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HUBS192 2022 > lecture 33 - body water distribution & regulation > Flashcards

lecture 33 - body water distribution & regulation Flashcards

1
Q

What proportion of total body water is made up of Intracellular fluid?

A

2/3

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2
Q

What proportion of total body water is made up of extracellular fluid?

A

1/3

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3
Q

What are the components of Extracellular fluid?

A

Plasma and interstitial fluid

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4
Q

What proportion of ECF is plasma?

A

1/5

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5
Q

What proportion of ECF is interstitial fluid?

A

4/5

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6
Q

What factor will typically change the osmolarity of the ECF?

A

A change in the amount of water in the ECF

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7
Q

How does dehydration affect plasma osmolarity?

A

Decrease in water causes an increase in plasma osmolarity

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8
Q

How does hyper-hydration affect plasma osmolarity?

A

Decreases osmolarity as there is an increase in water

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9
Q

What happens to the balance of water in ICF and ECF if there is the loss of water only from the ECF?

A

The ECF will have a greater osmolarity than the ICF, so there is an osmotic gradient pushing water from the ICF to ECF, so that cells shrink

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10
Q

What happens to the balance of water in ICF and ECF when there is the loss of isosmotic fluid from the ECF?

A

The ECF will have the same osmolarity as the ICF still, so there will be no shift of water, and cells will remain the same volume

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11
Q

What happens to the balance of water in ICF and ECF if there is the gain of water only to the ECF?

A

The ECF will have a lesser osmolarity than the ICF, so there is an osmotic gradient pushing water from the ECF to ICF, so that cells swell

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12
Q

What happens to the balance of water in ICF and ECF when there is the gain of isosmotic fluid to the ECF?

A

The ECF will have the same osmolarity as the ICF still, so there will be no shift of water, and cells will remain the same volume

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13
Q

What are the 3 parts of the nephron where water is reabsorbed?

A

The proximal convoluted tubule, descending limb of the nephron loop, collecting duct

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14
Q

Where is the majority (67%) of water in the filtered load reabsorbed in the nephron?

A

Proximal convoluted tubule

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15
Q

What are the 2 types of reabsorption in the nephron?

A

Bulk and regulated reabsorption

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16
Q

What is bulk reabsorption?

A

Unregulated/obligatory/automatic reabsorption

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17
Q

What is regulated reabsorption?

A

Facultative reabsorption that is regulated by hormones, e.g. ADH

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18
Q

What percentage of water in the filtered load undergoes bulk reabsorption?

A

92%

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19
Q

Where does bulk reabsorption of water occur?

A

In the proximal convoluted tube and descending nephron loop

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20
Q

What type of epithelia enables bulk reabsorb on of water in the nephron?

A

Leaky epithelia - allow for paracellular transport

21
Q

What type of absorption occurs in bulk reabsorption of water?

A

Trans- and para-cellular reabsorption

22
Q

What regulates regulated/facultative reabsorption of water?

A

Anti-diuretic hormone

23
Q

What type of absorption occurs in the regulated reabsorption of water?

A

Trans cellular reabsorption

24
Q

Where does regulated water reabsorption occur in the nephron?

A

In the collecting duct

25
Q

Where is sodium reabsorbed in the nephron?

A

Proximal convoluted tubule, ascending limb of the nephron loop, distal convoluted tubule, collecting duct

26
Q

Where is the majority (67%) of sodium reabsorbed in the nephron?

A

The proximal convoluted tubule

27
Q

Where does bulk sodium reabsorption occur?

A

In the proximal convoluted tubule and ascending nephron loop

28
Q

Where does regulated sodium reabsorption occur?

A

The distal convoluted tubule and collecting duct

29
Q

What is regulated sodium reabsorption regulated by?

A

Aldosterone (RAAS)

30
Q

What is water reabsorption in the proximal tubule driven by?

A

Na+ reabsorption

31
Q

How does sodium aid in glucose reabsorption in the proximal convoluted tubule?

A

Uses its concentration gradient to bring glucose into epithelial cells via sodium-glucose contransporter. Glucose can then diffuse out into the peritubular fluid then into capillaries. Na+ gradient maintained by Na+/K+ ATPase

32
Q

How does chloride get reabsorbed in the proximal convoluted tubule?

A

Via the paracellular pathway, down its concentration gradient

33
Q

What is the ascending nephron loop permeable to?

A

Sodium

34
Q

What is the descending nephron loop permeable to?

A

Water

35
Q

What are the 2 modes of reabsorption of water in the descending loop?

A

Transcellular - aquaporins, paracellular

36
Q

What is generated inside the nephron by the reabsorption of sodium into the interstitial fluid around the ascending nephron loop?

A

A Hyper-Osmotic Medullary Gradient (HOMG)

37
Q

What does HOMG stand for?

A

Hyper-Osmotic Medullary Gradient

38
Q

What generates a HOMG?

A

The reabsorption of Na+ from the ascending nephron loop into the interstitial fluid surrounding the ascending and descending nephron loop, as well as the reabsorption of water. This leaves the bottom of the nephron loop with low water and high sodium concentration - hyper osmotic

39
Q

What type of reabsorption occurs in the collecting duct during the regulated absorption of water?

A

Only transcellular reabsorption

40
Q

What detects changes in plasma osmolarity?

A

Osmoreceptors in the hypothalamus

41
Q

Where are osmoreceptors detecting changes in plasma osmolarity located?

A

The hypothalamus

42
Q

What does the detection of plasma osmolarity by the hypothalamus stimulate?

A

Stimulates the pituitary gland to secrete more or less ADH (anti-diuretic hormone)

43
Q

How doe ADH act on a cellular level to alter reabsorption of water in the kidneys?

A

Increases the permeability of collecting duct (CD) cells by inserting aquaporin to balance a change in TBW by retaining water via reabsorption

44
Q

If total body water decreases, is ADH secretion increased or decreased?

A

Increased

45
Q

What is released if there is an increase in ECF volume and Na+ gain?

A

ANP - increases sodium secretion by reducing reabsorption

46
Q

What is released if there is a decrease in ECF volume and a loss of Na+?

A

RAAS activated and aldosterone released from the adrenal glands

47
Q

What is the cellular effect of aldosterone in the kidneys?

A

Addition of sodium channels in the apical membrane of collecting duct cells

48
Q

What is the affect of aldosterone on sodium and water absorption?

A

Both increase

HUBS192 2022 (38 decks)

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