorbs more water?

Answer 18

0.4 L

Question 19

When water intake is large, the kidney reabsorbs ___ water.

Answer 19

less

Question 20

What is the urine output when the kidney reabsorbs less water?

Answer 20

25 L

Question 21

Where does the dynamic regulation of water reabsorption occur?

Answer 21

collecting duct

Question 22

What are the 2 critical components of the dynamic regulation of water reabsorption?

Answer 22

1. high osmolarity of the medullary interstitium
2. permeability of CD to water (regulated by vasopressin)

Question 23

The kidney has the ability to concentrate urine up to ___.

Answer 23

1400 mOsm/L

Question 24

Urinary concentration takes place as ___ ___ flows through the ___ collecting ducts.

Answer 24

tubular fluid
medullary

Question 25

What does urinary concentration depend on?

Answer 25

the hyperosmolarity of the interstitial fluid

Question 26

In the presence of ___, water diffuses out of the ducts into the interstitial fluid in the medulla to be carried away.

Answer 26

vasopressin

Question 27

The countercurrent multiplier system comes from the anatomical structure of the ___ ___ ___.

Answer 27

Loop of Henle

Question 28

The medullary interstitial fluid becomes hyperosmotic through the function of ___ ___.

Answer 28

Henle's loop

Question 29

Is the ascending limb thick or thin?

Answer 29

thick

Question 30

What kind of flow is found in the descending and ascending limb?

Answer 30

countercurrent

Question 31

The proximal tubule cells reabsorb Na and water cells ___.

Answer 31

proportionally

Question 32

What is the fluid that leaves the proximal tubule?

Answer 32

isoosmotic (300 mOsm)

Question 33

The thick ascending limb is very active in the reabsorption of ___.

Answer 33

NaCl

Question 34

The thick ascending limb is impermeable to ___.

Answer 34

water

Question 35

Near the ascending limb, the interstitial fluid becomes a bit ___.

Answer 35

hyperosmotic

Question 36

In the tubule of the ascending limb, it becomes ___.

Answer 36

hypoosmotic

Question 37

The descending limb does not reabsorb ___.

Answer 37

NaCl

Question 38

The descending limb is permeable to ___.

Answer 38

water

Question 39

In the descending limb, water gets pulled ___, into the ___.

Answer 39

away, interstitium

Question 40

The fluid in the descending limb becomes ___.

Answer 40

hyperosmotic

Question 41

After the movement of fluid, the osmolarity pattern is:

Answer 41

hyperosmotic -> hypoosmotic

Question 42

The interstitial osmolarity is identical to the ___ limb.

Answer 42

descending

Question 43

What are vasa recta?

Answer 43

blood vessels in the medulla

Question 44

What kind of structure are vasa recta?

Answer 44

hairpin-loop

Question 45

What is the function of the vasa recta?

Answer 45

it minimizes excessive loss of solute from the interstitium

Question 46

In addition to NaCl, ___ also contributes to medullary osmolarity.

Answer 46

urea

Question 47

Water reabsorption depends on the water permeability of the ___.

Answer 47

tubules

Question 48

What does the permeability of the epithelium depend on?

Answer 48

the tubular segment

Question 49

The proximal tubule has a ___ permeability to water.

Answer 49

high

Question 50

What does permeability largely depend on?

Answer 50

the presence of water channels in the plasma membrane (aquaporins)

Question 51

Water permeability in the ___ and ___ is subject to physiological control.

Answer 51

CCD and MCD

Question 52

What controls the water permeability in the CCD and MCD?

Answer 52

vasopressin

Question 53

What kind of hormone is vasopressin?

Answer 53

anti-diuretic hormone

Question 54

What is vasopressin produced by?

Answer 54

hypothalamic neurons

Question 55

Where is vasopressin released from?

Answer 55

posterior lobe of the pituitary gland

Question 56

What 2 receptors does vasopressin bind to?

Answer 56

GPCR V1 and V2

Question 57

Where is GPCR V1 found?

Answer 57

smooth muscle

Question 58

Where is GPCR V2 found?

Answer 58

kidney

Question 59

What does vasopressin stimulate the insertion of in the luminal membrane of the collecting duct cells?

Answer 59

aquaporins

Question 60

Where does vasopressin stimulate the insertion of aquaporins?

Answer 60

in the luminal membrane of the collecting duct

Question 61

What does vasopressin increase?

Answer 61

water permeability

Question 62

When vasopressin is present, collecting ducts become ___ to water ----> water ___

Answer 62

permeable reabsorption

Question 63

When vasopressin is not present, collecting ducts become ___ to water ----> water ___

Answer 63

impermeable diuresis

Question 64

What is diabetes insipidus caused by?

Answer 64

malfunction of the vasopressin system (vasopressin does NOT work)

Question 65

What regulates the rate of water reabsorption from the tubules?

Answer 65

vasopressin

Question 66

Vasopressin is a major regulator of water___.

Answer 66

excretion

Question 67

What are the two mechanisms to regulate vasopressin secretion?

Answer 67

1. Osmoreceptor control (most important) 2. Baroreceptor control (less sensitive)

Question 68

Excess H20 ingestion causes ___ in H20 excretion.

Answer 68

increase

Question 69

What happens to body fluid osmolarity and firing by hypothalamic osmoreceptors when excess H20 is ingested?

Answer 69

they decrease

Question 70

What happens to vasopressin secretion when excess H20 is ingested?

Answer 70

it decreases

Question 71

What happens to tubular permeability to H20 and H20 reabsorption when excess H20 is ingested?

Answer 71

it decreases

Question 72

What happens to venous, atrial and arterial pressures when plasma volume decreases?

Answer 72

it decreases

Question 73

What happens to vasopressin secretion when venous, atrial and arterial pressures decrease?

Answer 73

they increase

Question 74

What are the reflexes of the vasopressin secretion mediated by when venous, atrial and arterial pressures decrease?

Answer 74

cardiovascular baroreceptors

Question 75

What happens to tubular permeability to H20 and H20 reabsorption when plasma vasopressin increases?

Answer 75

they increase

Question 76

When plasma volume decreases, H20 excretion ___.

Answer 76

decreases

Question 77

What causes us to feel thirsty?

Answer 77

the increase in plasma osmolarity

Question 78

What senses an increase in plasma osmolarity and causes thirst?

Answer 78

osmoreceptors

Question 79

___ in plasma volume can be sensed by ___ to increase thirst.

Answer 79

decrease, baroreceptors

Question 80

What else can cause thirst?

Answer 80

dry mouth and throat

Question 81

What can decrease thirst?

Answer 81

metering of water intake by GI tract

Question 82

What does severe sweating cause a loss of?

Answer 82

hypoosmotic salt solution

Question 83

Loss of hypoosmotic salt solution causes an ___ in plasma volume and ___ in plasma osmolarity during severe sweating.

Answer 83

decrease increase

Question 84

When plasma volume decreases, the GFR ___ and plasma aldosterone ___ during severe sweating.

Answer 84

decreases increases

Question 85

The decrease of GFR and increase in plasma aldosterone cause ___ in sodium excretion during severe sweating.

Answer 85

decrease

Question 86

The increase in plasma osmolarity during severe sweating causes an ___ in plasma vasopressin.

Answer 86

increase

Question 87

The increase in plasma vasopressin during severe sweating causes a ___ in H20 excretion.

Answer 87

decrease