Hormonal Regulation of Body Fluid Osmolarity Flashcards Preview

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Flashcards in Hormonal Regulation of Body Fluid Osmolarity Deck (54)
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1

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

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

2

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

Evaporation from skin cells and respiration as well as sweat

3

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

Insensible water loss

4

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

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

5

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

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

6

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

Intracellular fluid (ICF) and extracellular fluid (ECF)

ICF = around 28 L
ECF = around 14 L

7

How is total blood water measured?

Using D2O

8

What type of cells have comparatively low amounts of water?

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

9

What is the normal osmolarity in the body?

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

10

What happens when water intake exceeds loss?

Positive water balance exists

11

What happens when water loss exceeds intake?

Negative water balance exists

12

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

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

13

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

The kidneys produce a large volume of hyposmotic urine.

14

What is the major determinant of plasma osmolality?

Na+

15

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

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

16

Where is antidiuretic hormone (ADH) produced?

Ii is produced in neuroendocrine cells as a preprohormone.

17

What does the ADH preprohormone consist of?

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.

18

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

-Osmolality of plasma
-Volume and pressure of vascular system

19

What is the function of the hypothalamic osmoreceptor?

Stimulates ADH release

20

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

Inhibit ADH release

21

What is the target of ADH?

ADH receptors in the distal tubule and the collecting duct

22

What is the effect of ADH?

It leads to increase reabsorption of water into the medulla

23

How does nicotine affect ADH?

Stimulates ADH release

24

How does angiotensin II affect ADH?

Stimulates ADH release

25

How does atrial natriuretic peptide affect ADH?

Inhibits ADH release

26

How does ethanol affect ADH?

Inhibits ADH release

27

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

ADH is released at 280 mOsm/L
Thirst occurs at 298 mOsm/L

28

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

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

29

What is the effect of ADH on the collection duct?

It increases the water permeability of the collecting duct

30

How does ADH increase the water permeability of the CD?

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

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