Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PHGY 210 > Renal IV > Flashcards

Renal IV Flashcards

1
Q

How much water is filtered and reabsorbed?

A

It is freely filtered but 99% is reabsorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where does the majority of water reabsorption occur?

A

The proximal tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does hormonal control of reabsorption of water occur?

A

In the collecting duct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain how water reabsorption works in the proximal tubule.

A

It depends on Na+ reabsorption. Since Na+ has been moved from the tubule to the interstitial fluid, the osmolarity of the tubule has INCREASED and the osmolarity of the interstitial fluid has DECREASED.

This osmolarity gradient drives water from the tubular lumen to the interstitial fluid. This can occur paracellularly and transcellularly

The water along with sodium and other things dissolved in it will then enter the peritubular capillaries via bulk flow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Does water reabsorption happen transcellularly or paracellularly?

A

Both.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When water intake is small, the kidney will reabsorb [more/less] water. When water intake is large, the kidney will reabsorb [more/less] water.

A

More, less

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where does dynamic regulation of water reabsorption in response to intake occur in the tubule?

A

This takes place in the collecting duct.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the 2 components of the dynamic regulation of water reabsorption in the CD?

A
  1. High osmolarity of the medullary interstitium
  2. Permeability of CD to water (regulated by vasopressin)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the maximum concentration of the urine in the kidney?

A

1400 mOsm/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where does urinary concentration take place?

A

It takes place as tubular fluid flows through the medullary collecting ducts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Urinary concentration depends on […]

A

The hyperosmolarity of the medullary collecting duct interstitial fluid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Medullary interstitial fluid becomes hyperosmotic through the […], which occurs in […]

A

Countercurrent multiplier system, Henle’s loop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is countercurrent flow?

A

It is the flow of fluid down and then top the descending and ascending limbs respectively of Henle’s loop.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the ascending and descending limbs of Henle’s loop:
a) Reabsorption of NaCl
b) Permeability to water

A

Descending loop:
a) Does not reabsorb NaCl
b) Permeable to water

Ascending loop:
a) Actively reabsorbs NaCl
b) Impermeable to water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe how the countercurrent multiplier system works prior to a move.

A
  1. Isotonic water (300 mOsm) flows into the descending limb
  2. Once it reaches the ascending limb, NaCl gets reabsorbed. This leaves the water hypotonic and the interstitial fluid hypertonic.
  3. Since the descending limb is permeable to water, water will flow out and into the interstitial fluid to balance the osmolarity gradient.
    Result: descending limb - 400 mOsm, ascending limb 200 mOsm, interstitial fluid - 400 mOsm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe how the countercurrent multiplier system works after a move (assume hypertonic descending limb = 400 mOsmand hypotonic ascending limb = 200 mOsm)

A
  1. New isotonic water (300 mOsm) flows into the descending limb. The hypertonic water (400 mOsm) has been partially shifted into the ascending limb. The interstitial fluid is still hypertonic (400 mOsm).
  2. There is now an osmolarity gradient in the descending limb (300 -> 400) and in the ascending limb (400 -> 200)
  3. Na+ will move out of the ascending limb into the interstitium at the bottom, causing it to become more hypertonic.
  4. Water will then move out of the descending limb, increasing its osmolarity to match the interstitium.
17
Q

Describe the steady state of the countercurrent multiplier system.

A

The top of the loop is isoosmotic and it gets more hyperosmotic as you go down, eventually reaching 1200 mOsm. The ascending limb is more hypoosmotic than the interstitum and descending limb, which are equal.

18
Q

In the countercurrent multiplier system, where do active transport and diffusion occur?

A

Diffusion occurs on the descending limb, while active transport occurs on the ascending limb.

19
Q

What is the vasa recta? Describe its appearance and location.

A

The vasa recta is the blood vessels in the medulla. It has a hairpin-like structure that is very similar to that of the loop of Henle.

20
Q

What is the function of the vasa recta?

A

it minimizes excessive loss of solute from the interstitium in the countercurrent multiplier system.

21
Q

What is the function of urea in water balance in the urine?

