Body fluid compartments and challenges to homeostasis

Question 1

what is osmolarity?

Answer 1

The concentration in a solution of osmotically activated particles

Question 2

What 2 factors do you need to calculate osmolarity?

Answer 2

Molar concentration of solution and number of osmostically active particles

Question 3

what is the difference between osmolarity and osmolatity?

Answer 3

-Osmolatity units are ormolu by kg of water instead of mosmol/l

Question 4

What is tonicity?

Answer 4

the effect a solution has on the volume of a cell

Question 5

What 3 types of tonicity can a solution have?

Answer 5

Isotonic – no impact on cell volume
Hypotonic- increase in cell volume
Hypertonic- decrease in cell volume

Question 6

what can a hypotonic solution result in?

Answer 6

Cell lysis

Question 7

Why do females have less total body water weight?

Answer 7

more adipose tissue and fat cells have very little water

Question 8

What are the two major components of total body water?

Answer 8

Intracellular fluid (67%) and extracellular fluid (33%)

Question 9

what does the extracellular fluid include?

Answer 9

Plasma (~20% of ECF)
Interstitial fluid (~80% of ECF)
Lymph (negligible) + Transcellular fluid (negligible)

Question 10

What can be used to measure these fluids?

Answer 10

Tracers - specific chemicals that can be used to determine the distribution volume

Question 11

Name some useful tracers?

Answer 11

TBW: 3H2O
ECF: Inulin
Plasma: labelled albumin

Question 12

what is the equation for working out the volume using a tracer?

Answer 12

V(litres)= Dose (D)/ sample conc (C)

Question 13

what is homeostasis?

Answer 13

Maintaining a stable internal environment

Question 14

How is homeostasis achieved?

Answer 14

input(s) = output (s)

Question 15

What is insensible loss?

Answer 15

loss of water over that we have no physiological control of body i.e diffusion of water across the surface of our skin

Question 16

What is sensible loss?

Answer 16

Output of water that we have some control over i.e sweat / urine

Question 17

During hot weather or prolonged heavy exercise , how is water balance maintained?

Answer 17

Water balance is maintained by increased water ingestion. Decreased excretion of water by the kidneys alone is insufficient to maintain water balance

Question 18

where is there always a higher concentration sodium and chloride ions?

Answer 18

extracellular fluid

Question 19

where is there always higher concentration of potassium ions?

Answer 19

intracellular fluid

Question 20

what is plasma and interstitial fluid separated with?

Answer 20

capillary wall

Question 21

what is interstitial fluid and intracellular fluid separated by?

Answer 21

plasma membrane

Question 22

What allows cells to maintain internal environments that differ in composition compared to their surroundings?

Answer 22

cell membrane and membrane transport mechanisms

Question 23

how do osmotic concentrations of ECF and ICF differ and why?

Answer 23

• osmotic concentrations are identical
• Because changes in solute concentrations lead to immediate changes in water distribution, the regulation of fluid balance and electrolyte balance are tightly intertwined

Question 24

what is fluid shift?

Answer 24

Movement of water between the ICF and ECF in response to an osmotic gradient

Question 25

What happens if osmotic concentration of the ECF increase because of dehydration?

Answer 25

Lost more water than you should, salt concentration of extracellular fluid increased, extracellular fluid is hypertonic compared to inside the cell , water move out cell to ECF to restore osmotic equilbirum

Question 26

what happens if osmotic concentration of the ECF decreases because of overhydration?

Answer 26

Added more water to ECF, more water outside the cell than inside , water moves in and increases cell volume

Question 27

what are the 3 challenge to fluid homeostasis?

Answer 27

1. gain or loss of water
2. gain or loss of NaCl
3. gain or loss of isotonic fluid

Question 28

what causes the gain or loss of NaCl?

Answer 28

Na+ “excluded” from ICF (recall ion distributions)
(b) Osmotic water movements

These two factors combine to produce opposite changes in ICF and ECF volumes

Question 29

what alters composition and volume of ECF?

Answer 29

kidneys

Question 30

why Is regulation of ECF volume vital?

Answer 30

Vital for long term regulation of blood pressure

Question 31

How is electrolyte balance maintained?

Answer 31

when rates of gain = rates of loss

Question 32

why is electrolyte balance important?

Answer 32

1) Total electrolyte concentrations can directly affect water balance
2) The concentrations of individual electrolytes can affect cell functions

Question 33

why are Na+ and K+ important?

Answer 33

a) They are major contributors to the osmotic concentrations of the ECF and ICF, respectively
b) They directly affect the functioning of all cells

Question 34

what does the presence of sodium salts result to?

Answer 34

90% of the osmotic concentration of the ECF

Question 35

what plays a key role in establishing membrane potential ?

Answer 35

K+

Question 36

small leakages or uptake may severally affect K+ plasma leading to what ?

Answer 36

• muscle weakness - paralysis

- cardiac irregularities- cardiac arrest

Question 37

what is salt imbalance a result of?

Answer 37

Changes in extracellular fluid volume