Brainscape's Knowledge GenomeTM

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


See full index

Class 3 > Lecture 33: Body Water - Distribution and Regulation > Flashcards

Lecture 33: Body Water - Distribution and Regulation Flashcards

1
Q

What three things is renal filtration defined by?

A

renal blood flow
filtration barrier
driving forces

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

What is the equation for renal clearance?

A

Cs = (Us x V)/Ps

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

What substance is used to estimate GFR?

A

creatinine

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

What is GFR?

A

a specific case of clearance

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

What is the clearance detecting and how did we get there?

A

We have a specific concentration of a substance in the plasma and a certain volume of urine per time, and we are detecting the concentration of the substance in urine - this makes up the volume of plasma that has been cleared

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

What is the filtration fraction and how can it be calculated?

A

it is how much blood in the kidney is actually filtered and it defines the ratio between perfusion and filtration in the kidney (GFR/RPF)

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

What is the filtered load and how can it be caculated?

A

the amount of substance filtered per time (GFR x Ps)

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

Why is water homeostasis so important?

A

Because it is needed to maintain blood pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the two main reasons for maintaining blood pressure?

A

we need to get nutrients to the tissues and to get CO2 out

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

What percentage of out total body weight does water take up?

A

55-60%

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

What percentage of our total body weight does ECF make up?

A

33%

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

What percentage of our total body weight does ICF make up?

A

66%

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

What does the ECF consist of and what percentage of the ECF do these two things make up?

A
  • plasma (20% of the ECF)

- interstitial fluid (80% of the ECF)

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

What is meant by the ICF?

A

The fluid inside the cells

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

What is meant by the interstitial fluid?

A

the fluid in between the cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Define osmolarity

A

the concentration of a solution expressed as the total number of solute particles per litre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is osmolarity based on?

A

the number of osmotically active ions or solutes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How osmotically active is 145 mM NCl?

A

145 mM Na+ + 145 mM Cl- = 290 m osmol/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How osmotically active is 145 mM glucose?

A

145 m osmol/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does osmolarity and spez gravity relate to each other? How do they differ?

A

Osmolarity measures the osmotic activity of ions or solutes whereas spez gravity measures the density of the solution. Spez gravity is just an estimate of osmolarity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Using NaCl and glucose as an example, define isosmotic

A

isosmotic means they have the same osmolarity

for example, 145 mM of NaCl has the same osmolarity as 290 mM glucose (290 m osmol/L)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Using NaCl and glucose as an example, define hyposmotic

A

hyposmotic means one has a lower osmolarity

for example, 145 mM of glucose has a lower osmolarity as 145 mM NaCl (145 m osmol/L vs 290 m osmol/L)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Using NaCl and glucose as an example, define hyperosmotic

A

hyperosmotic means one has a higher osmolarity

for example, 145 mM of NaCl has a higher osmolarity as 145 mM glucose (290 m osmol/L vs 145 m osmol/L)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Define tonicity

A

The measure of the osmotic pressure gradient between two solutions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is tonicity based on?

A

the effect of a solution of cells

26
Q

What does an isotonic solution not change?

A

is does not change the water homeostasis between the ECF and ICF

27
Q

Despite the ECF and ICF having different concentrations of ions and different pH values, what is always kept in balance?

A

the osmolarity

28
Q

What are the three main ways we intake water?

A

food
ingested fluid
water formed by catabolism

29
Q

What is our main output of water?

A

urine from the kidneys

30
Q

In order to reabsorb water, what first needs to be reabsorbed?

A

Na+

31
Q

What are the four important places within the nephron where sodium is reabsorbed, in order?

A

PCT (67%)
TAL (25%)
DCT (5%)
CD (3%)

32
Q

What percentage of Na+ is reabsorbed?

A

99%

33
Q

What are the three important places within the nephron where water is reabsorbed, in order?

A

PCT (67%)
tDL (25%)
CD (2-8%)

34
Q

Describe the reabsorption of water (and hence, Na+) in the proximal tubule

A

Na+ flows through the leaky cuboidal epithelium down its concentration gradient into the cells which decreases the local osmolarity in the tubular lumen and so h2o enters the cell. It does this via osmosis through aquaporins (transcellular) and via very leaky tight junctions (paracellular)

35
Q

How is glucose related to the reabsorption of water?

