Physiology - Body Fluid Compartments

Question 1

How much of total body weight is water?

Answer 1

60% (42L)

Question 2

How much of total body water is intracellular fluid?

Answer 2

2/3 (28L)

Question 3

How much of total body water is extracellular fluid?

Answer 3

1/3 (14L)

Question 4

Describe the division of extracellular fluid

Answer 4

Interstitial fluid - 11L

Plasma - 3L

Question 5

What is the formula for concentration?

Answer 5

Concentration = mass / volume

Question 6

Describe how adipose tissues has an effect on total body water?

Answer 6

Adipose tissues contains less water than non-adipose tissue

Question 7

Why do men have more body water than women?

Answer 7

Since women tend to have more adipose tissue than men

i.e. adipose tissue = less water then non-adipose tissue

Question 8

Why do babies have a large amount of body water in proportion to body weight when they are born?

Answer 8

Since they have less adipose tissue

Question 9

Define osmolality

Answer 9

osmolality = osmoles / Kg H2O

Question 10

Why are volumes and concentrations stable in health humans?

Answer 10

Since the intracellular and extracellular compartments are in equilibrium

Question 11

Describe the effect a hypertonic extracellular environment on cells?

Answer 11

Cells shrink

Question 12

Describe the effect a hypotonic extracellular environment on cells?

Answer 12

Cells swell

Question 13

What does ADH do and how does it exert it’s effect?

Answer 13

Controls plasma osmolality by regulating absorption of water

• ADH increases the permeability of water in the last 1/3 of the distal tubule and the collecting duct

Question 14

What is being sensed in osmoregulation?

Answer 14

Plasma osmolality

Question 15

What is the sensor in osmoregulation?

Answer 15

Hypothalamic osmoreceptors

Question 16

What are the factors that have an effect on osmoregulation?

Answer 16

ADH

Thirst

Question 17

How do ADH and thirst play a part in osmoregulation?

Answer 17

ADH => controls water excretion

Thirst => controls water intake

Question 18

Which things can suppress ADH?

Answer 18

Atrial natriuretic peptide (released in hypo-osmolality)

Ethanol

Question 19

What is being sensed in volume regulation?

Answer 19

Effective circulating volume

Question 20

What are the sensors in volume regulation?

Answer 20

Atria

Carotid sinus

Afferent arteriole

Question 21

Which things can have an effect on volume regulation?

Answer 21

RAA system

Sympathetic activity

Pressure natriuresis

ANP

ADH

Question 22

What is effected in controlling volume regulation?

Answer 22

Urine Na+ excretion

Question 23

What is the main action of the RAA system?

Answer 23

System increases blood pressure and volume

Question 24

What does angiotensin II do?

Answer 24

stimulates aldosterone
- by acting on zona glomerulosa of adrenal cortex

Stimulates secretion of ADH

Causes artery constriction => increase blood pressure

Decreases GFR => retain water

Increases thirst

Question 25

How does aldosterone promote sodium reuptake?

Answer 25

By stimulating the production of sodium channels in the distal tubules of the nephron => increased reabsorption

Question 26

When is ANP secreted and how does ANP work?

Answer 26

Responds to increased BP in the right atrium

Secretes ANP

ANP increases Na+ excretion => increased water loss

=> Decreased BP

Question 27

Which four forces are involved in starling’s law?

Answer 27

Capillary hydrostatic pressure
Capillary oncotic pressure

Interstitial hydrostatic pressure
Interstitial oncotic pressure

Question 28

List some of the crystalloid fluid solutions used in medical practice

Answer 28

0.9% NaCl

Hartmann’s solution

5% Dextrose

Various combinations of dextrose and NaCl

Question 29

List some of the colloid fluid solutions used in medical practice

Answer 29

Gelatin polymers

Hydroxyethyl starch

Human albumin

Question 30

What is the formula for clearance of a substance?

Answer 30

(Urine concentration x Amount of urine produced per min) / Plasma Concentration