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Physiology > Hormonal Regulation of Body Fluid Osmolarity > Flashcards

Hormonal Regulation of Body Fluid Osmolarity Flashcards

1
Q

What is the importance of the kidneys in elimination of water from the body?

A

They are the major route for water elimination from the body.

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2
Q

What are the other methods of water loss from the body?

A

Evaporation from skin cells and respiration as well as sweat

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3
Q

What is the loss of water through evaporation from skin cells and respiration referred to as?

A

Insensible water loss

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4
Q

Besides, sweat and respiration, where else can water loss occur?

A

Fecal water loss, however, this is relatively small unless there is diarrhea.

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5
Q

What is the average amount of total body water in a person?

A

42L which can be 50-70% of total body mass

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6
Q

What are the two major components of the total body water?

A

Intracellular fluid (ICF) and extracellular fluid (ECF)

ICF = around 28 L
ECF = around 14 L
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7
Q

How is total blood water measured?

A

Using D2O

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8
Q

What type of cells have comparatively low amounts of water?

A

Fat cells. They are only 10% water due to their hydrophobicity.

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9
Q

What is the normal osmolarity in the body?

A

It is around 300 mOsm/L. This is found by 2*[Na+] which is around 290 mOsm/L

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10
Q

What happens when water intake exceeds loss?

A

Positive water balance exists

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11
Q

What happens when water loss exceeds intake?

A

Negative water balance exists

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12
Q

What happens to the urine produced when water is low or is lost?

A

The kidneys will produce a small volume of hyper osmotic urine.

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13
Q

What happens to the urine produced when there is high water intake?

A

The kidneys produce a large volume of hyposmotic urine.

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14
Q

What is the major determinant of plasma osmolality?

A

Na+

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15
Q

Is water balance control dependent upon the control of other solutes?

A

No. The kidneys can control water excretion independently of the excretion of K+, Na+ and urea.

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16
Q

Where is antidiuretic hormone (ADH) produced?

A

Ii is produced in neuroendocrine cells as a preprohormone.

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17
Q

What does the ADH preprohormone consist of?

A

It consist of a signal peptide, ADH, neueophsin and copeptin (glycopeptide). Cleavage of the signal and further processing turns it into ADH and put into secretory granules in the posterior pituitary gland.

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18
Q

What are the physiological regulators of the negative feedback system of body fluid control?

A
  • Osmolality of plasma

- Volume and pressure of vascular system

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19
Q

What is the function of the hypothalamic osmoreceptor?

A

Stimulates ADH release

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20
Q

What is the function of the aortic and carotid baroreceptors in regards to body fluid regulation?

A

Inhibit ADH release

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21
Q

What is the target of ADH?

A

ADH receptors in the distal tubule and the collecting duct

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22
Q

What is the effect of ADH?

A

It leads to increase reabsorption of water into the medulla

23
Q

How does nicotine affect ADH?

A

Stimulates ADH release

24
Q

How does angiotensin II affect ADH?

A

Stimulates ADH release

25
Q

How does atrial natriuretic peptide affect ADH?

A

Inhibits ADH release

26
Q

How does ethanol affect ADH?

A

Inhibits ADH release

27
Q

What is the sensitivity level of ADH stimulus to changes in plasma osmolality for release?

A

ADH is released at 280 mOsm/L

Thirst occurs at 298 mOsm/L

28
Q

What is the sensitivity level of ADH stimulus to changes in blood pressure or volume for release?

A

It is fairly sensitive and is released when pressure reaches 90% of normal

29
Q

What is the effect of ADH on the collection duct?

A

It increases the water permeability of the collecting duct

30
Q

How does ADH increase the water permeability of the CD?

A

ADH receptor activation leads to the insertion of aquaporin 2 water channels which increases the permeability of water passively

31
Q

What effect does ADH have on urea?

A

It increases the urea permeability of the lower collecting duct ONLY. Urea also lacks active transport mechanisms like water does.

32
Q

What is the activation pathway of the ADH?

A

ADH -> ADH Receptor -> Gs protein -> Increased cAMP -> PKA -> Insertion of Aquaporin-2 -> Increased water permeability

33
Q

What happens to the fluid in the case of diarrhea and what is this an example of?

A

Isosmotic Volume Contraction

ECF would decrease with everything else constant

34
Q

What happens to the fluid in the case of water deprivation and what is this an example of?

A

Hyperosmotic Volume Contraction

Both ICF and ECF shrink and the overall osmolality increases

35
Q

What happens to the fluid in the case of adrenal insufficiency and loss of salt and what is this an example of?

A

Hyposmotic Volume Contraction

ECF would shrink into the ICF and ICF would increase but the overall osmolality decreases

36
Q

What happens to the fluid in the case of infusion of saline and what is this an example of?

A

Isosmotic volume expansion

The ECF would increase with everything else constant

37
Q

What happens to the fluid in the case of drinking seawater and what is this an example of?

A

Hyperosmotic volume expansion

It would increase the fluid in the ECF and decrease the ICF as it flows into the ECF. The overall osmolality is increased.

38
Q

What happens to the fluid in the case of syndrome of inappropriate ADH and what is this an example of?

A

Hyposmotic volume expansion

The ECF volume will increases and it will shift into the ICF and increase it as well. The overall osmolality decreases though.

39
Q

How does the renin-angiotensin-aldosterone system work?

A

When the JGA detects low BP or blood volume the kidney will secrete renin which turns angiotensinogen into angiotensin-I and ACE turns it into angiotensin-II. It leads to increased water and salt reabsorption.

40
Q

How does the ADH system work?

A

When hypothalamus detects an increase in the osmolarity ADH is released to increase the reabsorption of water.

41
Q

Where is the site of action of mannitol?

A

2nd half of PT

42
Q

Where is the site of action of acetazolaminde?

A

1st half of PT

43
Q

Where is the site of action of furosemide?

A

Thick Ascending LoH

44
Q

Where is the site of action of hydrochlorothiazide?

A

Distal Convoluted Tubule

45
Q

Where is the site of action of spironolactone?

A

Distal Convoluted Tubule and Collecting Duct

46
Q

Where is the site of action of amiloride?

A

Collecting Duct

47
Q

Where is the site of action of triamterene?

A

Collecting Duct

48
Q

What is the effect of mannitol on K?

A

Wasting

49
Q

What is the effect of acetazolamide on K?

A

Wasting

50
Q

What is the effect of furosemide on K?

A

Wasting

51
Q

What is the effect of hydrochlorothiazide on K?

A

Wasting

52
Q

What is the effect of spironolactone on K?

A

Sparing

53
Q

What is the effect of amiloride on K?

A

Sparing

54
Q

What is the effect of triamterene on K?

A

Sparing

Physiology (81 decks)

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