A

transporters such as the sodium glucose transporter use the sodium gradient to reabsorb glucose

36
Q

How does the absorption of water differ between different parts of the nephron loop?

A

The descending limb is permeable to water but impermeable to solutes. Solutes remain as water leaves, so the tubular fluid reaching the turn of the nephron loop has a higher osmotic concentration that it did at the start.
The ascending limb is impermeable to water and other solutes and selectively to Na+ and Cl-.

37
Q

Water reabsorption in the nephron loop is the same as/higher than/lower than sodium reabsorption?

A

the same as

38
Q

Changing water contents changes

A

osmolarity

39
Q

How does the fluid shift due to changes in osmolarity?

A

fluid shifts between the ECF and ICF to equalise

40
Q

Changing water content changes

A

cell size

41
Q

Describe what happens to the flow of water in RBC when the cells are in a hypertonic environment

A

there is a higher concentration of solutes outside the cell than inside the cell so water flows out of the cell which means they gets smaller

42
Q

Describe what happens to the flow of water in RBC when the cells are in a hypotonic environment

A

there is a higher concentration of solutes inside the cell than outside the cell so water flows into the cell which means they gets larger and can burst

43
Q

Describe what happens to the flow of water in RBC when the cells are in an isotonic environment

A

there is an equal flow of water into and out of the cells

44
Q

Describe the changes in body osmolarity when we are dehydrated?

A

There is a water loss from the ECF only so the ECF osmolarity increases (gets more concentrated with solute). Water moves out of the cell until the ICF and ECF are osmotically balanced but the cells will get smaller

45
Q

Describe the changes in body osmolarity when we are hyperhydrated?

A

There is a water gained from the ECF only so the ECF osmolarity decreases (gets less concentrated with solute). Water moves into the cell until the ICF and ECF are osmotically balanced but the cells will get larger

46
Q

What hormone regulates body osmolarity?

A

ADH

47
Q

Describe the activation of ADH if ECF osmolarity changes

A
  • changes in plasma (ECF) osmolarity are detected by osmoreceptors in the hypothalamus
  • this stimulates the pituitary gland to secrete more/less ADH
  • ADH alters permeability of the renal collecting duct
48
Q

Does ADH increase or decrease permeability of the renal collecting duct? How would ADH secretion be different when we are hyperhydrated or dehydrated?

A

ADH increases the permeability of the collecting duct so ADH secretion would decrease if we were hyperhydrated by increase if we were dehydrated

49
Q

Where is ADH made and where is it released?

A

ADH is made in the cell body of central neurons in the hypothalamus and is transported via axons to the posterior pituitary gland and it is released from here into the bloodstream

50
Q

What are the two main stimuli for the release of ADH?

A
  1. increased ECF osmolarity

2. decreased blood volume

51
Q

What is the action of ADH?

A

it inserts water channels (aquaporins) in the luminal membrane of CD to increase H2O reabsorption in the collecting duct

52
Q

What are the two types of water absorption in the nephron?

A

obligatory and facultative

53
Q

Where does obligatory water regulation take place? Is it regulated? It accounts for what percentage of the total water reabsorption?

A
  • in the PCT and nephron loop
  • no it is not regulated
  • 92%
54
Q

Where does facultative water regulation take place? Is it regulated? It accounts for what percentage of the total water reabsorption?

A
  • in the DCT and collecting duct
  • regulated by ADH
  • accounts for up to 8%
55
Q

Facultative water reabsorption occurs via ______ epithelia and only occurs ____cellularly

A

tight

trans

56
Q

Describe the water reabsorption in the CD without ADH

A

Water is not reabsorbed in the DCT or the CD so all the fluid reaching the DCT is lost in the urine. No facultative water reabsorption occurs, and the person then produces large amount of very dilute urine

57
Q

What is diuresis? Does this happen with or without ADH?

A
  • excessive production of urine

- without ADH

58
Q

What is anti-diuresis? Does this happen with or without ADH?

A
  • reduced production of urine

- with ADH

59
Q

Describe the water reabsorption in the CD with ADH

A

ADH finds its receptor o the basolateral side of the CD cells. This, via intracellular signalling cascades, causes aquaporins to appear in the apical surfaces of the plasma membranes lining the DCT and CD. This increases the absorption of water and the result is very concentrated urine

60
Q

What are aquaporins?

A

water channels

Class 3 (41 decks)

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