A

Similar to NaCl, it also contributes to medullary hyperosmolarity.

22
Q

What is the consequence of the hyperosmolarity of the interstitial fluid in the medulla?

A

Water wants to flow out of the tubule. However, they can only happen if the tubule is permeable to water.

23
Q

Water permeability in the tubule is regulated by […]

A

The amount of aquaporins in the plasma membrane

24
Q

Describe the permeability of different parts of the tubule to water reabsorption. Include whether this state is permanent or not.

A

Proximal tubule: 67% (always permeable)
Descending limb: 15% (always permeable)
Ascending limb: never permeable
Distal tubule: never permeable
CCD and MCD: depends - permeability is subject to hormonal control via vasopressin.

25
Q

Where is water reabsorption regulated? By what?

A

The CCD and MCD. The regulation is hormonal, mainly by vasopressin.

26
Q

Where is vasopressin and produced and released?

A

Produced by hypothalamic neurons and released from the posterior pituitary.

27
Q

Vasopressin couples to […]

A

GPCR V1 (smooth muscle) and V2 (kidney)

28
Q

What is the effect of vasopressin? Where on the tubule are they placed?

A

It stimulates the insertion of aquaporins in the luminal (apical) membrane of the collecting duct cells and increases their water permeability.

29
Q

When vasopressin is present, the collecting ducts become [more/less/non] permeable to water, leading to water […]. When vasopressin is absent, the collecting ducts become [more/less/non] permeable to water, leading to water […].

A

More, reabsorption
Non, diuresis

30
Q

The malfunction of the vasopressin system leads to the condition […]

A

Diabetes insipidus

31
Q

How does the effect of vasopressin vary between the cortical and medullary collecting duct?

A

In the cortex, the osmolarity doesn’t change much even with the change in water because the surrounding osmolarity is quite normal. But as you move into the medullary connecting duct, the water movement outwards really starts to increase the concentration of the urine.

32
Q

What are the two mechanisms regulating vasopressin secretion? Which is more important?

A
  1. Osmoreceptor control (most important)
  2. Baroreceptor control (less sensitive)
33
Q

Describe the osmoreceptor control of vasopressin secretion.

A
  • Excess H2O ingested
  • Decreased body fluid osmolarity
  • Decreased firing by hypothalamic osmoreceptors
  • Decreased vasopressin secretion by posterior pituitary
  • Decreased plasma vasopressin
  • Decreased permeability to H2O in collecting duts
  • Decreased H2O reabsorption
  • Increased H2O excretion
34
Q

Describe the baroreceptor control of vasopressin secretion.

A
  • Decreased plasma volume
  • Decreased venous, atrial, and arterialpressures
  • Increase in vasopressin secretion in posterior pituitary due to reflexes mediated by cardiovascular baroreceptors
  • Increased plasma vasopressin
  • Increased tubular permeability to H2O in collecting ducts
  • Increased H2O reabsorption
  • Decreased H2O excretion
35
Q

When is the baroreceptor control of vasopressin important?

A

It is a safety net after the osmoreceptor control, if plasma volume gets really low.

36
Q

Name 4 factors that affect how we feel thirst. Include the direction of their effect.

A
  1. Decreased plasma volume - activates baroreceptors, which directly increases thirst, and this also increases angiotensin 2, which increases thirst.
  2. Increased plasma osmolarity - activates osmoreceptors, which increases thirst
  3. Dry mouth and throat - increases thirst
  4. Metering of water intake by GI tract - decreases thirst
37
Q

How does the thirst center change with age? What is the significance of this?

A

This thirst center gets less sensitive as you age. This is particularly important in hot areas, as people might not feel compelled to drink to correct their osmolarity.

38
Q

Describe the body’s response to severe sweating.

A
  • Severe sweating
  • Loss of hypoosmotic salt solution (loss of water > loss of Na+)
    • Decreased plasma volume
    • Decreased GFR
    • Increased plasma aldosterone
    • Increased plasma vasopressin
      - Decreased sodium excretion
    • Increased plasma osmolarity
    • Increased plasma vasopressin
    • Decreased H2O excretion

PHGY 210 (36 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions